ABSTRACT. Introduction The Neogene and Quaternary sediments of Macedonia and Thrace lie unconformably over the folded alpine basement and are of fluvial, lacustrine or marine origin. These sediments are deposited into grabens or other neotectonic basins and are not connected to orogenetic procedures. The Post Alpine formations are widespread and are characterized by a wide lithological and facies variation. The Holocene sedimentation in the eastern Mediterranean is strongly affected by changes in the sea surface level associated with global paleoclimatic changes at the end of the Quaternary (Mountrakis, 2010). The area of Macedonia and Thrace is a complex of grabens and horsts arranged in a NW-SE trend. Intermountain high level basins with elevation 400-500 m or low level basins with elevation 150-250 m, large coastal basins and plains were filled with Neogene and Quaternary sediments. Red beds are the most characteristic of them. They can be traced in the subsurface of the central parts of the basins. The widespread red beds and the associated rich mammalian fauna offer a good basis for stratigraphic and paleogeographic correlation with other sedimentary deposits in the Mediterranean (Psilovikos et al., 1987). The coastline of Macedonia and Thrace incorporates the mouths of many small and large rivers. Most of them drain the mainland, except Evros, Nestos, Strymon and Axios that expand their network to neighboring countries. Evros River is the largest supplier of continental clastic material (8.5 × 106 tons/year) in the coastal region of NE Aegean. Similarly, in the Thermaikos Gulf, the rivers Gallikos, Axios, Aliakmon and Pinios discharge (25-30) × 106 tons/year of clastic terrestrial material (Poulos et al., 2000). The total suspended material in the NW Aegean is (484-830) × 103 tons/year (Karageorgis & Anagnostou, 2003).

Results and discussion The fluvial sediments are climatically uniform in their setting and prograding into the north Aegean Sea. Tidal activity is negligible and the waves play a secondary role compared to the high sediment discharge of the rivers. Sand is the predominant (>60%) constituent of the river mouths (top sets), while the prodelta area consists mainly of silt- and clay-sized (>70%) particles (Poulos & Chronis, 1997). The extended presence of quartz, feldspars and micas in the discharged material of the Evros is expected because it constitutes the weathering products of the large drainage basin of the river (extended in NE Greece and south Bulgaria), where igneous and metamorphic rocks predominate. The presence, in significant amounts, of zeolites is justified by the extended presence of volcaniclastic sediments in this drainage basin (Tsirambides & Kantiranis, 1998). Evros is the largest supplier of fine grained Fe-Al-rich continental detritus to the offshore area. The modern sediments of the Alexandroupolis Gulf have adopted their characteristic zonal distribution in response to the coastal topography, the water motion and the quality of the supplied material. Acid and mafic igneous (especially volcanic), as well as metamorphic rocks cover the western and central parts of the Evros river drainage basin; Neogene sediments cover the eastern part and the coastal zone (Perissoratis et al., 1987). The abundance of illite and smectite in the offshore sediments is mainly due to the weathering of primary Fe-Mg minerals of the drainage basin rocks and their transport and deposition in the Gulf. Especially, the abundance of smectite is enhanced by the high Fe and organic content, which results in a rapid flocculation and settling out of smectite grains. Kaolinite content expresses the strong climatic dependence controlled by the intensity of hydrolysis of continental rocks which occur in the drainage basin. However, the low content of kaolinite may be due to unfavorable climatic and physicochemical conditions, as well as to the detrital origin, rapid transport and deposition of the weathered material in the Gulf. Furthermore, the low percentage of the interstratified illite/smectite, as well as some presence of amphiboles in the clay fraction of the discharged material, confirm the limited reworking and weathering of the primary ferromagnesian minerals because of the high river discharge over short time periods and rapid deposition in the Gulf (Pehlivanoglou et al., 2000). The most likely source materials for the formation of red beds at the Cedar Hills of Thessaloniki are feldspars, micas, and various Fe-Mg silicates, which are primary constituents of the metamorphic and ultramafic rocks predominating in these hills such as the greenschists (Tsirambides, 2004). During Holocene, the rivers Gallikos, Axios, Aliakmon and Pinios discharged into the Thermaikos Gulf terrestrial clastic sediments with a mean accumulation rate 2.2 × 106 tons/yr. The maximum thickness of the sediments in the Gulf reaches 25-30 m. The estimated mean sedimentation rate ranges from 5 cm/ka to 15 cm/ka. The main minerals present in decreasing abundance are: quartz, feldspars (plagioclases > K-feldspars), Fe-Mg minerals, micas, and clay minerals. On average, the clay fraction (<2 μm) consists of: 48% illite, 26% smectite, 18% (chlorite + kaolinite), 3% quartz, 3% feldspars and 2% Fe-Mg minerals. The origin of dolomite and calcite is mostly biogenic. Ordered and randomly interstratified phases of I/S are present. The abundance of smectite is enhanced by the high Fe and organic content of the terrigenous input, as well as by the physicochemical conditions of the seawater, which result in rapid flocculation and settling of smectite flocks. The low content of kaolinite may be due to unfavorable climatic and physicochemical conditions, as well as to the detrital origin, rapid transport and deposition of the weathered material in the Gulf. Furthermore, the presence of amphiboles observed even in the coarse clay fraction (2-0.25 μm) confirms the limited reworking and weathering of the primary ferromagnesian minerals because of the high river discharge over short time periods and rapid deposition in the Gulf. Finally, the significant presence of interstratified illite/smectite confirms the limited reworking and weathering of the primary minerals during their transport and deposition from the drainage basins of the rivers to the Gulf (Lykousis et al., 1981; Lykousis & Chronis, 1989; Karageorgis & Anagnostou, 2001; Pehlivanoglou et al., 2004). The recent sediments of the Thermaikos Gulf have adopted their characteristic zone distribution in response to the coastal topography, the water circulation, and the prevailing climate in the region. The composition and dispersal of the suspended load of the rivers into the Gulf is controlled by the prevailing seasonal meteorological conditions at their catchment areas and the coastal area. The aggregation and distribution of clay particles in the Gulf is least controlled by the organic content of the terrigenous input because its presence is limited (Poulos et al., 2000).

ABSTRACT. The study area is located in Hisarlıkaya region, Southwest (SW) of Ankara, Central Anatolia. Units cropping out throughout large areas consist of different sized and shaped xenoliths having a polygenetic origin in certain areas. Macroscopically blackish-greenish-greyish-greenish colored and porphyritic textured rocks contained mainly plagioclase, amphibole, opaque microlites and rarely pyroxene crystals. Plagioclases are generally euhedral in shape and are predominantly zoned. They show sieved texture at the rims and/or cores. The amphiboles have been completely or partly replaced by Fe-Ti oxides. According to the microprobe analysis, it was determined that the plagioclases in the host rocks are andesine and the amphiboles are calcic-chermakite in characters. As a result of geochemical analyses, volcanic rocks have been identified as trachytic rocks with calc-alkaline character. Major, trace element Harker variation diagrams indicate an effective fractional crystallization process in the formation of these rocks. SiO2 (62.6-63.7%), Al2O3 (16.5-17.2 %), Na2O (4.9-5.6 %), Sr (1249-1397 ppm), Y (13.1-14.2 ppm) contents of these trachytic rocks indicate typical adakitic rocks features. Previous works in the study and vicinity areas revealed the presence of volcanic products carrying the evidences of post collisional Early Miocene magmatism. It is thought that the Hisarlıkaya volcanic rocks, having trachytic character, were formed in this period.

ABSTRACT. Volatiles are transported from the deep crust or mantle to the surface in geodynamically active areas where seismic, volcanic and geothermal activity is present; the circulation of hydrothermal fluids in the crust is enhanced. In such areas, faults may act as preferential pathways for advective gas-carrying fluid transport. Towards the surface, pressure decrease allows the gases to escape from the fluids into soil gas and eventually into the atmosphere (King, 1986). The migration of carbon-bearing crustal and mantle fluids contributes to Earth’s carbon cycle (Berner & Kothavala 2001). However, till now, the mechanisms, magnitudes and time variations of carbon transfer from depth to the surface remain the least understood parts of the global carbon budget. Carbon dioxide and methane are the main contributors of the total amount of C-degassing from geological (volcanic and non-volcanic) sources. From the beginning of the last century, high attention has been paid to the reservoirs of CO2 and CH4 in the atmosphere because they represent the most dangerous species in terms of global warning. The increased amount of carbon dioxide and methane in the atmosphere has important implications for the energy balance and the chemical composition of the atmosphere. Mörner and Etiope (2002) calculated that 102-103 Mt of CO2 are presumably involved in the carbon cycle every year. This estimation though, is affected by high uncertainty as a number of sources and C-degassing environments that account for this high leakage were not taken into consideration. Greece belongs to the most geodynamically active regions of the world and as such, it has to be considered an area of intense geogenic degassing. Regarding carbon, the territory is characterized by the high hydrothermal and volcanic activity of the South Aegean Active Volcanic Arc (SAAVA), and by widespread geological seeps of buried carbon dioxide and methane. In the present work, we present more than 700 literature data of free gases spread along the whole Hellenic territory to get insight on geographic distribution and composition of the released fluids. Moreover, we review all the published studies on CO2 and/or CH4 output of high degassing areas of Greece that are mainly concentrated along the SAAVA in a first attempt to estimate the total geologic output of the nation. Helium isotope data propose that the highest mantle contribution (50 to 90%) is found along the SAAVA, whereas the lowest in continental Greece (0-20%), with the atmospheric contribution being mostly negligible. Based on the geographical distribution of the gases, it is evident that the R/RA ratios and CO2 concentrations increase in areas characterized by: i) thin crust; ii) elevated heat flow values; iii) recent (Pleistocene-Quaternary) volcanic activity; and iv) deep routed extensional or transtensional regional faults. The highest values are therefore found along the SAAVA and the lowest in the western part of Greece where CH4 emission is prevailing. Furthermore, it was noticed that the majority of the samples present a prevailing limestone C component, whilst only few samples have a prevailing mantle C component (Sano and Marty, 1995). It seems barely possible though to distinguish CO2 deriving from crustal and slab-related limestones. Additionally, due to the complex geodynamic history, the mantle C isotope composition could be affected by subduction-related metasomatism and, similarly to the nearby Italian area (Martelli et al., 2008), the C isotope composition could be more positive. In this case, the mantle contribution is probably underestimated. In terms of geogenic carbon degassing, the best studied and most exhaling area is the SAAVA, which releases 104,090 t/a of CO2 and 20.26 t/a of CH4. Continental Greece on the contrary, is much less studied but may release CO2 in the same order of magnitude in its eastern-central and northern part. The western and south-western parts of Greece are conversely the main area of methane and higher hydrocarbon degassing. Methane output of Greece is much less constrained but the presence on its territory of one of the biggest thermogenic gas seepages of Europe releasing about 200 t/a of CH4 to the atmosphere underscores its potentially high contribution. Approximately 114,310 t/a of CO2 and 221 t/a of CH4 are released from the whole Hellenic territory (Daskalopoulou et al., submitted). This estimation though, should be considered minimum as there are processes and sources that have not been taken into consideration yet. More specifically, in the submarine manifestations found at greater depths, gases cannot reach the sea surface due to the dissolution process that takes place along the water column; this is especially true for CO2 that is more soluble in water respect to other gases (eg. Milos - Dando et al., 1995; Kolumbo - Rizzo et al., 2016 etc). Moreover, the geological and geodynamic regime can contribute in the formation of CO2 reservoirs. This is the case of Florina Basin (Pearce et al., 2004) where more than one CO2 reservoirs were created, with one of them being exploited by the company Air Liquide Greece. It is worth noting that this reservoir, found at a depth of approximately 300 m, produces 30,000 t/a of CO2 (Pearce et al., 2004). Moreover, in the same area, water is also used for water supply and irrigation purposes. This water though contains a great amount of dissolved CO2 great part of which is released to the atmosphere when the water is pumped to the surface. Another source that should be underscored is the quantification of geogenic CO2 dissolved in big karstic aquifers. Chiodini et al. (1999, 2000) demonstrated that the relatively high solubility of CO2 in water plays an important role in the quantification of carbon. This approach was proved for central Italy and it might be the case for continental Greece due to the similar geodynamic history. Finally, in ophiolitic sequences where serpentinization takes place, if and when the conditions are adequate (i.e. presence of effective catalysts – Etiope and Ionescu, 2015) an abiogenic origin for CH4 seems to be favored even at low temperatures. Ophiolitic sequences crop out widely in Greece along two N-S trending belts, whilst more hyperalkaline springs or dry seeps may be present. However, their flux in generally is very low and therefore their contribution to the total natural CH4 output has probably to be considered negligible. References Berner, R.A., Kothavala, Z., 2001. GEOCARB III: a revised model of atmospheric CO2 over Phanerozoic time. American Journal of Science, 301, 182-204. Chiodini, G., Fondini, F., Kerrick, D.M. Rogie, J., Parello, F., Peruzzi, L. & Zanzari, A.R., 1999. Quantification of deep CO2 fluxes from central Italy: Examples of carbon balance for regional aquifers and soil degassing, Chemical Geology, 159, 205-222. Chiodini, G., Frontini, F., Cardellini, C., Parello, F. & Peruzzi, L., 2000. Rate of diffuse carbon dioxide Earth degassing estimated from carbon balance of regional aquifers: The case of central Apennine, Italy. Journal of Geophysical Research, 105(B4), 8423-8434. Dando, P.R., Hughes, J.A., Leahy, Y., Niven, S.J., Taylor, L.J. & Smith, C., 1995. Gas venting rates from submarine hydrothermal areas around the island of Milos, Hellenic Volcanic Arc. Continental Shelf Research, 15, 913–929. Daskalopoulou, K., Calabrese, S., Gagliano, A.L., D’Alessandro, W., Submitted. Estimation of the geogenic carbon degassing of Greece. Applied Geochemistry, Submitted. Etiope, G., Ionescu, A., 2015. Low-temperature catalytic CO2 hydrogenation with geological quantities of ruthenium: a possible abiotic CH4 source in chromite-rich serpentinized rocks. Geofluids 15, 438-452. King, C.Y. (1986). Gas Geochemistry Applied to Earthquake Prediction: An Overview. Journal of Geophysical Research, 91, 12,269-12,281. Martelli, M., Nuccio, P.M., Stuart, F.M., Di Liberto, V., Ellam, R.M., 2008. Constraints on mantle source and interactions from He-Sr isotope variation in Italian Plio-Quaternary volcanism. G3, Volume 9, 2. Mörner, N.A., Etiope, G., 2002. Carbon degassing from the lithosphere, Global. Planet. Change, 33, 185–203. Pearce, J.M., Czernichowski-Lauriol, I., Lombardi, S., Brune, S., Nador, A., Baker, J. et al., 2004. A review of natural CO2 accumulations in Europe as analogues for geological sequestration. Geology Society of London Special Pubblication, 233, 29–41 Rizzo, A.L., Caracausi, A., Chavagnac, V., Nomikou, P., Polymenakou, P.N., Mandralakis, M., Kotoulas, G., Magoulas, A., Castillo, A., Lampridou, D., 2016. Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system. Scientific Reports 6:28013. doi: 10.1038/srep28013

ABSTRACT. Non-destructive techniques provide a continuous analysis of sediment cores and constitute an essential tool in the reconstruction of past environmental and climatic conditions. XRF-core scanning in particular can provide a high-resolution record of element intensities, the ratios of which can be used in order to decipher palaeoenvironmental characteristics. One of the main aims of this research, which was carried out within the framework of the ERC-funded DISPERSE project, was the application of the XRF-core scanning technique in order to investigate the palaeoceanographic and palaeoclimatic conditions that prevailed in the southern Red Sea during the late Quaternary. Preliminary results give us a qualitative description of the environmental conditions that prevailed during the sediment deposition in the upper slope and inner shelf of the Farasan Islands, located within the southern Red Sea.

ABSTRACT. The Lesvos Petrified Forest was formed by silicification process of plants during the Lower Miocene era, when intense volcanic activity occurred in that region. It is situated in the western part of Lesvos island (NE Greece) and consists of hundreds of standing and lying fossilized tree trunks, covering an area of 150 km2. It is one of the most important natural heritage monuments in the world and in 2004 the area was included in the Global Geoparks Network. The Natural History Museum of the Lesvos Petrified Forest is the management body of Lesvos Geopark (Zouros, 2010). During the last three decades, a great number of excavations are taking place in the area, revealing important fossil plants and providing crucial palaeobotanical and volcano-sedimentological information. Despite its significance, the conduction of extensive geochemical and mineralogical analyses on fossil plant samples from this area has merely commenced (Pe-Piper et al., 2019), providing information on the permineralization process. The present study aims to shed light on the silicification of the Lesvos fossil woods, by analyzing the silica polymorphs comprising the latter samples. Seventeen fossil plant samples were collected from the Sigri pyroclastic formation within the Lesvos Petrified Forest. Several analytical techniques were employed. A Philips QUANTA 200 Environmental Scanning Electron Microscope (ESEM), coupled with an Oxford INCA Energy 200 Energy Dispersive System (EDS) was used for imaging and chemical analyses. For the Raman spectroscopy, a Thermo Scientific DXR Raman Microscope with a 780 nm laser beam was employed. The power value of the sample irradiation was ranging from 6 mW to 12 mW. The average spectral resolution in the Raman shift range of 100-3000 cm-1 was 5cm-1 (grating 400 lines/mm, spot size 2μm). Cathodoluminescence (CL) spectra were collected on polished slabs, at low vacuum mode without coating, using a Gatan MonoCL3 detector with a PA-3 photomultiplier attached to the SEM. For the X-ray diffraction (XRD), a Phillips PW1710/00 diffractometer was used with a CuKα radiation source, equipped with a graphite monochromator. The XRD patterns were obtained by step scanning from 2º to 64º (2θ in steps of 0.020º; 4 s per step). Block sections (Figure 1) of each sample were used for the ESEM-EDS, SEM-CL and Raman spectroscopy analyses, while a ground to powder portion of the same samples was used for the XRD analysis. SEM imaging and EDS spectra provided a first appraisal of the chemical composition of the samples, focusing on silica-rich zones, which were abundant not only in geode-like structures (Figure 1), but also in white, black and green-coloured parts of the fossil plants. While some textural features were evident by ESEM-EDS, the determination of the exact types of silica polymorphs was managed by employing XRD, Raman spectroscopy and CL-SEM methods. Quartz, opal, cristobalite and tridymite were determined by XRD technique (Figure 2). Opal is a micro to non-crystalline form of hydrated silica with high degree of structural disorder. Cristobalite and tridymite are both more common as components of opal than as individual minerals and may form metastable phases in silica-rich volcanic and sedimentary environments (Pe-Piper et al., 2019).

Figure 1. Polished block section of the TX308 fossil plant sample [left] and characteristic SEM images of the same sample showing different silica-rich zones [middle] and geode-like, Si-rich microstructure (various hues of grey colour) and Fe-rich parts (white colour hues) [right].

Figure 2. XRD pattern of a fossil plant sample, showing the mineral phases of quartz (green bars) and opal (red bars).

Figure 3. Raman spectra of a standard moganite mineral (red) and the moganite mineral phase found in a fossil plant sample (blue) [left] and CL spectra of moganite, opal and a Mn and Ba-rich phase found in another fossil plant sample [right].

Raman spectroscopy confirmed the presence of opal and quartz. Thus, quartz was revealed with its intensive band at 465 cm-1 and the secondary bands at 123, 203 and 497 cm-1, while opal showed a characteristic hump between 200 and 500 cm-1, with distinct, strong peaks at 350, 784 and 1590 cm-1 (Iordanidis et al., 2014). Furthermore, moganite, which is a meta-stable silica polymorph typically intergrown with cryptocrystalline quartz, was also determined by Raman spectroscopy, revealing its characteristic peak at 502 cm-1 and the three other shifts at 464, 206 and 123 cm-1. Figure 3 shows the assignment of moganite mineral phase compared to the Raman spectrum of an original, standard moganite sample, collected from Mogan, Gran Canaria, Spain. The cathodoluminescence (CL) technique was employed as a complementary method to all the aforementioned techniques (ESEM-EDS, XRD, Raman) to investigate the fossil wood samples. Quartz, opal and moganite showed distinctive CL spectra. An intensive peak at 650 nm (aprx. 12000 a.u.) and two lower, broader peaks at 430 and 460 nm are determined for quartz (Aparicio and Bustillo, 2012). Opal revealed a CL spectrum with a broad hump between 300 and 500 nm, showing a rather low intensity (aprx. 3500 a.u.), while moganite presented a characteristic double peak at 440 and 470 nm and another at 650 nm with equal intensity (aprx. 6500 a.u.). Additionally, the CL spectrum of a manganese and barium rich phase with very low luminescence is also shown in Figure 3. In conclusion, the utilization of complementary techniques (ESEM-EDS, Raman, CL-SEM and XRD) provided substantial information for the identification of the silica polymorphs comprising the Lesvos petrified wood samples.

ABSTRACT. A temporal study was performed at Oxygono Bay in the coast of Lavrion utilizing metal profiles in combination with radio-chronological models (Sedimentation Rate - SR estimation based on natural radionuclides) resulting in the identification of three periods of mining activities in the Lavrion area (1860-1900, 1900-1930, 1930-1980), as well as a post-mining period (1980-2014). Geochemical investigation of core sediment revealed a steep increase of As, Zn and Mn content from 35 cm depth till the surface. At the same time, the mineralogy of this segment includes primary ore phases (mainly pyrite and arsenopyrite with minor galena and sphalerite), waste rock clasts, slag fragments, gangue phases (quartz, micas, chlorite, ankerite-siderite, dolomite, barite), secondary phases [smithsonite, mimetite - Pb5(AsO4)3Cl], and W-bearing phases (scheelite - CaWO4, ferberite - FeWO4, and hubnerite - MnWO4). It is reasonable to assume that at some points during the second (1900-1930) and the third period (1930-1980), exploitation of the Plaka intrusion related system, and in particular the skarn type mineralization took place. The primary sulfide ore was mainly exploited by floatation for the extraction of Ag-bearing galena whereas the rest of the material including primary ore phases (arsenopyrite, sphalerite and pyrite), gangue (including carbonates and W-bearing phases), and waste granodiorite (as evident by the presence of natural radionuclide 226Ra) were disposed and are now enriched in the sediment core at depths between 10 and 35 cm.

ABSTRACT. The presence of amorphous matter in industrial minerals and rocks during the quantitative analysis with X-Ray diffraction (XRD) is not always visible and its exact quantification may be difficult. This results to an overestimation of the remaining crystalline phases, because the quantitative analysis is normalized to 100 % for the crystalline phases, thus rendering the analysed sample not representative. Therefore, determination of the amorphous matter is an important task for complete assessment of industrial minerals. In this work we applied Rietveld refinement to determine and quantify the amorphous matter in a series of synthetic samples. The samples were examined on a Bruker D8 Advance Diffractometer equipped with a Lynx Eye strip silicon detector, using Ni-filtered CuKα radiation (35 kV, 35 mA). Data were collected in the range 3–70° 2θ with a step size of 0.02° and counting time 1 s per strip step (total time 63.6 s per step). The XRD traces were analyzed and interpreted with the Diffract Plus software package from Bruker and the Powder Diffraction File (PDF). The quantitative analysis was performed on random powder samples (side loading mounting) emplaced in Al-holders, by the Rietveld method using the BGMN computer code. The code performs quantitative analysis by varying the particle size and preferred orientation parameters. Two series of experiments were performed. The first series included mixtures of synthetic quartz and calcite at 1:1 ratio containing 5, 10, 20, 25, 30, 40, 50 and 80% amorphous material. The second series included natural calcite and quartz at the same ratio and the same proportion of glass. In both experimental series corundum (α-Al2O3) internal standard with particle size <1 μm was added. The main difference between the two series of the experiments was particle size. The synthetic quartz and calcite had comparable particle size as the internal standard, whereas their natural counterparts were considerably coarser, being derived from a quartzite and a coarse grained marble respectively. Consequently they were ground with an agate pestle and mortar. The natural samples were free of impurities, within the accuracy of the XRD method. The aims of the work were to determine the accuracy in the determination of the amorphous matter, to evaluate the influence of particle size in the accuracy of the measurements and to identify the amount of glass at which the presence of the hump at 18-30 °2θ, the criterion to identify amorphous matter, becomes visible. The accuracy of the quantitative determinations depends on the particle size of the minerals present in the mixtures (quartz and calcite) due to the microabsorption effect, and the difference between the particle size of the internal standard and the minerals. In the experiments with synthetic quartz and calcite without glass, the amounts of the minerals determined by quantitative analysis were comparable to the calculated values of the mixtures assuming particle size <1 μm (error ± 1-2%). In the mixtures with natural quartz and calcite similar error values between the experimental and the calculated abundances were observed for particle size <10 μm. In the synthetic samples good agreement between the calculated and the actual content was observed for assuming preferred orientation for calcite. By in contrast, in the natural samples good agreement between the calculated and the actual contents (error ± -2%) was observed for assuming preferred orientation for both minerals. In all cases increasing particle size led to increase of the calcite content and decrease of the quartz and the corundum (internal standard) contents. The mixtures containing glass also showed similar trends in the mixtures of both the synthetic and natural minerals. In the experiments with synthetic quartz and calcite minimum errors were observed in experiments assuming particle size <1 μm, whereas in the experiments with natural quartz and calcite minimum errors were obtained assuming particle size <10 μm. In addition, particle size affects the absolute error of determination of amorphous matter. The relative error in natural samples was higher for amorphous matter contents lower than 20% (Figure 1). As expected, for higher amorphous matter contents the relative error decreased due to decreased uncertainty and it was comparable in the two sets of experiments (Figure 1). The XRD traces of the mixtures of both the synthetic and natural minerals showed the existence of a hump in the range 18-30 °2θ characteristic of the amorphous matter in mixtures containing more than 25% glass. For lower glass contents the hump was hot visible. The only indication for the presence of an additional phase undetected by X-rays was the gradual decrease of the intensities of the diffraction maxima of both calcite and quartz, with increasing amorphous matter content. This indicates that the lack of the hump is not a safe criterion for the recognition amorphous matter at low amorphous matter contents and that the presence of amorphous matter should be verified and quantified by the use of an internal standard. Rietveld refinement is a very promising technique in this aspect. Nevertheless, particle size should be carefully controlled for optimum results. It is suggested that particle size for more accurate determinations of amorphous matter should be lower than 10μm, preferably less than 5μm and that sample preparation should be carefully made to avoid preferred orientation of mineral phases.

ABSTRACT. Introduction The Pleistocene sediments of the Rio-Antirio Βasin (Achaia, Greece) have yielded several terrigenous plant assemblages. In this study, numerous plant fossils as disarticulated parts, mainly leaves and defoliate shoots, have been collected from two fossiliferous sites in the Vigla Sychainon area (Vigla I and IIΙ). Based on recent data from the micropalaeontological analysis of marine sediments found stratigraphically bellow the plant bearing sediments and especially the presence of the coccolithophore Emiliana huxley (Tsoni et al., this volume), a late Middle Pleistocene age can be inferred for the examined plant material. Our main objectives include the description and taxonomic identification of the plant remains, the determination of the palaeoflora and the reconstruction of the regional palaeovegetation. Methods More than 1.500 plant macro-remains, mainly foliage and shoot impressions, were collected by the Paleontology and Stratigraphy laboratory team of the University of Patras. The remains were quite fragmentary and lack organic material preventing cuticular analysis. Initially, the collected material was prepared carefully with thin needles and soft brushes. Afterwards, acrylic resin (Paraloid B72) was used for the conservation of morphological details. The taxonomic determinations and systematic affinities were based mainly on leaf morphology by recording the basic macro-morphological features of the fossils in protocols (e.g. laminar shape, margin type, venation). For the reconstruction of the vegetation, the published data on European plant palaeoassemblages, the autoecology of modern allies and the taphonomical processes that affected the examined material were taken under consideration. Results About 1/3 of the collected plant remains were identified to family or genus level. The great majority of them represents Angiosperm taxa of trees or shrubs [tab. 1, fig. 2]. Fagaceae predominates the assemblage with a deciduous oak which is characterized by lobed leaves (Quercus) [fig. 3]. At least two additional oak species, one of them evergreen, also occur. Ulmaceae is represented by Zelkova and possibly an elm (Ulmus) species [fig. 1]. Moreover, broad-leaved elements such as Platanus, Acer and Populus are identified. Rarely needles of Gymnosperm origin (possibly Pinaceae) are present. Conclusions-Discussion According to the preliminary results from the study of Vigla palaeoflora it can be concluded that: • The plant assemblage is profoundly dominated by a deciduous oak with lobed leaves. • The genus Zelkova it seems to survive through most of the middle Pleistocene in NW Peloponnese while in central Europe it had disappeared much earlier. Today Zelkova is found as a relict species in the Mediterranean area with two endemic species in Crete and Sicily respectively. • The severe fragmentation of the plant remains probably indicates allochthonous fossil deposition (leaf transportation by winds or likely water currents). • The assemblage represents a gallery forest with Platanus, Populus, Ulmus and possibly Zelkova and Quercus that might thrived across an active river channel or a lake. In the lowland surrounding area, a mixed mesophytic forest mostly with deciduous elements such as oaks, maples and Zelkova likely occurs.

Further research is required in order to conclude a final definition of the palaeoflora and the palaeovegetional reconstruction. For a more purposeful systematic affinity of the identified taxa, the future study will focus on their comparison to the modern Mediterranean allies and determination to species level.

ABSTRACT. Coral reefs are hosts of a remarkable variety of animals and plants, ranging from a few hundred species living in the Amazon Reef, to thousands of species living in the Great Barrier Reef. The structures are made mainly from corals and shelter many species that are endangered, while some are endemic to specific niches. The health, abundance and diversity of the organisms that make up a coral reef are directly linked to the surrounding terrestrial and marine environments. For this reason, molluscs are used as bioindicators in reef ecosystems, because they are situated in a variety of ecological niches in hard substrate environments (Zuschin, 2001, Koskeridou et al. 2017). In this study, the community structure of Tortonian coral reef associated molluscs from Central Crete (Greece) is investigated. In Messara basin, near Filippi village (Crete), in proximity to the reef, mollusc fossils were extracted from pebbly sandstone deposits. When evaluating the abundance of mollusc species, we detected a dominance of carnivore gastropods (53% of the species), hosting 34 species belonging to 25 genera. Some examples of carnivore species are included in families like Cassidae which feed on echinoids (Tewfik, 2013), Conidae that feed mainly on polychaete worms (Jiménez-Tenorio et al. 2019) and Muricidae with Naticidae that drill to feed on mollusc shells (Sawyer & Zuschin, 2011). Also, we observed a striking presence of bivalve suspension feeders, for example Megacardita sp., which require relatively high hydrodynamics. Furthermore, herbivore species like Persististrombus sp. and Alvania sp., as well as the spongivore Cerithiopsis sp. were present. Finally, considering the small coral parts and red algae in the deposits, the samples indicate a well oxygenated shallow marine paleoenvironment on a sandy bottom, with sponges, coral patches and seagrasses. Additionally, skeletal parts of fish, as well as echinoid spines were found in sieved material. According to previous published studies, a sirenian fossil has been found in Filippi (Svana et al. 2010), an herbivore sea mammal, similar to those existing today on tropical coral reefs. We also gathered information about other animals living in the ecosystem, without obtaining any body fossils, either because their bodies were not found or they did not have hard parts to be fossilized. The shells form habitats for a series of organisms (Alberti & Reich, 2018). Trace fossils of Entobia and Caulostrepsis are formed from sponges and boring polychaetes, respectively (Alberti & Reich, 2018). Broken and healed shells are indications of crustaceans preying on gastropod shells (Lindström & Peel, 2005, Alberti & Reich, 2018). We are aware that our sampling material is not enough for estimating species richness (Kusworo et al. 2015). Despite of that fact, by taking into account the information on spatial variability and distribution patterns of organisms in modern coral reef environments (Taylor, 1968), we can address our material to a specific ecological niche in this Tortonian coral ecosystem. Using statistical analysis on our quantitative and qualitative results of the fossil fauna, we identified the ecosystem of the coral reef, for the first time in Greece. Our findings point towards a sandy environment between the beach and the reef, with a proximity towards the reef. Trophic relationships, of the organisms living in ecosystems such as the present one, have been recently discussed (Alberti & Reich, 2018). Using a similar model, we can show the trophic food chain of the niche and the complexity of the life in a Tortonian coral reef in the Mediterranean Sea. Further research will compare this material with other Miocene sampling areas, for example the Gatun locality in Panama (Alberti & Reich, 2018), and their paleoenvironmental implications, improving our knowledge about how such ecosystems functioned in the past.

ABSTRACT. Study area The structural grain of Greece is traversed by a 140-km-long system of grabens that includes three members namely the Corinth graben in the east, the Patras graben in the west and the bridging with the Rion graben in the middle (Doutsos et al. 1988). Rio graben is an asymmetric graben with a NE trending Peloponnesian border fault hosting significant offset between the mainland of Greece and NW Peloponnesus (Kontopoulos & Zelilidis 1997). The basin is severely tectonised by a dense fault array comprising WNW normal faults and NE-trending transfer faults (Doutsos et al. 1988). Rio basin is also a region of significant stratigraphical and palaeontological interest. For this reason, several authors have studied sediments from NW Peloponnesus trying to address the geological evolution of the recent past and proposed different ages and palaeoenvironmental interpretations. The study area is located between the villages of Sychena and Velvitsi on the west side of Charadros River and the name of the studied section is Vigla. The purpose of this work is to determine the sedimentary environments and the palaeo-ecological conditions of the studied section and to unravel the Middle - Upper Pleistocene environmental changes. Material and methods Microfaunal analyses were carried out on 121 samples collected every 20-40cm from a natural section in the area of Vigla (east of Sichena village) with a total thickness of about 34 meters. Sediment samples were washed through 500 and 63 μm mesh sieves. When abundant microfaunal elements were present, a combined total of 300 specimens of benthic foraminifera and ostracod tests were collected. Out of the 121 sediment samples, 88 contained sufficient numbers of specimens for quantitative analyses and 33 were barren or contained scarce specimens (<10%). Species and their ecological characteristics were mainly determined based on previous studies of Mediterranean benthic taxa (Cimerman & Langer 1991, Relative volumes of Stereo-atlas of ostracod shells). Species were grouped based on their ecological characteristics and relative abundance diagrams were prepared for each group. Furthermore, 2 smear slides were produced for sediments of marine orgin in order to investigate the presence of calcareous nannofossils. For statistical purposes, the data matrix was standardized to percentages of the entire sample. Four measures of species diversity were calculated: (1) species richness (S), (2) Simpson’s index (1-D), (3) the Shannon–Wiener index [H(s)] and (4) the evenness index, using the PAST3 software (Hammer et al., 2001; version 3.19, 2018). Cluster analysis was run for samples (Q mode) and different outputs of the dendrogram have been compared in order to find the most homogeneous clusters or groups. In addition, correspondence analysis (CA) was also used to correlate taxa and samples. Furthermore, stratigraphic columns were produced. The colors of the depicted layers in the columns were selected based on the Munsell colour system. Sediments were analysed in situ and Munsell colour notations were collected with the use of a Minolta CM-2002 reflectance spectrophotometer. Results In order to check the continuity of the layers we collected samples from three closely spaced well exposed sequences from the same area (Fig. 1). Through the micropalaeontological analysis, four different facies were identified. This allowed us to establish the presence of two normal faults and a disconformity that intercept the sequences. For this reason, in this study, the results are expounded separately for Sequence 1, 2, 3 and 4 (Fig.1). As a general picture, microfossils were abundant in the samples from Sequence 2 and 3, whereas they were scarce or absent in the samples from Sequence 1 and Sequence 4 was barren. • Sequence 1 has a total thickness of 1110 cm and is mainly composed of olive green silts. According to the microfaunal analysis, 4 ostracod taxa have been identified in the studied samples and the total absence of benthic foraminifera is remarkable. Based on the percentage abundance diagrams, statistical analysis and the microfaunal composition of the layers of Sequence 1, six main units (1-6) can be distinguished, 3 of which are barren (Units 2-4-6). The microfauna of this section reflects a primarily brackish environment. • Sequence 2 is mainly composed of gray clays and silts and has a total thickness of 1200 cm. This sequence is rich in micro- and macrofauna as well. According to the microfaunal analysis this section is composed of 28 different taxa of benthic foraminifera and 20 different ostracod taxa. According to the relative abundance diagrams and statistical analysis as well, for this Sequence there is a clear division into two main units, a brackish and a marine unit After calcareous nannofossil analysis from the marine unit’s sediments, Emiliana huxleyi was identified. • Sequence 3 is mainly composed of grey silts nevertheless at the upper part the grain size increases to sand. This sequence has a total thickness of 1855 cm and is rich in micro and macro fauna as well. Based on the microfaunal analysis, 11 different ostracod species and 7 different foraminifera species were identified. Based on the percentage abundance diagrams and the micro-faunal composition of the layers of Sequence 3, three main units that reflect a primarily brackish environment can be distinguished. • Sequence 4 constitutes the last 8 meters of the section. This sequence consists of a massive, mainly matrix supported barren red conglomerate that overlies uncomformably the sediments of Unit 3. Discussion Detailed analyses of benthic foraminifera and ostracoda of a 33.60 meters section have been performed. The employed micropalaeontological analysis and the respective statistical methods that were used, indicate that the microfaunal assemblages of the lower sequence 1 reflect a low salinity lagoon environment. The remaining part of the sequence 1 corresponds to a lagoon with low salinity and freshwater influxes. The microfaunal assemblages of this part of this sequence, reflect the continental-end member of a lagoonal environment. In Sequence 2, the fauna of the lower unit is characteristic of a lagoon with periodic freshwater influxes. The upper part of this section has been characterised as marine. The marine unit can be separated further into two subunits, an open lagoon with good connection to the open sea and a shallow marine environment. In conclusion, the first 4 m of Sequence 2 are indicative of a lagoon ecosystem, but the remaining part of the section is indicative of a closed gulf. At Sequence 3, the main part is indicative of a restricted lagoon with high salinity water influxes that changed gradually to an open lagoon and later again to a closed lagoon. It has been observed that there are repetitive environmental changes from brackish to more or less marine environments, especially between Sequences 2 and 3. The last sequence overlies uncomformably the other three sequences. Sequence 4 is barren of micro or macrofauna and indicates an alluvial fan environment. The palaeonvironmental changes that have been recorded in our study area are the result of eustatism and tectonism as well. Hence, the uplift or subsidence events that took place during the middle and late Pleistocene control the evolution of the palaeoenvironments and the depositional history across the Rio basin. Based on the stratigraphic analysis of the studied section, Vigla presents roughly the same stratigraphic features with Aravonitsa-Location 11 that Palyvos et al. (2010) described. According to them at the base of MNN21a Corinth Gulf was expectedly a lake, isolated from the sea by a sill. The lowest occurrence of E. huxleyi in the Corinth Gulf is expected at the MIS7e highstand, as only then sea water with E. huxleyi had the chance to enter the gulf. The presence of E. huxleyi in Vigla section and its stratigraphic resemblance with Aravonitsa 11, lead us to conclude that this highstand affected both the western part of Corinth Gulf and Rio Basin as well.

ABSTRACT. New insights into the floristic composition, vegetation changes and climate variability over the last 17000 years are provided by the two new high-resolution pollen records from lakes Ohrid and Prespa. The Lake Ohrid (DEEP core) pollen record is the first continuous Late Glacial-Holocene sequence from Lake Ohrid, as existing Late Glacial and Holocene records from Lake Ohrid suffer from discontinuities in sedimentation (Sadori et al., 2016). This centennial resolution pollen record along with an increased resolution in the pollen archive of the adjacent Lake Prespa allow to examine the evolution of local and regional vegetation patterns at an unprecedented scale. Subsequently, we employ the modern analogue technique (MAT) on the new pollen data to reconstruct climate variability in the area over the study interval. Moreover, thirty modern surface (moss) samples collected across an altitudinal transect within the catchments of Ohrid and Prespa were analyzed and integrated in the calibration dataset to improve the local vegetation-climate relationship. In the Last Glacial period (from 17000 cal BP onwards), pollen spectra from both lakes suggest a rather open landscape dominated by steppe elements (mainly Artemisia and Chenopodiaceae) along with grasslands. Pines appear to be the dominant trees in the region during this interval, while relatively high oak percentages suggest their local presence in both catchments. During the Bølling/Allerød deciduous oaks dominate arboreal tree percentages at Ohrid, while at Prespa pines remain dominant throughout this period. During the Bølling/Allerød, deciduous oaks dominate tree percentages at Ohrid, while at Prespa pines remain dominant over this period (Panagiotopoulos et al., 2013). Throughout the Younger Dryas (12900 – 11600 cal BP), the resurgence of steppe elements accompanied by Betula, Ephedra and Hippophae in both pollen records suggest that cold and arid conditions prevailed. Mean annual precipitation values reconstructed applying the MAT method yield values above 400 mm/year during the last 17000 years. These findings imply that moisture availability was most likely not a limiting factor for tree growth and support the refugial character of the region (Panagiotopoulos et al., 2014). The Holocene is characterized by an estimated twofold increase of mean annual precipitation compared to the Younger Dryas. The onset of the Holocene is characterized by the gradual expansion of mixed deciduous woodland dominated by oaks indicating the presence of dense deciduous oak forests in the surroundings of Lakes Ohrid and Prespa. A markedly short-term shift highlighted by an abrupt rise of Artemisia percentages, corresponding to the centennial 8.2 cooling event is registered in the pollen records of both lakes. During the Middle and Late Holocene, the closed forests diversify and percentages of other deciduous taxa such as Acer, Alnus, Carpinus, Fagus, Ostrya increase in both records, especially at Prespa. Although Lake Ohrid is situated a 150 m lower than Lake Prespa at 693 m asl, the presence of Mediterranean elements such as Pistacia and Phillyrea in Ohrid pollen spectra is rather limited compared to Prespa. Intensifying anthropogenic activities during the last two millennia can be inferred in both records from the decline of tree percentages and the coeval increase in pollen of cultivated plants such as walnuts and cereals. These two pollen records from mid-altitudes in southwestern Balkan suggest that the vegetation response in the region is highly sensitive to sub-millennial climate shifts and improve our understanding on plant diversity dynamics, evolution and resilience over the last 17000 years.

ABSTRACT. Planktonic foraminifera are known to alter their shell mass at glacial/interglacials cycles as a function of changing CO2 concentrations in the ocean/atmosphere system. Nevertheless, preliminary results have shown that under similar atmospheric CO2 concentrations planktonic foraminifera alter their mass as a function of latitude (Zarkogiannis et al., 2019b). Our analysis shows that it is ambient seawater density changes that influence calcification and causes observed planktonic foraminifera shell mass increases during glacial times relative to interglacials. The reconstruction of planktonic foraminifera shell volumes from X-ray tomography scans and ambient seawater densities from Mg/Ca and δ18O data showed that a heavier shell would need to be precipitated in glacial climates in order for the increased buoyant force of a denser glacial ocean to be counteracted (Zarkogiannis et al., 2019a). The relationship between shell mass and density allows reconstructions of past ocean stratification and may have implications on the uptake of atmospheric CO2 by the oceans.

ABSTRACT. Thermaikos Gulf is a semi-enclosed, shallow basin in the northwestern part of the Aegean Sea (Fig. 1A). The environmental setting of the area is defined by the three major rivers, two minor ones and several ephemeral streams (Lykousis et al., 2005) that flow into the basin, while the gulf is characterized by eutrophication being one of the most anthropogenically impacted coastal regions of Greece. During the high precipitation period (January-May), the freshwater intrusion can extend southwards enough to seal a major part of the gulf’s surface waters (salinities <25 psu). On the other hand, more saline waters from the northern Aegean Sea flow towards the northeast, entering the inner Thermaikos Gulf (Kontoyannis et al., 2003; Fig. 1B). The aim of this study is to explore changes in the foraminiferal abundance and composition, as compared to a multi-parameter environmental dataset (temperature, salinity, pH and nutrients), magnetic susceptibility and metal content, during a twelve-month monitoring. Sampling of the top 2 cm of the surface sediment was carried out on a monthly basis (December 2015-December 2016) at one station (SP1), and at 5 stations (SP1-SP5) during winter (February 2016) and spring (April 2016), located in Thessaloniki Bay (inner part of the Thermaikos Gulf). Sampling followed the standardized FOBIMO method (Schönfeld et al., 2012), while field measurements at the maximum depth of each station were also conducted. Furthermore, the Foram Stress Index (FSI; Dimiza et al., 2016) was calculated, in order to evaluate the environmental status. Foraminiferal assemblages were dominated mostly by Bulimina spp., Bolivina spp., Uvigerina spp. and various species of agglutinated foraminifera, such as Textularia bocki, Eggereloides scaber, and Leptohalysis scotti. The foraminiferal assemblage also included Ammonia tepida, Haynesina depressula, Nonionella turgida, Lobatula lobatula and miliolids. During late spring-summer (April to August), foraminiferal densities and relative percentages of the living specimens displayed the highest values, while high diversities (Shannon-Wiener index) were observed during winter. The investigated samples for February and April sampling periods were variable with respect to both abiotic parameters and the foraminiferal assemblage, characterized by a mix of stress-tolerant and more sensitive taxa. Samples from the western part of the gulf were characterized by a diverse assemblage that included Bulimina spp., Bolivina spp., agglutinants, miliolids and a variety of small, epiphytic rotaliid taxa. The rest of the gulf presented a monotonous fauna, dominated mostly by stress-tolerant species. FSI values suggested poor/bad to moderate conditions prevailing, while good environmental status has been defined during April at only one station from the western part of the gulf. The variability in foraminiferal composition reflects the exceptional environmental conditions that prevailed in inner Thermaikos Gulf, thus providing further evidence for the species’ seasonality in comparison with the anthropogenic impact. References Dimiza, M.D., Triantaphyllou, M.V., Koukousioura, O., Hallock, P., Simboura, N., Karageorgis, A.P., Papathanasiou, E., 2016. The Foram Stress Index: A new tool for environmental assessment of soft‐bottom environments using benthic foraminifera. A case study from the Saronikos Gulf, Greece, Eastern Mediterranean. Ecological Indicators 60, 611‐621. Kontoyiannis, H., Kourafalou, V.H., Papadopoulos, V., 2003. Seasonal characteristics of the hydrology and circulation in the northwest Aegean Sea (eastern Mediterranean): Observations and modelling. Journal of Geophysical Research 108, No. C9, 3302. Lykousis, V., Karageorgis, A.P., Chronis, G.Th., 2005. Delta progradation and sediment fluxes since the last glacial in the Thermaikos Gulf and the Sporades Basin, NW Aegean Sea, Greece. Marine Geology 222-223, 381-397. Schönfeld, J., Alve, E., Geslin, E., Jorissen, F., Korsun, S., Spezzaferri, S. and Members of the FOBIMO group, 2012. The FOBIMO (FOraminiferal BIo-MOnitoring) initiative-Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies. Marine Micropaleontology 94-95, 1-13.

ABSTRACT. Background The use of non-destructive high-resolution analysis in sediment cores has been continuously increasing through out the years, due to the introduction of new techniques that can attribute to the visualization of different sediment structures, composition etc. Specifically, in paleoclimatic and paleoenvironmental studies, the use of Computed tomography (CT), can provide useful information concerning depositional changes, climatic driven events and short scale depositional changes, that would not be recognized macroscopically. In order to distinguish density changes, complex sedimentary structures as well as grain size in lacustrine and marine sediment cores, the evaluation of the CT imaging has been widely used (Dewanckele et al., 2012; Gualda et al., 2010; Ketcham et al., 2010). Apart from the 3D visualization of a sediment core, one of the most important parameters produced by the CT scanning is the Radiodensity. It is related to the bulk density and chemical composition of the core and has been widely used to describe bulk density (Kenter, 1989), periodic bedding patterns (Boespflug et al., 1995) as well as porosity and permeability (Mena et al., 2015). Objectives Sediment cores characterized by the presence of complex micro structures like varves, are most of the times difficult to be examined by conventional means, so the use of a more high-resolution techniques like CT scanning, seems necessary. The main aim of the present study is to distinguish different sedimentary structures (varve sequences, bioturbation, organic layers) and sedimentological phases, in a 6 m sediment core. Methods For the present study, a 6 m sediment core, retrieved from Vouliagmeni lake in central Greece, was used. The acquiring of the CT images was conducted on General University Hospital of Patras in Greece, using a General Electric lightspeed 16x CT scanner. The acquisition parameters were set as follows: 0.8 gantry rotation time, 16*0.625 mm detector configuration, 8 Images per rotation, Axial thickness 1.25 mm, 120 kV and 175 mA. To enhance the density contrast of the CT acquisitions, the soft tissue and bone kernel were used. For every 1m sediment sequence that was scanned, around 1800 DICOM files were extracted. The raw DICOM files were then processed through the MATLAB based software SedCT v.1.01 (Reilly et al., 2017) and high-resolution Hounsfield Unit (HU) profiles were calculated. Hu values produced are determined by the attenuation of the X-rays, the density of the core and the atomic number. In order to have a better understanding of the additional information provided from the CT scanner, the sediment core was also scanned with a jAi 3CCD RGB line scan camera, with resolution 4096*1px. Profile plots of the RGB colors were created, with the maximum possible resolution, using ImageJ software. Results From the analysis performed at the DICOM files that were extracted from the CT scanning, 4 different lithological facies and two different varve types were recognized (Fig. 1). The laminated sediments that were recognized (Phase A and D), present Hu values ~200 and~ 700 respectively, whereas the silty clay material (Phase C) presents Hu values above 1000 (Fig. 1). Organic rich layers (Phase B) in the core are attributed to HU values 200-400, indicating lower bulk density compared to the other units (Fig. 1). The 3D intensity model that was compiled through the medical software Inobitec DICOM Viewer, provide robust information concerning bioturbation, organic matter and lamination boundaries. Darker areas which correspond to higher density values, attribute to silty clay barren material, whereas the green areas correspond to the CaCO3 rich layers (white layers). Representative images as shown in Figure 1, shows 3 clear laminations with calcite rich material, whereas only one of them can be clearly visible through the line scan camera. Thus, formations that may be disturbed or overlapped in the surface of the core, can now be thoroughly examined. Conclusion Three-dimensional quantitative analysis using X-ray computed tomography combined with line scan digital core images was used for effective core characterization. Internal structure and different sedimentological facies such as (a) organic rich layers, (b) varves and (c) clay rich material were recognized. The applied methodology provide efficient information concerning high resolution sampling strategy avoiding core degradation. The development of new software for the processing of DICOM files and the development of new, more high-resolution CT scanners opens new possibilities in the reconstruction of past environmental changes from lacustrine or marine environments.

ABSTRACT. The Corinth Rift (Greece) is one of the narrowest and fastest extending continental regions worldwide, and has one of the highest seismicity rates in the Euro-Mediterranean region. At its western termination, several active faults are located beneath the city of Patras and the surrounding area, a region of major socio-economic importance for Greece. The Corinth Rift (Greece) is one of the narrowest and fastest extending continental regions worldwide, It is bounded on both sides by active normal faults, on- and off-shore (Moretti et al., 2003; Palyvos et al., 2007) with cumulated offset ~3 km and a series of tilted blocks along the south coast (Doutsos and Poulimenos, 1992; Koukouvelas et al., 1999). It has one of the highest seismicity rates in the Euro-Mediterranean region with, on average, one Mw > 6 earthquake per decade. Recent large earthquakes include Alkyonides 1981 (M = 6.7), Galaxidi 1992 (Mw = 5.8), Aigion 1995 (Mw = 6.1) and Movri 2008 (Mw = 6.4). This last event is located outside of the rift, but is connected to it and is crucial for deciphering the deformation processes at the western termination of the rift and its junction with the Gulf of Patras, where, several active faults are located beneath the city of Patras and the surrounding area, a region of major socio-economic importance for Greece. Previous geodetic studies conducted, which were based on GPS observations observations, revealed North – South extension rates across the gulf of up to about 1.5 cm/yr [Clarke et al., 1997; Briole et al., 2000; Avallone et al., 2004] during the last 20 years. The Corinth Rift Laboratory (CRL) institution (http://crlab.eu) is based on the joint efforts of various European institutions to study fault mechanics and related hazards in the study area. It is included in Geohazards Natural Laboratories of the GEO Supersites and will be one of the Near Fault Observatories (NFO) of European Plate Observing System (EPOS). Displacement rates for the period 2002-2010 obtained from ascending and descending ASAR/ENVISAT multi-temporal interferometry are combined with Global Positioning System measurements from permanent and campaign stations to produce a map of vertical and east-west ground velocities. More specifically initial datasets derived from Persistent Scatterers and Small baselines Subsets techniques. These datasets has been doubled by performing a second running with different initial parameters. Combination of ascending and descending tracks has been used to calculate the east-west and vertical deformation components rates. The wealth of information provided by the availability of eight measurements per original pixel and the combination of several original pixels, allows tracking efficiently the unwrapping errors. Finally improved vertical and east-west velocities were calculated by using an averaging filter and a cutoff threshold based on r.m.s. scattering. In the city of Patras and through the gulf of Patras, the northern continuation of the 2008 Movri earthquake fault (Serpetsid;aki et al., 2014) is connected to the oblique transform zone of Rio. The Rio-Patras fault is off-shore, in front of downtown Patras and penetrates inland between Patras and Rio. Then it rotates progressively and connects with the Psathopyrgos normal fault at the entrance to the Corinth rift. To model the GPS and InSAR velocities, we assume a fault system locked in part of the crust and slowly slipping elsewhere. The deformation shape of the Rio-Patras fault indicates a shallow locking depth and suggests slow slipping below that depth. The large gradient of strike-slip velocities between the south and the north coast at both ends of the Rio-Antirio bridge support a model of deformation accumulation in a very narrow locked layer in the crust, with the rest being unlocked, and therefore not associated with strong seismicity (at least in the last decades until present).

References: M Avallone, A., Briole, P., Agatza-Balodimou, A. M., Billiris, H., Charade, O., Mitsakaki, C. A., et al. (2004). Analysis of eleven years of deformation measured by GPS in the Corinth Rift Laboratory area. Comptes Rendus Geoscience. https://doi.org/10.1016/j.crte.2003.12.007. [Journal Article] Briole, P., Rigo, A., Lyon-Caen, H., Ruegg, J.C., Papazissi, K., Mitsataki, C., et al. (2000). Active deformation of the Corinth rift, Greece: Results from repeated Global Positioning System surveys between 1990 and 1995. Journal of Geophysical Research, 105(B11), 25,605-25,625. https://doi.org/10.1029/2000JB900148. [Journal Article] Clarke, P., Davies, R., England, P., Parsons, B., Billiris, H., Paradissis, D., et al. (1997). Geodetic estimate of seismic hazard in the Gulf of Korinthos. Geophysical Research Letters, 24(11). https://doi.org/10.1029/97GL01042. [Journal Article] Doutsos T., & Poulimenos G. (1992). Geometry and kinematics of active faults and their seismotectonic significance in the western Corinth - Patras Rift (Greece). Journal of Structural Geology, 14(6), 689-699. https://doi.org/10.1016/0191-8141(92)90126-H Koukouvelas, I., Asimakopoulos, M., & Doutsos T. (1999). Fractal characteristics of active normal faults: an example of the eastern Gulf of Corinth, Greece. Tectonophysics, 308(1-2), 263-274. https://doi.org/10.1016/S0040-1951(99)00087-6. [Journal Article] Moretti, I., Sakellariou, D., Lykousis, V., & Micarelli L. (2003). The Gulf of Corinth: an active half graben? Journal of Geodynamics, 36(1-2), 323-340. https://doi.org/10.1016/S0264-3707(03)00053-X. [Journal Article] Palyvos, N., Pantosti, D., Stamatopoulos, L., & De Martini, P. M. (2007). Geomorphological reconnaissance of the Psathopyrgos and Rion-Patras fault zones (Achaia, NW Peloponnesus). Bulletin of the Geological Society of Greece, 40, 1586-1598. [Journal Article] Serpetsidaki, A., Elias, P., Ilieva, M., Bernard, P., Briole, P., Deschamps, A., et al. (2014). New Constraints from Seismology and Geodesy on the Mw=6.4 2008 Movri (Greece) Earthquake. Evidence for a Growing Strike Slip Fault System. Geophysical Journal International, 198(3), 1373-1386. https://doi.org/10.1093/gji/ggu212. [Journal Article].

ABSTRACT. The Corinth Rift (central Greece) is one of the most seismically active areas in Europe due to rapid continental extension that reaches the rate of ~15mm/year in its western part. In contrast to the eastern part, the western part of the rift presents intense microseismic activity and frequent earthquake swarms that have been associated with pore-fluid pressure diffusion at depth (Bourouis & Cornet, 2009). Such an earthquake swarm occurred on 2001 in the SW margin of the rift, in the area of Agios Ioannis, near the city of Aigion. The swarm initiated on 2001 March 28 with a sudden increase in the regional seismicity rate and involved more than 2900 events over a period of 100 days. The largest event of the swarm occurred on 2001 April 8, 10 days after the initiation of the swarm, with the moderate size of Mw4.3. The spatial distribution of the swarm and the focal mechanism of the largest event indicated the activation of a SW–NE fault plane dipping at ∼40◦ to the north-west, which coincides with the unexposed Kerinitis fault (Pacchiani & Lyon-Caen, 2010). The spatiotemporal evolution of the swarm indicated the spatial migration of activity towards the surface with time. This migration pattern is consistent with a pore-fluid pressure diffusion mechanism, where the initial pore-fluid pressure perturbation occurred at some point near the early events of the swarm and progressively migrated at negative pressure gradients towards the surface along the active fault structures. According to the Mohr-Coulomb failure criterion, increased pore-fluid pressure can reduce the effective normal stress along a fault zone triggering earthquakes. Here we investigate the diffusion properties of the Agios Ioannis earthquake swarm and the applicability of such mechanism in triggering the earthquake activity. We consider a probabilistic approach and a stochastic framework that generates the key properties of earthquake diffusion. Within this context, a well-established stochastic framework for modelling anomalous diffusion phenomena in complex heterogeneous media, where linear diffusion equations and Fick’s second law might no longer be applicable, is the continuous-time random walk (CTRW) model (Berkowitz et al., 2006). Within the CTRW context, we consider earthquake occurrence as a point-process in time and space and we map earthquake diffusion with a joint probability density function of spatial jumps and waiting times between successive earthquakes. The analysis of the swarm within this context indicates a broad probability density of waiting times with asymptotic power-law behavior, as well as the power-law growth of the mean square displacement of seismicity with time, with a diffusion exponent well below unity that marks normal diffusion (Fig.1). Such properties are intrinsic characteristics of anomalous diffusion and indicate the slow propagation of seismicity according to a sub-diffusive process. In addition, we combine the CTRW model with fractional kinetics and the time-fractional diffusion equation to provide an analytic description of the spatial migration of seismicity with time. According to the results for various time periods, the derived stochastic model can successfully predict the main features of anomalous earthquake diffusion, indicating a peak of earthquake concentration close to the origin and a stretched exponential decay for the concentration of distant events. Our results are consistent with pore-fluid pressure diffusion as the triggering mechanism of the earthquake swarm. In this case, our results can be understood as a ‘non- Fickian’ relaxation of an initial pore-fluid pressure perturbation that reduces the effective normal stress along the active fault structure triggering the seismicity. The results further indicate that the CTRW model and the fractional diffusion equation can efficiently be used to model anomalous earthquake diffusion in the highly heterogeneous crust.

ABSTRACT. The Western Gulf of Corinth (WGoC) is the most active rift in Europe, having hosted a large number of destructive earthquakes (Makropoulos et al., 2012), as well as multiple swarms (Kapetanidis et al., 2015). It comprises of fault systems striking approximately WNW-ESE, while the focal mechanisms in the area are almost exclusively normal in nature. This complicated structure characterizes the rift as a semi-graben, with the southern coasts of Northern Peloponnesus being uplifted (Armijo et al., 1996). The intense seismic activity in the area has led to significant interest from researchers worldwide. Seismic anisotropy refers to the wave velocity dependence from changes in the polarization direction. A widely studied branch of the above phenomenon is Shear-wave Splitting (SwS), which refers to velocity variations in shear-waves. Upon entering an anisotropic medium, shear-waves undergo splitting and two components of polarization can be distinguished; (a) the one propagating faster (Sfast) and (b) the one lagging behind (Sslow). SwS is quantified by determining two parameters, i.e. the polarization direction of the Sfast (φ) and the time-delay between the arrivals of the two split shear-waves (td). SwS is a featured phenomenon in areas where the crust is permeated by vertical fluid-filled microcracks. According to the Anisotropic Poro-Elasticity (APE) model (Crampin and Zatsepin, 1997; Zatsepin and Crampin, 1997), stress variations in a given rock volume and changes in the characteristics of the fluids affect the geometry of the microcracks. This affects SwS by altering both φ and td. Microcracks are usually controlled by the maximum horizontal compressive stress component (σΗmax). However, local structures can also have an effect on microcracks, leading to spatial differences in the distribution of φ (Li and Peng, 2017). In the WGoC, splitting has been previously studied, exhibiting polarization directions mostly aligned to σΗmax, i.e. WNW-ESE (e.g. Giannopoulos et al., 2015; Kaviris et al., 2017, 2018). However, deviations from this orientation have yet to be fully explored. The current study aims to clarify whether these outliers can be attributed to anisotropy controlled by structural factors. The development and operation of dense seismological networks in the WGoC have a significant impact in the above, permitting the continuous recording of events by broadband seismological stations all around the rift. The Hellenic Unified Seismological Network (HUSN) is a joint venture of the operators of seismological networks in Greece and has been active since 2008, covering a significant portion of the gulf. The Corinth Rift Laboratory Network (CRLN) is the result of the partnership between Greek and French institutes with its main focus being the study of seismicity within the gulf. Data by both networks are used in the presented work. The large dataset of event-station pairs was analyzed automatically. Initial locations of foci (acquired from the Seismological Laboratory of the National and Kapodistrian University of Athens) were used to determine candidate rays for analysis, i.e. ones with a maximum angle of incidence equal to 45°, in order to avoid converted and scattered phases. Then, two techniques were employed for the SwS analysis, through the Pytheas software (Spingos, 2019). The Eigenvalue (EV) method (Silver and Chan, 1991) utilizes a grid search approach, searching for the pair of φ and td that best minimizes the smallest eigenvalue λ2 of the covariance matrix between the (corrected for anisotropy) horizontal components. To implement this, a signal window for analysis must be provided. Commonly, this is specified by the analyst. However, to fully automate the selection and accommodate a large number of recordings, the Pytheas software has followed a Cluster Analysis (CA) approach (Teanby et al., 2004). Measurements with the EV method are repeatedly conducted for a range of candidate signal windows around the S-wave arrival. The outer bounds of the windows’ range are defined by the S-P times and the period of the shear-waves. Thus, a population of measurements with coordinates (φ, td) is acquired, where clusters are formed, indicating stable solutions. A hierarchical agglomerative clustering is initially performed to determine the clusters. The optimal one is selected, based on the degree of constraint. The selected signal window is the one corresponding to the measurement with the smallest uncertainties, included in the most constrained cluster. Results from this analysis were then used to obtain the spatial variation of φ, with the use of the TESSA program (Johnson et al., 2011). For a selected grid, the average of the polarization direction is calculated for each cell, by taking into account the φ value attributed to each passing ray and weighting their contribution according to td. Results of the above analysis indicate that shear-wave splitting in the WGoC is mostly influenced by stress. While this was evident for the coastal areas (due to the stations being located on land), the spatial distribution of φ confirms this for the offshore region within the rift. However, the area surrounding the Mornos delta, to the NW, offers a different perspective, with polarization directions oriented NE-SW, perpendicular to σΗmax. While this could be interpreted as the microcracks reaching a critical state, where their aspect-ratio is inverted due to increased fluid pressure causing φ to flip by 90°, the time-independent nature of this change offers refuting evidence to the hypothesis. We attribute this difference in direction to local structures in the broader Mornos delta area, where both topographical and tectonic data indicate NE-SW trending structures. Distinguishing between the factors influencing SwS is a decisive step in seeking relations between fluid-related processes, such as diffusion/migration and splitting, enabling the latter to function as a monitoring tool.

ABSTRACT. An Mw6.8 earthquake occurred on 25 October 2018, 30 km offshore of the west-southwest coastlines of Zakynthos Island. The aftershock sequence being still in progress, appeared very productive with 6 aftershocks of M>5.0 in the first month and tens of M>4.0 ones. Centroid moment tensor solutions (https://www.globalcmt.org/CMTsearch.html) for the main shock are predominantly indicative of thrust faulting in response to northeast – southwest compression, with a very low angle plane (dip=24o) for a significant dextral strike slip component (rake=165o), alike for the the largest aftershock (Mw5.9, dip=7o, rake=169o) that occurred five days afterwards. The affected area occupies the northwesternmost part of the Hellenic Arc – Trench System is characterized by remarkably high seismic activity, with frequent strong (M>6.0) earthquakes that have caused severe casualties and damage during the last six centuries since historical information is available. The recurrence of these shocks is rather in the order of few decades, given that in the vicinity of the main rupture, an Mw=6.6. occurred in 1997. The 2018 Zakynthos earthquake and accompanying activated secondary faults suggest strong distributed crustal deformation in the area, highlighting the need for better understanding of active faulting and seismic hazard in this region. Aftershock Location and Evolution of the Sequence The Hellenic Arc–Trench System was recognized as a subduction zone with the oceanic plate of eastern Mediterranean being subducted under the Aegean microplate and constitutes the most prominent seismotectonic feature of the broader Aegean region. The seismicity is well delineated along the subduction front with the stronger events exhibiting thrust faulting along NW–SE striking faults and NE–SW striking axis of the maximum compression, placed perpendicular to this front in the study area. West – Northwest of the Zakynthos Island the Kefalonia Transform Fault Zone (KTFZ), with dextral strike slip motion, connects the oceanic subduction with the continental collision between the Outer Hellenides and the Adriatic microplate. This dextral strike–slip faulting was recognized as a major discontinuity between the Apulian platform and the western Hellenic Arc and was firstly suggested by Scordilis et al. (1985). The properties of the activated structure were investigated with accurate relocated data and the available fault plane solutions of some of the stronger events. Station delays were calculated for further refining the locations of the aftershocks provided by the catalogs of Geophysics Department of the Aristotle University of Thessaloniki (GD–AUTh), following a procedure described in Karakostas et al. (2014) and the HYPOINVERSE (Klein, 2002) computer program. The double–difference location technique along with a cross – correlation algorithm was employed for further refining the locations, revealing a seismogenic layer extending from 3 to 15 km depth, whereas all the aftershock locations do not obviously align with the strike or dip of the mainshock focal mechanism; however, location uncertainties are expected in this region, with the depth control of the smaller events to be difficult constrained. Figure 1 shows the relocated aftershock spatial distribution where different magnitude ranges are depicted with different symbols and the main shock epicenter by the star. The activity is spreading offshore the southwestern Zakynthos coastline, and persistently in an area activated since the first hours of the emergence of this seismic excitation, which is remarkably continuing with frequent M3.0 and M4.0 aftershocks for almost six months. The general trend of the relocated seismicity shows a strike agreeing well with the northwest–striking plane from the moment tensor solutions. The location refinement contributes in documenting kinematic details of the seismicity in relation to the active structures, whereas the inclusion of smaller magnitude earthquakes in the relocated data set provide the means for a more detailed analysis of the spatiotemporal evolution of the sequence. Both the distribution of seismicity and fault plane solutions show that thrusting with strike slip motion are both present in low angle fault segments. The segmentation of the activated structure could be attributed to the faulting complexity combining the regional compressive tectonics with the dextral strike slip motion, mainly manifested along the KTFZ. Investigation of the spatial and temporal behavior of seismicity revealed possible triggering of adjacent fault segments that may fail individually thus preventing coalescence in a large main rupture. Multiple activation of secondary faults is observed, since the activity is extended over 60 km, an area well above from what is expected from known scaling laws expressing the fault length and rupture area as a function of the main shock magnitude. This implies that strain energy was not solely released on a main fault only, but on secondary and adjacent fault segments as well. The as much as possible reliable definition of their geometry forms the basis for the structural interpretation of the local fault network.

Figure 1. The 2018 Zakynthos relocated aftershock sequence in the first three months after the main shock occurrence, along with the focal mechanisms of the main shock and its largest aftershock shown as equal area lower hemisphere projections.

Summary The 2018 Mw6.8 Zakynthos earthquake and its largest aftershock were crustal thrust – faulting events. The stress axes orientations are consistent with the regional stress field and with the focal mechanisms of past regional events (Papadimitriou, 1993). Complex earthquake sequences are common in the study area, where multiple adjacent and conjugate faults are contemporaneously activated. The abundance of aftershock activity appears to be correlated with structural complexity, in the sense that aftershock populations reflect fault populations surrounding major faults. Acknowledgements The plots were made using the Generic Mapping Tools version 5.4.4 (Wessel et al., 2013). Support is acknowledged by “HELPOS – Hellenic System for Lithosphere Monitoring” (MIS 5002697) project, implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). References Karakostas, V.G., Papadimitriou, Ε.Ε., Gospodinov, D., 2014. Modeling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities, Geophysical Journal International 197, 525–541, doi: 10.1093/gji/ggt523. Klein, F.W., 2000. User’s Guide to HYPOINVERSE–2000, a Fortran program to solve earthquake locations and magnitudes, U. S. Geological Survey Open File Report 02–171 Version 1.0. Papadimitriou, E.E., 1993. Focal mechanism along the convex side of the Hellenic Arc and its tectonic significance. Bolletino di Geofisica Teorica ed. Applicata 35, 401–426. Permanent Regional Seismological Network operated by the Aristotle University of Thessaloniki, doi:10.7914/SN/HT. Scordilis, E.M., Karakaisis, G.F., Karakostas, B.G., Panagiotopoulos, D.G., Comninakis, P.E., Papazachos, B.C., 1985. Evidence for transform faulting in the Ionian Sea: The Cephalonia Island earthquake sequence. Pure Applied Geophysics 123, 388–397. Wessel P., Smith W.H.F., Scharroo R., Luis J.F., Wobbe F., 2013. Generic Mapping Tools: Improved version released. EOS Trans AGU, 94, 409–410.

ABSTRACT. The geodynamic regime in western Greece manifested by intense seismic activity results from the convergence between the African and Eurasian lithospheric plates (e.g. Armijo et al., 1992), while the westward motion of the Turkish plate imposes an important contribution (e.g., Armijo et al., 1996). The region hosts both continental collision to the north and oceanic slab subduction to the south; these features are connected by the right-lateral Cephalonia Transform Fault (CTF). Active tectonics involves all types of faulting. Reverse and strike-slip faulting characterize the interplate type of deformation (Papadimitriou et al., 2006; 2012; Kassaras et al., 2016), while normal and strike-slip faulting prevails in intraplate regions (Kassaras et al., 2014a, 2014b), forming pull-apart basins (King et al., 1993) and the rapidly spreading Corinth Rift (Kapetanidis & Papadimitriou, 2011; Kapetanidis et al., 2015). GPS measurements demonstrate rapid deformation to the south (~35 mmyr-1) and a slower one of the order 5–8 mmyr-1 in NW Greece (Chousianitis et al., 2015). Deformation across the area of Western Greece is mainly accommodated within the accretionary sediments comprising the external Paxi, Gavrovo and Ionian geotectonic units, escarped from the African margin and colliding against the un-deformed Eurasian hinterland (e.g. Royden and Papanikolaou, 2011). Zakynthos Island is located at the front of the present-day Hellenic Trench, which is formed along the convergent zone of the plate boundaries between the subducting oceanic lithosphere of Tethys and the overriding Eurasian plate. The high level of seismic activity in the area is the result of the intense crustal deformation in the Central Ionian Sea, which leads to the occurrence of moderate to strong events. The most recent events include the November 18th, 1997 (Mw=6.5) earthquake, SW of Zakynthos Island, the December 2nd, 2002 (Mw= 5.5) earthquake, a sequence of earthquakes on October 2005 (Mw=5.6) and April 2006 (Mw=5.5–5.7) south of Zakynthos, the June 8th, 2008 (Mw= 6.4) Andravida earthquake, the January 26th, 2014 (Mw= 6.1) Paliki earthquake and the November 17th, 2016 (Mw= 6.4) Lefkas earthquake. A strong earthquake of moment magnitude Mw=6.8 occurred on 25 October 2018, ~50 km to the SW of Zakynthos Island, causing some damage in the municipality of Zakynthos and on the islands of Strofades. This event was one of the largest that have occurred in the vicinity of Zakynthos Island since 1983. It was strongly felt in Western Greece but also in other parts of the Greek mainland. More than 4,000 aftershocks were located in the framework of this study. The aftershock zone covers a region about 60-70 km long in a N110E direction and ~80 km towards N20E. In this work we attempt to highlight the nature and dynamics of the earthquake sequence, the driving forces that acted during its evolution and potential consequences of its occurrence on the regional hazard. To this aim, a comprehensive dataset of recordings from the Hellenic Unified Seismological Network (HUSN) and the Hellenic Strong Motion Network (HSMN; Theodulidis et al. 2004) was compiled and the following tasks were carried out: (a) determination of precise hypocentral locations employing a custom velocity model, followed by double-difference relocation, (b) spatiotemporal analysis of the sequence, (c) regional moment tensor inversion for the determination of the source parameters of the mainshock and the larger events, (d) inversion of focal mechanisms to investigate the local stress-field distribution and (e) computation of Coulomb stress transfer to identify regions and receiver faults that were loaded with additional stress. After the manual determination of P- and S-wave phase arrivals, a dataset of 900 best located earthquakes, between 26 October and 30 November 2018, was compiled and a local velocity model was obtained using a travel-time residual and location errors minimization method (e.g. Kissling et al., 1994). Locations were recalculated with the new model and relocated with the use of a double-difference algorithm. The spatial distribution of epicenters revealed several distinct clusters, some of which are in general agreement with the geometry of known mapped faults and compatible with the strike of Quaternary faults. Regional moment tensor inversion revealed a focal mechanism with a strike of N16E, a dip of 25 and a rake of 166. Most of the determined focal mechanisms of the sequence followed this trend. Nevertheless, the largest aftershock displayed strike-slip characteristics. In addition, focal mechanisms, including events of past activity (Kassaras et al., 2016), were inverted to determine the regional stress field (Hardebeck and Michael, 2006). A complex stress field in the broader area of Central Ionian Sea, related to both thrust and strike-slip faulting was revealed.

Acknowledgements We acknowledge support of this study by the project “HELPOS – Hellenic Plate Observing System” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

References Armijo, R., Lyon-Caen, H., Papanastassiou, D., 1992. East-west extension and Holocene normal-fault scarps in the Hellenic arc. Geology 20, 491–494. Armijo, R., Meyer, B., King, G.C.P., Rigo, A., Papanastassiou, D., 1996. Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean. Geophys. J. Int. 126, 11–53. Chousianitis, K., Ganas, A., Evangelidis, C.P., 2015. Strain and rotation rate patterns of mainland Greece from continuous GPS data and comparison between seismic and geodetic moment release. J. Geophys. Res. Solid Earth 120, 3909–3931. Hardebeck, J.L. and Michael, A.J., 2006. Damped regional-scale stress inversions: Methodology and examples for southern California and the Coalinga aftershock sequence. J. Geophys. Res. Solid Earth, 111, B11310. Kapetanidis, V., Papadimitriou, P., 2011. Estimation of arrival-times in intense seismic sequences using a Master-Events methodology based on waveform similarity. Geophys. J. Int. 187, 889–917. Kapetanidis, V., Deschamps, A., Papadimitriou, P., Matrullo, E., Karakonstantis, A., Bozionelos, G., Kaviris, G., Serpetsidaki, A., Lyon-Caen, H., Voulgaris, N., Bernard, P., Sokos, E., Makropoulos, K., 2015. The 2013 earthquake swarm in Helike, Greece: seismic activity at the root of old normal faults. Geophys. J. Int. 202, 2044–2073. Kassaras, I., Kapetanidis, V., Karakonstantis, A., Kaviris, G., Papadimitriou, P., Voulgaris, N., Makropoulos, K., Popandopoulos, G., Moshou, A., 2014a. The April-June 2007 Trichonis Lake earthquake swarm (W. Greece): New implications toward the causative fault zone. J. Geodyn. 73, 60–80. Kassaras, I., Kapetanidis, V., Karakonstantis, A., Kouskouna, V., Ganas, A., Chouliaras, G., Drakatos, G., Moshou, A., Mitropoulou, V., Argyrakis, P., Lekkas, E., Makropoulos, K., 2014b. Constraints on the dynamics and spatio-temporal evolution of the 2011 Oichalia seismic swarm (SW Peloponnesus, Greece). Tectonophysics 614, 100–127. Kassaras, I., Kapetanidis, V. and Karakonstantis, A., 2016. On the spatial distribution of seismicity and the 3D tectonic stress field in western Greece. Phys. Chem. Earth, Parts A/B/C, 95, 50–72. King, G., Sturdy, D., Whitney, J., 1993. The landscape geometry and active tectonics of northwest Greece. Geol. Soc. Am. Bull. 105, 137–161. Kissling, E. et al., 1994. Initial reference models in local earthquake tomography. J. Geophys. Res. 99: 19635-19646. Papadimitriou, P., G. Kaviris and K. Makropoulos, 2006. The Mw=6.3 2003 Lefkada Earthquake (Greece) and induced transfer changes. Tectonophysics, 423, 73-82. Papadimitriou, P., Chousianitis, K., Agalos, A., Moshou, A., Lagios, E. and Makropoulos, K., 2012. The spatially extended 2006 April Zakynthos (Ionian Islands, Greece) seismic sequence and evidence for stress transfer. Geophysical Journal International, 190 (2), 1025-1040. Royden, L.H., Papanikolaou, D.J., 2011. Slab segmentation and late Cenozoic disruption of the Hellenic arc. Geochemistry, Geophys. Geosystems 12(3). Theodulidis N. et al., 2004. HEAD1.0 : A unified accelerogram database”, Seism. Research. Lett, 75, 41-50.

ABSTRACT. Spatiotemporal analysis of the early 2019 seismic excitation offshore north Lefkada Island V. Karakostas1, E. Papadimitriou1, T. Kostoglou1, O. Mangira1, P. Bountzis1 (1) Geophysics Department, School of Geology, Aristotle University of Thessaloniki, GR54124 Thessaloniki, Greece, vkarak@geo.auth.gr

A moderate magnitude Mw5.4, earthquake occurred on the 5th of February 2019 in the offshore area north of Lefkada Island, strongly felt in the Lefkada city and the onshore continental area to the east, with no major damage or injuries reported. The main shock was followed by a very productive aftershock sequence with more than 400 recorded, and about 370 of them being relocated, by the 15 March 2019. An Mw4.2 earthquake has occurred on the 15th of January 2019, to the northeast of the 05/02/2019 event, also followed by several aftershocks. The affected area has been frequently visited by moderate earthquakes in the last decades with no one of them exceeding in magnitude M6.0. The activated area is located at the boundary between the Kefalonia Transform Fault Zone (KTFZ) to the south and the Adriatic – Eurasian Collision to the north. The continental collision is expressed by a belt of thrust faulting with a NE – SW direction of the axis of maximum compression, runs along the eastern coastline of Adriatic Sea and terminates just north of Lefkada Island. The KTFZ is a major dextral strike slip fault zone that accommodates frequent strong earthquakes, clustered in space and time probably due to the stress transfer between the fault segments comprised in the fault system (Papadimitriou, 2002). The northernmost fault segment of KTFZ was activated in 2003 with an Mw6.2 main shock and a rich aftershock sequence, the accurate location of which provided for the first time the indication that the major fault segments bound the western coastlines and the contemporaneously activated secondary ones lie onshore (Karakostas et al., 2004). The investigation of this activity is challenging to shed light in the seismogenic setting and the complex geodynamics of the area, prerequisite for any seismic hazard assessment study. Its location is critical to decipher how these secondary structures play a role in accommodating strain at the borderline of the KTFZ, an area where also reverse focal mechanisms were determined for moderate earthquakes that occurred in the last few decades. Seismicity relocation and spatial characteristics Seismicity was relocated after manually picking the P and S arrivals and using the 1–D velocity model along with a recalculated vp/vs ratio suggested by Papadimitriou et al. (2017) for the relocation of the 2015 Lefkada aftershock sequence. Station delays were calculated for further refining the locations, following a procedure described in Karakostas et al. (2014) and the HYPOINVERSE (Klein, 2002) computer program. The relocated seismicity allowed refined and more reliable picture than the disperse epicentral distribution derived from the regional catalogue, revealing seismicity concentrations mainly close to the stronger earthquakes’ epicentres (Figure 1). The total earthquake set includes ~370 events that could be detected by an adequate number of seismological stations and relocated. The first strong Mw4.2 earthquake triggered the activity in the northern cluster, with a comparatively noticeable aftershock frequency and magnitudes, with 15 aftershocks in the first 24 hours and additional 20 in the next five days. It is noteworthy that the activity continued and even intensified at this location after the Mw5.4 main shock. The close distance of the two concentrations could be investigated through interaction of small – magnitude earthquakes within the sequence. The February aftershocks delineate an ~10 km long zone, which seems larger than expected from known scaling laws connecting rupture length with earthquake magnitude. Given that the locations are highly accurate, it implies that several secondary fault segments were activated in a cascade mode through stress transfer firstly due to the main shock coseismic slip and in the following among the activated fault patches. Independently of the moderate main shock magnitude this seismic sequence appeared remarkably productive with an Mw4.2 aftershock, a handful of M>3.0 aftershocks and numerous smaller magnitude events (shown with different symbol size and colour, according to their magnitude). The sequence behaves as a foreshock – mainshock – aftershock – like sequence, with a 3 located foreshocks in the five days preceding the main shock occurrence and about 163 events occurred in the first five days, an interval taken the same in length for comparison reasons, the 72 of them being occurred in the first 24 hours. The fault plane solutions of all the three stronger earthquakes, which are depicted in Figure 1 as lower hemisphere equal area projections, exhibit strike slip motion either dextral on an almost N–S striking fault plane, or sinistral on an E–W conjugate one. Although the N–S fault strike and the dextral motion is compatible with KTFZ geodynamic properties, motion on the conjugate faults cannot be ruled out and further investigation is stimulating.

Figure 1. Relocated seismicity in the study area along with the fault plane solutions of the 3 stronger earthquakes shown as equal area lower hemisphere projections.

Summary The as much as possible accurately relocated intense activity that observed in the first few weeks of the year (2019) beyond the northern termination of the KTFZ, forms distinctive clusters, the most prominent of which is associated with the 05/05/2019 Mw5.4 earthquake. The spatial distribution and the fault plane solutions of the three (3) stronger events evidence the prevalence of strike slip motion in this area, as a continuation of the KTFZ to the north of Lefkada Island. The complexity of the active structures, which in addition to the primary segments of the KTFZ are capable of producing disastrous earthquakes, highlights the need for intensive maintenance and careful analysis of the seismicity. Acknowledgements The financial support by the European Union and Greece (Partnership Agreement for the Development Framework 2014 -2020) under the Regional Operational Programme Ionian Islands 2014-2020, for the project “Telemachus – Innovative Operational Seismic Risk Management System in the Region of Ionian Islands” is gratefully acknowledged. References Karakostas, V.G., Papadimitriou, E.E., Papazachos, C.B., 2004. Properties of the 2003 Lefkada, Ionian Islands, Greece, earthquake seismic sequence and seismicity triggering. Bulletin Seismological Society America 94, 1976–1981. Karakostas, V.G., Papadimitriou, Ε.Ε., Gospodinov, D., 2014. Modeling the 2013 North Aegean (Greece) seismic sequence: geometrical and frictional constraints, and aftershock probabilities, Geophysical Journal International 197, 525–541, doi: 10.1093/gji/ggt523. Klein, F.W., 2000. User’s Guide to HYPOINVERSE–2000, a Fortran program to solve earthquake locations and magnitudes, U. S. Geological Survey Open File Report 02–171 Version 1.0. Papadimitriou, E.E., 2002. Mode of strong earthquake occurrence in central Ionian Islands (Greece). Possible triggering due to Coulomb stress changes generated by the occurrence of previous strong shocks. Bulletin Seismological Society America 94, 3293–3308. Papadimitriou, E., Karakostas, V., Mesimeri, M., Chouliaras, G., Kourouklas, Ch., 2017. The Mw6.7 17 November 2015 Lefkada (Greece) earthquake: structural interpretation by means of aftershock analysis. Pure & Applied Geophysics, DOI 10.1007/s00024–07–1601–3.

ABSTRACT. Two circular permanent lakes of 150 and 250m diameter and 6-8m depth to an unconsolidated muddy bottom occur 250 m apart from each other, isolated in the agricultural fields SW of the town of Almyros (Thessaly, central Greece). Geological outcrops that exhibit possible underground structures are missing in the area. The age of the lakes is assumed to be Late Pliocene to Early Holocene with a minimum age of approx. 7000 years BP. Gravity and magnetic measurements that conducted in this area seems to support the idea that these structures are compatible with a meteorite impact hypothesis of a projectile, which may has split into two fragments before reaching the earths surface.

ABSTRACT. It is well-known that low body-wave velocities (Papazachos and Nolet, 1997) and quality factor (high attenuation) (Ventouzi et al., 2014) have been observed beneath the Southern Aegean volcanic arc, at the depth of ∼60–90 km. This is usually attributed to the subduction process of the Eastern Mediterranean lithosphere under the Aegean microplate, resulting in the partial melting above the subducting slab. As a result, P and S waves from intermediate-depth earthquakes are strongly attenuated along the South Aegean Sea volcanic arc. On the other hand, P and S waves from in-slab events, propagating toward the outer Hellenic arc, exhibit relatively high-frequency amplifications (Figure 1). More recently, Ventouzi et al. (2018) confirmed the existence of the high attenuation mantle wedge beneath the volcanic arc by calculating a new 3D attenuation (QP and QS¬) model. This 3D-model has been determined by the tomographic inversion of the linear decay of acceleration spectra at high frequencies, tS*, calculated for body waves and assuming an ω2 earthquake source model. The main target of this study is to compare the new 3D anelastic attenuation model for the upper mantle of the southern Aegean Sea subduction area (Ventouzi et al., 2018) with the Ground Motion Prediction Equations, GMPEs (Skarlatoudis et al., 2013) and to employ this model into the stochastic simulation approach developed by Kkallas et al. (2018a, b), in order to generate realistic seismic waveforms for intermediate depth events occurring in the southern Aegean subduction area. For this purpose, we initially used a synthetic dataset of intermediate-depth events recorded by the same seismological stations later used in the stochastic simulation and calculated the theoretically expected QS values based on the 3D anelastic attenuation model of Ventouzi et al. (2018). The results were compared with the corresponding anelastic attenuation coefficient values of the GMPE from Skarlatoudis et al. (2013), showing a good agreement. In order to predict several expected ground motion measures, for example peak ground acceleration (PGA) and peak ground velocity (PGV) as a function of distance and magnitude, we used the results obtained from the stochastic simulation approach. These simulations were performed with the EXSIM code (Motazedian and Atkinson, 2005), as adapted by Boore (2009), taking into account finite-fault effects for ground-motion modelling. The main concept is based on the summation of the contributions to ground motion over all of the sub-sources comprising the fault at the observation site, considering proper delays of sub-sources due to rupture propagation. Several researchers have investigated the seismotectonic setting, strong ground motion attenuation and source properties that control seismic motions for the intermediate-depth earthquakes of the south Aegean Sea (e.g. Boore et al., 2009; Skarlatoudis et al., 2009, 2013; Kkallas et al., 2013, 2018a, b). These studies provide constraints on several source and propagation path parameters for this class of events, namely the stress parameter, expected fault dimensions, quality factor of the Aegean mantle, geometrical spreading etc. In the present study, these results have been incorporated in order to perform a realistic stochastic finite-fault modelling of intermediate depth earthquakes in the South Aegean Sea. To confirm the stability and effectiveness of the employed 3D attenuation model, we model the PGA and PGV distribution of three intermediate depth earthquakes of the southern Aegean Sea subduction zone, namely the 2011 intermediate-depth earthquake (M 6.1, h~75 km), the 2004 M = 5.5 event (southeast of Astypalaia), and the more recent 2015 M = 5.0 Nisyros intermediate earthquake (h~130km), which all exhibit spatially anomalous seismic motion and macroseismic (damage) patterns. In general, there is a good agreement between peak ground-motion measures (PGA/PGV) and synthetic values for the entire dataset. Finally, the approach allowed us to explore simulation for future, larger magnitude events in the study area. A typical application example of the proposed methodology was considered for the scenario of a Mw=7.5 intermediate-depth event which will occurr near the islands of Kos and Nisyros (eastern Hellenic arc). The obtained results are promising, confirming the significant differences of fore-arc and back-arc damage distributions, suggesting that the role of intermediate-depth earthquakes should be further explored using the updated 3D attenuation model.

ABSTRACT. Introduction Taking into consideration the major damage caused by the disastrous earthquake of 7th September 1999 (5.9R), the need for further and deeper investigation of the geological structure of the subsurface came up. The damage distribution of an earthquake is usually related to the tectonic structures of the area (Dilalos and Alexopoulos, 2017). Unfortunately, since the areas are covered with artificial surfaces, such as buildings, industrial infrastructures, roads, bridges and generally artificial surfaces, the geological research is quite complicated. The missing geological information for the deep subsurface can only be retrieved using geophysical methods. Given the fact that the 54.5% of Athens basin is covered with artificial surfaces (Dilalos, 2018), not all the geophysical methods can be applied. The land gravity measurements seem like the most applicable method for such a deep geotectonic investigation. Geological regime In Figure 1, a simplified geology map of the area (Dilalos, 2018) is provided, mostly based on the geotectonic study by Papanikolaou D. et al., (2002). The autochthonous Metamorphic Unit is compiled mainly of dolomites, marbles and shales. On the other hand, the “Ypopelagoniki” unit consists of Triassic-Jurassic limestones and some base clastic formations from Paleozoic. The Athens Unit (upper allochthonous unit) is comprised of two main parts, the upper one which is basically limestones and the lower one, called “Athens Schists” which is basically a geological mélange that consists of sandstones, shales, phyllites, limestones and marls. The “Alepovouni”, located tectonically between the autochthonous metamorphic unit and the “Athens” unit, consists of limestones (upper part) and additionally schists and phyllites in the base, because of its low metamorphism. The post-alpine geological formations cover the biggest part of the basin. More than ten different post-alpine, Quaternary and Neogene geological formations had been proposed by Papanikolaou D. et al., (2002), but here they are observed simplified in groups that will help the gravity survey, based on Dilalos (2018). Establishment of gravity bases and data acquisition Taking into account the traffic jam of this over-populated metropolis and the increasing time that we would spend moving among the stations and the base re-measurements, we planned and established very cautiously the gravity base network, distributing spatially fourteen (14) gravity bases (Fig. 1-blue squares). The entire gravity base network is referred to the IGSN’71 datum (Morelli et al., 1974) as it was tied with repeated measurements (ABABA type) to an already established gravity base in the University of Athens (Hipkin et al., 1988). Due to the complicated geology of the area and the urban environment, the gravity measurements were planned on a grid, with a station grid spacing set to 1km. Afterwards, some stations were added among the first ones, in order to clarify the status of some ambiguous areas. The gravity database is comprised of 1122 gravity stations (Fig. 1), acquired with the LaCoste & Romberg G-496 gravity meter. The essential coordinates of the gravity stations and bases were determined with high precision, using a Differential Global Positioning System (dGPS) and the static technique. Results and Conclusion A geologically constrained 3D gravity modelling was produced (Fig. 2) using the “VOXI” Earth modelling module, based on the Complete Bouguer Anomaly calculated after the standard data reduction and the application of the innovative Building Correction (Dilalos et al., 2018). The subsurface was discretized in a 3D block mesh, where all blocks have a cell size equal to 1000m for X-Y and 500m for Z direction. The produced block mesh (Fig. 2) is constituted by a total of 12760 blocks of individual density contrast. The density contrast ranges from -0.32 gr/cm3 (bluish colors) to 0.669 gr/cm3 (reddish colors), with a maximum depth of almost 6800m. The evaluation of this density model, given the fact of the geological formations’ densities (Dilalos, 2018) provide valuable information for the subsurface geological structure of Athens basin. It verifies the existence of faults mapped as possible but also indicates the location of possible new ones. Acknowledgements The fieldwork was partially supported by the NKUA-SARG (contract no. 70/4/9254). The authors would like to thank Ms. Achtypi S., Ms. Kaplanidi H., Mr. Mavroulis S., Mr. Michelioudakis D.and Ms. Drosopoulou E. for their contribution during the field measurements. We would also like to gratitude Mr. Stylianos Chailas for the kind supply of the established gravity base data.

ABSTRACT. The recent development of nanotechnology and its use in consumer products leads to the emission of manufactured nanomaterials into the environment. Exposure of humans and living organisms to these materials in the environment may in some cases pose a risk for human health and the ecosystem. For that reason, it is imperative to determine the presence and characteristics of these materials in relevant environments. On the other hand, naturally occurring mineral particles are very common in nature, ranging in size from a few nanometers to hundreds of micrometers. A typical example is particles that result from the precipitation of substances entering the seawater, from hydrothermal vents, or other volcanic activity. The presence of such mineral particles in natural systems has been frequently documented, but quantitative measurements of their numbers and characteristics are scarce. To date, the distinction between manufactured and naturally occurring nanomaterials has not been achieved. Here, we present a new detection strategy, based on the Faradaic charge transfer when NPs impact an electrode.The direct detection of particle collisions at electrodes is a recent field and presents several competitive advantages over the state-of-the-art methods. It is characterized by high sensitivity, high frequency of measurements, high selectivity, ability to measure non-opaque samples and has the potential to be developed into a portable device for conducting immediate, spatially resolved measurements. In this technique, a microelectrode is kept under suitable electrochemical control and is introduced into a suspension containing nanoparticles. When a nanoparticle arrives at the electrode due to Brownian motion, electron tunneling between the particle and the electrode occurs. Upon contact and depending on the applied potential, an electrochemical reaction is triggered: the nanoparticle can be electrochemically reduced or oxidized, or can mediate (catalyze) a charge transfer processes giving a transient current that appears as a “spike” or a “step” in the chronoamperometric scan. These electrochemical signals are interpreted thus having results for NPs properties.

ABSTRACT. The present study focuses on metal (As, Cd, Cr, Cu, Ni, Pb, Sb, Zn) enrichment along the Karvounoskala stream, which is located near Stratoni village and discharges in Ierissos Gulf. The wider area has a long history concerning the mining activities of Greece (Chalkidiki Peninsula). Geologically, the study area belongs to the Kerdylia formation, part of the Serbomacedonian massif. In this region, the Stratoni granodiorite intrudes marbles, biotite- and hornblende-biotite-gneisses and amphibolites which are overlain by alluvial deposits. Nine samples were in total collected downstream Karvounoskala stream as follows: 5 soils and 4 sediments. After they were transferred at the laboratory, the samples were dried at 50˚C for 48h in order to remove the moisture. Total soil and sediment samples were used for the chemical analyses, after they were pulverized in a mortar to achieve a homogeneous sample with particle sizes <0.063mm. Total metal concentrations were determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and compared to the global average composition of shales (Turekian et al., 1961). Metal enrichment was assessed by using the following geochemical indices: enrichment factor (EF), contamination factor (Cf), geo-accumulation index (Igeo) and contamination degree (Cd). According to the results of this study, metal concentrations in soils followed the order Pb >Zn > As > Cu > Cr > Sb > Ni > Cd. Regarding the sediment samples, their metal content presented minor differentiation by the soils following the order Zn > Pb > As > Cu > Cr > Sb > Ni > Cd. In general, soil and sediment compositions appear rather uniform. This is expected, since both of them derive from the weathering of the rocks in the study area. The studied metals derive from the weathering of the surrounding geological formations, as well as from the metal occurrences that they host. All samples are partly enriched in Sb, Pb, As, Cd and Zn due to the presence of polymetallic sulfides, Fe-Mn oxides and slags in the soils and sediments. Traces of Cr and Ni are attributed to amphibolite occurrences.

ABSTRACT. The accumulation of heavy metals Mn, Pb, Zn, Cu, Cd, and As in the soil-wheat and soil-corn systems of the western Drama plain agricultural land was studied. Results showed that soil were contaminated by heavy metals coming from the dispersion of Mn mine wastes. The concentration of Cd in wheat grains and the concentration of Pb in corn grains were found locally to exceed maximum permissible limits for foods. This may create health risk to habitants via the consumption of these crop grains.

ABSTRACT. According to the European groundwater directive (2006/118/EC), groundwater bodies must be protected from qualitative and quantitative degradation. According to the 1st revision of the National Water Management Plan for the River Basin District of Attica, the groundwater body of Loutraki is characterized by a good qualitative and quantitative status. The water demand (mainly for drinking purposes) of Loutraki is covered exclusively by the alluvial aquifer located at the southern part of the basin. It is estimated that the annual groundwater abstractions from the alluvial aquifer are approximately 2.5 million m3. During the summer, the groundwater abstractions are doubled as Loutraki is a popular touristic resort and this causes an additional pressure on the aquifer. Within such a framework, the scope of the present study is to assess the variation of groundwater level between the wet and dry season as well as to compare the present and the past piezometric level for the studied part of the aquifer by using Geographical Information Systems. Several researchers have used GIS techniques for the assessment of groundwater-level fluctuation (Tiwari et al, 2017). Loutraki basin is located at the southeast part of Korinthiakos Gulf in the Northeast Peloponnese (Fig. 1) and covers an area of approximately 53.3 km2. The maximum elevation in the basin is 1368 m a.s.l. while the mean elevation is 470 m a.s.l. The climate is temperate with a dry summers and rainy winters and a mean annual temperature of 18.2 οC. The alluvial aquifer covers an area of 7.45 km2 with a maximum water level depth of 150 m (Kounis and Vitoriou-Georgouli, 2003). The delineation of the groundwater body of Loutraki is depicted in Fig. 1. The thickness of the unsaturated zone increases gradually from the western to the eastern part of the aquifer and ranges from zero to 125 m while the maximum thickness of the saturated zone is approximately 200 m. Hydraulic conductivity ranges from 2×10-4 to 5.2×10-5 m/s and the transmissivity from 1.6×10-2 to 4.3×10-3 m2/s (Stamatis and Voudouris, 2000). The present study assembles new data (2017) and existing unpublished data (2009) which were acquired by the Municipal Directorate for Water and Sewage of Loutraki – Agioi Theodoroi on groundwater level/piezometric head of the alluvial aquifer. The groundwater level depth in 14 boreholes was recorded during the wet season in April 2017 and the dry season in September 2017 (Fig. 1). The delimitation of the study area was performed based on the geographical distribution of the boreholes and it is estimated at 6.4 km2 (Fig. 2) covering only a small part (12%) of the basin. The borehole depths range from 20 to 220 meters with a gradual depth increase towards the north-eastern part of the alluvial aquifer. Four piezometric maps were produced using ESRI’s ArcGIS 10.4 software by using the Spatial Analyst toolbox and Inverse Distance Weight (IDW) interpolation technique. IDW was selected as opposed to Kriging interpolation due to the imbalanced spatial distribution of the measurement points across the study area. Also, the root mean squared error (RMSE) indicator by IDW was lower in comparison to the difference between observed and calculated values. The aquifer is under unconfined conditions in the upstream part transforming in confined conditions in the coastal part. Groundwater recharge occurs through infiltration of rainfall and torrents. Limited recharge originates from the upstream boundary of the aquifer via fractured rocks. Groundwater flow has a direction of northeast to southwest and the piezometric head ranges from higher than 12.73 m to below sea level (<-0.48 m) (Fig. 2). A seasonal variation of the piezometric head between wet and dry seasons of both 2009 and 2017 is noted by comparing the maps. During the dry season (Fig. 2a, c), the piezometric head decreases reaching negative values near the coastal zone at the southwest part of the basin. This is attributed to increased groundwater abstractions during the summer months. No significant variations were observed between the wet and dry seasons of 2009 and 2017. This indicates that the quantitative status of the aquifer remained relatively stable within the 8-years period. However, it must be highlighted that the risk of sea water intrusion in the coastal zone is high during the dry season. This is also proved by the fact that electrical conductivity and chloride concentrations increase near the coastal zone (Pyrgaki et al., 2016). Therefore, water managers must take measures in order to avoid aquifer overpumping during summer months in order to minimize the risk of sea water intrusion in the coastal part of the aquifer system.

Acknowledgements The authors would like to thank the Director of the Municipal Directorate for Water and Sewage of Loutraki – Agioi Theodoroi Mr. Anastasios Mastrantonakis as well as its technical staff for providing access to the Municipal boreholes and their help during water level measurements as well as for providing existing groundwater level data.

References Kounis, D., Vitoriou-Georgouli, A. (2003). Hydrogeological survey regarding the hydrological balance of the metallic aquifer of Loutraki area. Institute of Geology and Mineral Exploration (IGME). Unpublished Technical Report, Athens (in Greek). Pyrgaki, K., Argyraki, A., Kelepertzis, E., Paraskevopoulou, V., Botsou, F., Dassenakis, E., Skourtsos, E. (2016). Occurrence of hexavalent chromium in the ophiolite related aquifers of Loutraki and Schinos areas. Bulletin of the Geological Society of Greece 50, 2261-2270. Stamatis, G., Voudouris, K. (2000). Delineation of protection zones according to hydrogeological criteria: the case study of Loutraki alluvial aquifer. Digital Library of Theophrastus, Mineral Wealth Journal 116, 13-36 (in Greek). Tiwari, A. K., Nota, N., Marchionatti, F., & De Maio, M. (2017). Groundwater-level risk assessment by using statistical and geographic information system (GIS) techniques: a case study in the Aosta Valley region, Italy. Geomatics, Natural Hazards and Risk 8(2), 1396-1406.

ABSTRACT. The Oropos Basin was one of the most important lignite-bearing areas in Greece. The lignite deposits in the area of Mavrosouvala, between Markopoulo and Milesi, has been known since 1830 and mining activity in the area lasted for about a century. Numerous waste lignite and spoil heaps have been neglected ever since. Previous research in the area has underlined geogenic contamination of potentially toxic elements in the groundwater and the Neogene sediments bedrock of this basin (Stamatis et al. 2011; Kampouroglou and Economou-Eliopoulos 2016, Kampouroglou et al. 2017). However the environmental impact of the neglected lignite wastes has not been evaluated so far. The aim of this research was to sample mining wastes from different disposal sites and perform mineralogical and geochemical analysis. Characterization of samples includes semi-quantitative mineralogical analysis by SEM/EDS analysis and XRD, bulk waste geochemical analysis for major and trace elements by XRF and ICP-MS and LECO methods. Based on field observations and the bulk analysis the mine waste material is characterized as highly heterogeneous consisting of variable amounts of waste lignite, soil and waste rock. Total sulfur concentration (LECO measurements) in the all the waste types including the waste rock is high i.e. from 3.5 up to 10.7 wt.% associated with a high pyrite content (Fig. 1). Organic carbon also shows high variability from 0.1 to 19 wt.%. According to SEM/EDS analysis the sulfides (pyrite, sphalerite) and montmorillonite host significant amounts of Arsenic in the waste lignite whereas goethite is the main carrier of Arsenic in the waste rock (dolomitic limestone). Ashing of lignite waste and then dissolution by nitric acid in closed vessels (and microwave heating) was performed in order to minimize loss of volatile elements during the open vessel acid attack at high temperatures. Trace element concentration of the digests were measured by ICP-MS. The total Fe concentration in the lignite waste (XRF analysis) ranges from 5.1 to 7.9 wt.% being probably associated with the abundance of pyrite; it is also possible to participate in clay minerals (montmorillonite). The average concentration of As, Cr, Co, Ni in the lignite ash is higher than the respective ash concentration of the main Greek lignite deposits (Table 1). The determination of As in the ash samples is considered accurate, since the digestion test was performed in closed vessels (Lachas et al. 1999).

Figure 1. Pyrite occurrence as framboids in the lignite waste (a-d) and Arsenic-pyrite in the dolomitic limestone host rock (e-f)

Table 1. Concentrations in ppm of trace elements and iron of lignite waste (bulk analysis by XRF) and lignite ash (ICP-MS analysis) from Oropos basin. For comparisons lignite ash from the main lignite deposits of Greece are shown (Foscolos et al. 1989, 1998) Element Oropos Lignite waste (dried bulk, n=3) Oropos Lignite ash Ptolemaida/Amyntaio ash Megalopoli ash Drama ash Fe (wt.%) 5.1 – 7.9 4.3 As 80 – 119 168 23.5 – 104 20 – 30 102 – 606 Ba 74 – 544 612 – 852 487 – 700 425 – 1323 Cd 2 – 7 2 <3.3 <1.8 <2.1 Cr 610 – 640 535 234 – 591 236 – 351 50 – 290 Co 102 – 216 132 18 – 35 25 – 53 9 – 25 Cu 56 – 98 50 140 – 220 165 – 194 25 – 110 Mo <15 18 – 29 10 – 33 46 – 712 Mn 195 – 576 185 304 – 1172 319 – 531 168 - 1273 Ni 643 – 2752 1842 229 – 651 215 – 226 57 – 246 Pb 14.7 – 40 20 50 – 67 56 – 66 50 – 119 U 15 – 40 21 – 97 12 – 13 33 – 313 V 188 – 344 219 267 – 348 227 – 282 116 – 737 Y 21 – 41 24 – 26 35 – 47 28 – 298 Zn 116 – 194 83 57 – 98 110 – 185 50 – 242

High concentration of Cr and Ni ranging from 234 to 591 ppm and 229 and 651 ppm, respectively have also been recorded in the ash from Ptolemaida – Amyntaio lignite basin (Papanikolaou et al. 2004). The paste pH test (1 part solid: 1 part water) was used to determine the acidic nature of the waste samples and ranged from 2.7 to 4.9. Samples having a paste pH of < 4.0 are considered potentially acid forming (PAF) and these samples contain significant acidic sulfate salts. Preliminary results of acid-base accounting tests (ABA) showed Nutralization Potential Ratio (NPR) values < 1and Net Nutralization Potential (NNP) < -20 kg CaCO3/t indicating potential acid generation from the mine waste material. These conditions could enhance metal leachability and cause an increased risk for the local water and soil.

Acknowledgements We would like to thank V. Skounakis from the Department of Geology and Geonvironment, NKUA for performing the SEM/EDS analysis. References Alexakis, D., Gamvroula, D., 2014. Arsenic, Chromium, and Other Potentially Toxic Elements in the Rocks and Sediments of Oropos Kalamos Basin, Attica, Greece. Foscolos, A.E., Goodarzi, F., Koukouzas, C.N., Hatziyannis, G., 1989. Reconnaissance study of mineral matter and trace elements in Greek lignites. Chem. Geol. 76, 107-130. Foscolos, A.E., Goodarzi, F., Koukouzas, C.N., Hatziyannis, G., 1998. Assessment of environment impact of coal exploration and exploitation in the Drama basin, Northeastern Greek – Macedonia. Energy Sources 20, 795-820. Kampouroglou, E., Economou-Eliopoulos, M., 2016. Assessment of the environmental impact by As and heavy metals in lacustrine travertine limestone and soil in Attica, Greece: Mapping of potentially contaminated sites. CATENA, 137-166. Kampouroglou, E., H. Tsikos, and M. Economou-Eliopoulos., 2017. Carbonate stable isotope constraints on sources of arsenic contamination in Neogene tufas and travertines of Attica, Greece. Open Geosci. 9:577–592. Lachas, H., Richaud, R., Jarvis, K.E., Herod, A.A., Dugwell, D.R., Kandiyoti, R., 1999. Determination of 17 trace elements in coal and ash reference materials by ICP-MS applied to milligram sample sizes. The Analyst 124, 177–184. Papanicolaou, C., Kotis, T., Foscolos, A., Goodarzi, F., 2004a. Coals of Greece: a review of properties, uses and future perspectives. Intern. J. of Coal Geol. 58:147-169 Stamatis, G., Alexakis, D., Gamvroula, D., Migiros, G., 2011. Groundwater quality assessment in Oropos-Kalamos basin, Attica, Greece,” Environmental Earth Sciences, vol. 64, no. 4, pp. 973–988.

ABSTRACT. Integrate various evidential maps that obtained from spatial data set of great scientific significance and has considerable value for mineral prospectivity mapping (MPM). Mineral prospectivity mapping by considering the various aspect of data set layers and information can be used to make mineral exploration less expensive, more efficient, and more accurate, it is important to move beyond traditional concepts and establish a rapid, efficient, and intelligent method of predicting the existence and location of minerals. Over the past years, two contrasting analytical approaches have been used to produced mineral prospectivity mapping. one is a conceptual knowledge-driven approach, and the other is an empirical data-driven approach. The knowledge-driven approach in exploration is carried out by extracting the spatial factors from exploration dataset on the basis of the exploration model, quantification of spatial factors and finally integration of these factors through map combination processes. In this study the integration process includes the weighting and scoring of different layers affecting the copper mineralization at studied area (Khorasan Razavi province SE of central Iran structural-metamorphic zone.) carried out by Index Overlay method as one of the knowledge- driven approaches within GIS environment. According to obtained results, we could achieve an initial guideline for effectively prospecting copper mineralization in the studied area

ABSTRACT. Geographic Information Systems (GIS) is an upcoming digital technology, which provides the opportunity to share geospatial data globally. This key feature, makes it essential for the communication between the (geo)scientific world and the general audience. Story Maps are an innovative communication technique developed in 2012 by ESRI©, able to achieve a breakthrough on this field. They are interactive maps that combine multimedia content and text that can be displayed on various screen sizes. Individuals have constantly wanted to include geographic information into their lives for things as locating discoveries or registering property (Sui and Goodchild, 2001). GIS Story Maps combine geospatial data with photos, video, audio, and text to visualize a theme or sequential events. Therefore, a Story Map contributes to spatial organization of GIS data in a reading-pleasant way, while it is widely available in a cloud-based software platform (ArcGIS Online) accessible by anyone, beyond institutions, on the World Wide Web (Scott et. al., 2016). Thus, it is a tool for public engagement as it can effortlessly be shared via social media or embedded within a website. One of the objectives of the ERANETMED CrITERIA project, is to provide a dialogue platform for public or private water managers and local communities of areas where the groundwater resources are impacted by hexavalent Cr, mainly as a result of the geological setting. Such areas in central-eastern Mediterranean region and Oman are included as case studies in the project. The ultimate aim is to guide water stakeholders towards a sustainable way of water usage by taking into account water pressures as well as climate change (Pyrgaki et al., 2018). Extended water sampling and analysis have been implemented in the study areas on a seasonal basis and have provided a rich dataset with respect to water quality data. These have subsequently been interpreted in conjunction with the European Union water standards as well as other factors including precipitation and land use. Within this context a Story Map is being developed in order to accommodate the produced data in a comprehensive way and present them in a memorable and compelling character that combines analytical and artistic characteristics. The creation of the Story Map involved selection of a template appropriate for the end recipients and an interesting, memorable and comprehensive title. Then, a proper basemap had to be chosen, in which various layers can be added depending on what is analyzed. Specifically, a global terrain map has been selected and information layers concerning geology, sampling points, boreholes, urban/industrial/rural areas have been added. Symbols on the map are explained either on a legend or in text. Also, multiple graphs, additional maps and other data have been adjusted on the story, such as in the form of carefully designed custom pop ups. These included Piper diagrams with explanation of water type and links to geology, climate concerning charts, elemental concentration ratios, and historical statistics whenever available. Furthermore, hyperlinks for videos, websites and email addresses have been added to provide all necessary information to concerned stakeholders. All of the above, aim to provide helpful information to the local stakeholders and water managers. Story Maps act as a valuable tool, able to bring people closer to the GIS technology and its capabilities, more to draw their attention on a specific issue like the water administration and awaken them from vital issues’ unawareness.

ABSTRACT. Developing a geochemical baseline database through systematic sampling and chemical analysis is a key area of applied geochemistry; it is essential to define the geochemical baselines for the near-surface geological media in order to assess the current state of the environment and to provide information on mineral resources. For this purpose, in the last three decades, many low-to-high density geochemical surveys were conducted at the one-time Geological Survey of Hungary (currently known as the Mining and Geological Survey of Hungary). Until recently, the large amount of geochemical data produced by these surveys was dispersed throughout published literature and maps, but has not been collected and collectively interpreted. Our mission was to develop a geochemical database and to implement revision and interpretation of these archive data. The database currently contains data of more than 30 surveys, including the National Survey, the regional surveys of mountains, data of two pan-European projects (FOREGS and GEMAS) and many large-scale local programs.

ABSTRACT. Arsenic is an element that can cause toxicity even at low concentrations jeopardizing human and animal health [1]. Assessment of pedo-environmental factors that affect the geochemical behavior of As, especially mobility and bioavailability of the element, provides substantial information that may be applied for the restoration of contaminated soils using phytoremediation techniques. Among factors regulating As uptake by plants is the concentration of phosphates in soils since P and As oxyanions show similar geochemical behavior [2]. According to relevant literature, the As hyperaccumulator plant Pteris vittata, can accumulate from some hundred up to some thousand mg of As per kg of dry weight, depending on soil properties and experimental conditions [3]. No study however, systematically questioned the optimum As:P molar ratio in soils in relation to the ability of P. vittata to accumulate As under field conditions. In the present work batch experiments were conducted aiming to: (a) comparatively evaluate As mobilization in two highly contaminated mine soils following the application of phosphates either in the form of a commercial triple superphosphate fertilizer (TSP) or in the form of NH4H2PO4, (b) study As desorption behavior in the two soils and (c) estimate a TSP agronomic dose that can safely enhance As removal from the soils in case of phyto-remediation scenario.

ABSTRACT. Introduction

Given the fact that by 2050 more than 80% of the European population will be living in cities, the quality of the urban environment is becoming an important issue in the 21st century. Since the industrial revolution, with a peak after the Second World War, the urban environment has been contaminated with many inorganic toxic elements and organic compounds, which are being emitted by a wide variety of human activities (industry, traffic, domestic heating, coal and oil combustion, incineration, construction activities, etc.), and often accumulate in urban soil (Johnson et al., 2011).

Although the negative long-term health related hazard of certain elements, such as Pb, has been known since ancient Hellenic times, little or no precautions were taken to protect the workers and the environment. Industries were, and often still are haphazardly distributed within the urban layout. Since, the 1970s a conscious attempt is being made in many countries to develop industrial facilities outside the residential, commercial, and recreational parts of cities. Within the urban structure remain, however, the brownfield sites, and the problems associated with the need of their remediation and redevelopment in order to reduce the pressure on greenfield sites.

Since many health-related problems are linked to the state of the urban environment (Fig. 1a), European citizens want to be aware of the geochemistry of the land their houses are built on. Moreover, it is especially important that the chemical quality of soil in public places, such as schoolyards, parks, playgrounds, kindergartens, recreation areas, and workplaces is known. Estate agents need to know the quality of the land they are marketing, and insurance brokers the potential risks to their customers.

With the frequent occurrence of highly contaminated soil in urban areas, a conscious management of soil excavation, transport, and redistribution within a city is another important issue. Urban soil is generally contaminated to a variable degree, depending on its location relative to a pollution source. Knowledge about soil contamination, geochemical background concentrations, and detailed spatial element distribution is thus becoming a key issue in urban planning. Hence, the increasing interest to map the current chemical state of topsoil (Fig. 1b), and house dust (Fig. 1c) and to define potential risks to human health (Fig. 1d). This knowledge helps to complete still missing comparable geochemical data sets about urban ecosystems. Additionally, such information is urgently needed by decision-makers, local and regional authorities, planners, house buyers, and town administrations, for finding innovative and practical solutions for sustainable urban development and securing human health at a satisfactory level of risk. In fact, multidisciplinary cooperation takes on a completely new dimension in the tackling of urban problems, caused by contaminating activities, i.e., applied geochemists work alongside public health officers, urban planners, medical doctors, etc. Hence, the need for the production of a harmonised urban geochemical database of high quality and integrity for multipurpose use (Figs. 1b, c, d).

Urban geochemistry projects of the EuroGeoSurveys Geochemistry Expert Group The Geological Surveys of Europe have the task of providing high quality geochemical databases for the management of the environment and mineral resources. They have also a long-standing history in urban geochemical surveys, hence the publication of a textbook ‘Mapping the Chemical Environment of Urban Areas’ (Johnson et al., 2011) by members of the EuroGeoSurveys Geochemistry Expert Group. The Group has also published several urban geochemistry case studies in a form of topical publication (Demetriades et al., 2018). Although the results of urban geochemistry surveys, carried out in different European countries, are of good quality, they are, however, incompatible, because of different sampling, sample preparation and analytical methods. In order to produce comparable urban geochemistry data across Europe, a harmonised methodology must be followed. For this purpose, an urban geochemistry manual was written and published in 2015 (Demetriades and Birke, 2015a), and two large bulks of reference samples prepared at the Geoanalytical Laboratories of the State Geological Institute of Slovak Republic. Due to wide interest in the quality of the urban environment, another comprehensive manual was written and published in 2015 (Demetriades and Birke, 2015b), following a request by the European Commission COST Action (TU1206) project ‘SUB-URBAN – ‘A European network to improve understanding and use of the ground beneath our cities’. This manual describes the procedure of (i) sampling topsoil, subsoil, house dust, attic dust, road dust or sediment, atmospheric particulates and bio-indicators, including human tissues, (ii) sample preparation, (iii) laboratory analysis, (iv) quality control, (v) data conditioning, and (vi) data processing and map plotting.

EuroGeoSurveys recognising the importance of the urban environment have established an Urban Geology Expert Group in order to tackle all the urban issues from the geosciences perspective. It is, therefore, highly probable that the urgently needed harmonised urban geochemical databases will be developed in the next few years.

(a) (b)

(c) (d) Figure 1. (a) Graph showing relationship between selected element concentrations in Earth Crust and human blood (Demetriades et al., 2018, Fig. 1, p.2); (b) distribution of total Pb in overburden, Lavrion, Hellas (Demetriades, 2011, Fig. 25.8, p.444); (c) distribution of total Pb in house dust, Lavrion, Hellas (Demetriades, 2011, Fig. 25.9, p.445), and (d) distribution of Pb in child blood, Lavrion, Hellas (Demetriades, 2011, Fig. 25.10, p.447).

References Demetriades, A., 2011. The Lavrion urban geochemistry study, Hellas. Chapter 25, In: C.C. Johnson, A. Demetriades, J. Locutura, R.T. Ottesen (Eds.), Mapping the chemical environment of urban areas. Wiley-Blackwell, John Wiley & Sons Ltd., Chichester, West Sussex, U.K., 424-456; http://doi.org/10.1002/9780470670071. Demetriades, A., Birke, M., 2015. Urban Topsoil Geochemical Mapping Manual (URGE II). EuroGeoSurveys, Brussels, 52 p.; http://www.eurogeosurveys.org/wp-content/uploads/2015/06/EGS_Urban_Topsoil_Geochemical_Mapping_Manual_URGE_II_HR_version.pdf. Demetriades, A., Birke, M., 2015. Urban Geochemical Mapping Manual: Sampling, Sample preparation, Laboratory analysis, Quality control check, Statistical processing and Map plotting. EuroGeoSurveys, Brussels, 162 p.; http://www.eurogeosurveys.org/wp-content/uploads/2015/10/Urban_Geochemical_Mapping_Manual.pdf. Demetriades, A., Johnson, C.C., Birke, M. (Guest Eds.), Urban Geochemical Mapping: The EuroGeoSurveys Geochemistry Expert Group’s URGE project. Special Issue, Journal of Geochemical Exploration 187, 213 p. Demetriades, A., Johnson, C.C., Birke, M., 2018. Editorial: Urban Geochemical Mapping: The EuroGeoSurveys Geochemistry Expert Group’s URGE project. In: Demetriades, A., Johnson, C.C., Birke, M. (Guest Eds.), Urban Geochemical Mapping: The EuroGeoSurveys Geochemistry Expert Group’s URGE project. Special Issue, Journal of Geochemical Exploration 187, 1-5. https://doi.org/10.1016/j.gexplo.2017.10.024. Hamilton, E.J., Minski, M.J., Cleary, J.J., 1973. The concentration and distribution of some stable elements in healthy human tissues from the United Kingdom: an environmental study. Sci. Total Environ. 1(4), 341–374; http://dx.doi.org/10.1016/0048-9697(73)90024-7. Johnson, C.C., Demetriades, A., Locutura, J. and Ottesen, R.T. (Eds.), 2011. Mapping the Chemical Environment of Urban Areas. Wiley-Blackwell, John Wiley & Sons Ltd., Chichester, West Sussex, UK, 616 p.; http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470747242.html.

ABSTRACT. Due to the fact that cadmium is classified as a potentially harmful element with respect to soil biological activity, plant metabolism and the health of humans and animals, there is concern over anthropogenic accumulations of Cd in the environment. It has no essential biological function, but it tends to accumulate in plants and aquatic biota, with consequent problems of toxicity. It is toxic to humans through the inhalation of dust, causing lung damage, and may cause cancer from long-term exposure, being also teratogenic and embryocidal. As soil is the main disposal and landfill receptor for different types of wastes, it is of great importance to carry out research which provides a necessary data on the element content in the Earth’s surface materials. Systematic geochemical mapping is a very effective tool of showing the geographic distribution of the elements, and environmental geochemical baseline data are urgently required to inform policy-makers and provide a sound basis for environmental legislation and resource management. The study area is located in southern Poland (in the Polish part of the Upper Silesian Coal Basin). It is a part of the Palaeozoic Variscan structure cut by numerous faults. The stratigraphic section is represented by the Triassic, Neogene and Quaternary systems (Wilanowski et al., 2009). The deposits of zinc and lead ores exploited in the past occurring in the Triassic ore-bearing dolomites were characterized as the largest and richest zinc and lead ore deposits in the world (Szuwarzyński, 1996; Viets et al., 1996; Paulo, Strzelska-Smakowska, 2000). For many years the most important sectors in the study area were coal mining and iron metallurgy, as well as zinc metallurgy in the past. The analysed area shows a diverse relief, locally highly altered as a result of industrial activity. There are many landfills of slag and mining waste near historical and present-day metal smelters. Since 1996, a detailed geochemical mapping project for this region (scale 1:25,000) has been conducted at the Polish Geological Institute. Until 2019, 17 map sheets have been developed and published in the form of separate atlases. The main objectives of this project were investigation of the environmental impacts of industry on soil contamination with heavy metals (including cadmium) and assessment of the degree of soils contamination. The obtained research results allowed determination of the geochemical baseline of cadmium in the region, controlled by natural factors, and indication of anthropogenically contaminated areas. The anthropogenic factors were associated mainly with former mining, processing and metallurgical industry of Zn-Pb ore, iron smelting, as well as hard coal mining and energy industry. The study was performed on soil samples from two depth intervals: 0.0−0.3 m (topsoil 22,663 samples) and 0.8−1.0 m (subsoil 19,307 samples), collected with a density grid of 16 samples/km2. Content of Cd in soils was determined by the inductively coupled plasma optical emission spectroscopy (ICP-OES) after samples digestion in aqua regia solution. Analysed topsoils had a wide range of such properties as pH (from very acidic to alkaline), TOC content (0.05–55.90%) and particle size distribution (from sandy to clay soils) showed their significant transformation. Anthropogenic transformations have led to so significant changes in the chemical composition of the soils in relation to the parent rocks that the basic geochemical features of the original rocks in the topsoil are very poorly visible. In areas of mining activity, around historical and modern metallurgical plants, as well as near mine heaps and waste dumps there are numerous anthropogenic anomalies of Ag, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb and Zn. The obtained results indicated great variation in Cd content in topsoils (<0.5–2,107.2 mg/kg; mean 4.3 mg/kg) and subsoils (<0.5–747.2 mg/kg; mean 2.2 mg/kg). Strong anomalies for Cd (Fig.1), as well as for Ag, As, Pb and Zn, are observed in the areas of historical Zn-Pb ore mining, former zinc smelters, and modern iron industry. About 25% of topsoil samples contained more than 4 mg/kg of Cd (Pb >144 mg/kg and Zn >419 mg/kg). About 25% of subsoil samples contained more than 0.7 mg/kg of Cd (Pb >33 mg/kg and Zn >101 mg/kg). The anthropogenic pollution sources in the natural environment encompass metallurgy of iron and non-ferrous metals, chemical and metal industries, mining of coal and its large-scale burning in power plants, historical exploitation and smelting of Pb-Zn ore, the impact of industrial waste (heaps of gangue and slag, settling ponds for sludge coal mud, mine water discharges), urbanization and transport.

ABSTRACT. Background Magnesite is closely associated with ophiolitic ultramafic rocks, more specifically dunites and chartzburgites, which can be altered at several extents due to different alteration episodes (e.g. serpentinization, carbonitization-silicification). In Northern Greece, the main magnesite ore deposits are located at Chalkidki area, more specifically, at Vavdos, Gerakini, Ormilia, Poligiros and Agia Paraskevi. Currently, magnesite is being mined at Gerakini and Ormilia sites by “Grecian Magnesite SA’ mining company. The study area of Gerakini hosts the ophiolitic sequence of Western Chalkidiki.

Objective Previous researchers have already provided mineralogical and geochemical data about ultramafic host rock-types, as well as magnesite (e.g. Papadopoulos, 2007, Skliros, 2013). In this study, the main objectives are to provide additional mineralogical and geochemical information, aiming to elucidate the mineralogical and geochemical differences of the different ultramafic lithological host rock-types, reveal their alteration history and thus to contribute to the understanding of magnesite formation.

Methods For the present study, seven (7) rock samples were taken from the Rachoni open pit mining site located at the Gerakini mining district. Thin-polished sections were mounted from each sample and were examined both in optical microscope and by means of scanning electron microscopy (SEM). Mineralogical composition of the collected samples was determined by X-Ray Diffraction (XRD) whereas supplementary information on the composition was received by Thermo-Gravimetric and Differential Thermal Analysis (TG-DTA) and Fourier-Transformed Infrared Spectroscopy (FT-IR). The chemical composition of the samples was determined by FUS-ICP-MS.

Results The studied samples can be divided into three different categories based on the degree and type of alteration they have undergone. The mineral assemblages of quartz+carbonates(dolomite+calcite)+spinels+chlorite, as well as the enrichment in SiO2 and CaO (Table 1) content of samples W1 and W2 are typical of listwanites. Listwanites are silica-carbonate-rich products of low-grade metasomatic processes after mafic and ultramafic rocks (Tsikouras et al., 2006 and references therein). More specifically, hydrothermal circulation of a CO2-rich fluid phase in a high water/rock ratio (Koutsovitis and Magganas, 2013) favor the formation of listwanites. The silification-carbonization reactions may well be responsible for the liberation of MgO from serpentine, suggesting an alternative source of Mg responsible for the magnesite formation. Sample W3 is consisted of vermiculite+quartz+serpentine+talc+amphibole+plagioclase+chlorite+magnesite. Notably, also small grains of zircon and monazite were observed with SEM. The extended presence of vermiculite indicate that this sample has undergone clay alteration apart from serpentinization (Serelis et al., 2004). Samples W4, W5, W6 and W7 mainly consist of olivine+serpentine+pyroxenes+spinels+magnetites+carbonates (magnesite+dolomite+calcite). These rocks are all typical magnesite-hosting serpentinites having undergone various degrees of serpentinization with their protoliths being dunites and hartzburgites. The chemical analyses of the studied samples are in agreement with the mineralogical investigation and the classification of these rocks in three different categories.

Table 1. Chemical composition of major and minor oxides in studied samples. Sample W1 W2 W3 W4 W5 W6 W7 SiO2 (wt.%) 64.92 65.31 40.63 41.8 37.22 35.02 36.63 Al2O3 (wt.%) 10.74 1.23 2.68 0.55 0.32 0.24 0.34 Fe2O3(t) (wt.%) 1.88 7.23 5.76 8.34 8.5 7.9 8.18 MnO (wt.%) 0.035 0.106 0.107 0.117 0.147 0.112 0.119 MgO (wt.%) 8.42 5.82 33.32 45.16 43.86 41.91 42.21 CaO (wt.%) 3.95 7.44 1.52 0.54 0.47 0.3 0.47 Na2O (wt.%) 2.95 0.05 0.1 < 0.01 < 0.01 < 0.01 < 0.01 K2O (wt.%) 0.38 0.06 0.01 < 0.01 < 0.01 < 0.01 < 0.01 TiO2 (wt.%) 0.078 0.051 0.045 0.007 0.004 0.003 0.004 P2O5 (wt.%) 0.02 0.04 0.02 0.01 0.01 < 0.01 < 0.01 LOI (wt.%) 6.87 12.47 15.96 3.5 9.49 14.43 12.35

Regarding the content of the samples in rare earth elements (REE), samples W4, W5, W6 and W7 contain very low REE concentrations, which is a typical characteristic of serpentinized ultramafic rock. On the contrary, the chondrite-normalized patterns of samples W1, W2 and W3 reveal higher REE concentrations, especially LREE.

Conclusions Considering the mineralogical and geochemical composition of the rock-types, serpentinization, carbonitization-silicification and clay alteration can be distinguished. Carbonatization-silicification suggests additional Mg source for the formation of magnesite. Ongoing research aims to the better understanding of the geologic history of the ultramafic rocks of the broader Gerakini-Ormilia area along with the magnesite ore formation at these localities.

Acknowledgements This research has been co‐financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH – CREATE – INNOVATE (project code:T1EDK-03543).

References Koutsovitis, P., Magganas, A., 2013. Mineralogy and geochemistry of listwanite occurrences from the Othris ophiolite, Greece. EGU General Assembly, Vienna, Austria., Geophysical Research Abstracts, 15, EGU2013-12712. Papadopoulos, A., 2007. Production and applications of commercial types of Klisoura bauxite and Gerakini magnesite. M.Sc. Thesis, Aristotle University of Thessaloniki, 130p. (in Greek) Serelis, K., Gartzos, E., Tsaousidou, P., 2004. Investigation of the alterations of the ultramafic rocks hosting magnesite ores at N. Evia. Proceedings of the 10th International Congress, Thessaloniki, Greece, Bulletin of the Geological Society of Greece, XXXVI, 377-386. (in Greek) Skliros, V., 2013. Investigation of the formation conditions of Vavdos and Gerakini (Central Chalkidiki) magnesite occurences and environmental applications utilization study. M.Sc. Thesis, University of Patras, 186 p. (in Greek). Tsikouras, B., Karipi, S., Grammatikopoulos, T., Hatzipanagiotou, K., 2006. Listwaenite evolution in the ophiolite melange of Iti Mountain (continental Central Greece). European Journal of Mineralogy, 18, 243-255.

ABSTRACT. Although electron microprobe analysis (EMPA) is the most common analytical method for the study of mineral chemistry, it cannot recognize the multiple oxidation states of transitional metals and, as a sequence, the Fe2+/Fe3+ ratio is calculated stoichiometric. In the case of spinels, this calculation method is applied assuming a proportion of 1 bivalent and 1 trivalent cation per 4 oxygens, thus ignoring the possibility of non-stoichiometry due to Fe3+ excess and cation vacancies in the lattice (Quintilani et al., 2006). For the determination of the actual Fe oxidation states in minerals, 57Fe Mössbauer spectroscopy (MS) has be proven to be a very effective method (Wood and Virgo, 1989, McCammon et al., 1998, Sobolev et al., 1999, Quintilani et al., 2006). The determination of the actual oxidation states of Fe and the attribution of Fe2+ and Fe3+ to the tetrahedrally and octahedrally coordinated T and M sites is spinels has been proven to be accurately calculated by the application of MS (e.g., Andreozzi et al., 2001, Hålenius et al., 2002, Quintilani et al., 2006). Furthermore, since Fe ratios of Cr-spinels are used for the estimation of fO2 by the Ballhaus et al. (1990) oxygen geobarometer and for the estimation of equilibrium temperatures by the Ballhaus et al. (1991) geothermometer, the determination of the actual oxidation states of Fe and their use in these estimations is valuable for the accurate reconstruction of the thermo-oxidative history Cr-spinels host rocks. The aim of this study is to present new MS data of spinels (chromites) from Vourinos ophiolitic sequence chromitites and compare the actual Fe oxidation states calculated by MS with the stoichiometric calculations based on EMPA. Four chromitite samples from three mining sites of Vourinos chromite mining district were used for this study: Xerolivado-Skoumtsa (2 samples), Aetoraches (1 sample) and Rizo (1 sample). All samples were examined in transmitted and reflected light optical microscopes. Mineral chemistry was determined with a JEOL 8200 electron microprobe equipped with a wavelength dispersive system (SEM-WDS). The system was operated using an accelerating voltage of 15 kV, a sample current on brass of 15 nA, a counting time of 20 s on the peaks and 10 s on the background. A series of natural minerals were used as standards. The approximate detection limit is 0.01 wt.% for each element. For each sample, 4-6 of unaltered Cr-spinel cores were analyzed and their compositions averaged to produce a statistical result. The samples were crashed, grained and, with the use of magnetic separator, chromite was separated from the other mineral phases present. These almost pure (>90 wt.%) chromite samples were analyzed by means of 57Fe Mossbauer spectroscopy. Fe2+ and Fe3+ cations based on four oxygen and the Fe3+/Fe2+ and Fe3+/ΣFe ratios calculated by different approaches are presented in Table 1, whereas MS spectra acquired for the four samples is presented in Figure 1.

Table 1. Calculations of Fe2+ and Fe3+ cations and Fe3+/Fe2+ and Fe3+/ΣFe ratios for the studied samples. Sample XER5 XER10 RIZ3 AET4

Parameter Method Fe2+ cations based on 4 (O) EMPA 0.348 0.359 0.338 0.330 Fe3+ cations based on 4 (O) EMPA 0.085 0.048 0.069 0.053 Fe3+/Fe2+ EMPA 0.246 0.135 0.205 0.161 Fe3+/ΣFe EMPA 0.197 0.119 0.170 0.139 Fe3+/Fe2+ MS 0.250 0.140 0.330 0.200 Fe3+/ΣFe MS 0.200 0.120 0.250 0.170

Comparison between spinel Fe3+ contents calculated by EMPA and measured by MS show significant differences: Fe3+ contents calculated by EMPA range between 11.9 to 19.7% of total Fe, whereas Fe3+ contents measured with MS range between 12 and 25%. In addition, the values of Fe3+MS content is higher in all samples compared to the Fe3+EMPA content. The differences observed in the Fe3+ contents by the different approaches are due to non-stoichiometry. MS can reveal the Fe3+ excess of Cr-spinels while the EMPA approach cannot (Bosi et al., 2004). Fe3+ excess is attributed the fact that during Cr-spinel oxidation, the only cations involved are Fe2+ and Fe3+. During this process, tetrahedrally coordinated Fe2+ oxidized to Fe3+ with the formation of a cation vacancy in the T site (Quintilani et al., 2006).

(a) (b)

(c) (d) Figure 1. MS spectra of Vourinos Cr-spinel samples recorded at 77 K: (a) XER10, (b) XER5, (c) RIZ3 and (d) AET4.

The difference is slight in samples from Xerolivado-Skoumtsa (Southern Vourinos-samples XER5 and XER10) and significant in samples from Northern Vourinos (Rizo-sample RIZ3 and Aetoraches-sample AET4). This fact implies higher oxidation degrees (Bosi et al., 2004) for Northern Vourinos Cr-spinels than of those from Southern Vourinos were oxidation seems to be insignificant, implying a relation between the degree of oxidation and provenance. Ongoing research is targeting the further investigation of the latter remark and the estimation of the geothermo-barometric conditions via the accurate quantification of Fe3+ that has been revealed by MS measurements.

Acknowledgements This research is implemented through IKY scholarships programme and co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the action entitled ”Reinforcement of Postdoctoral Researchers”, in the framework of the Operational Programme ”Human Resources Development Program, Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) 2014 – 2020.

References Andreozzi, G.B., Hålenius, U., Skogby, H., 2001. Spectroscopic active IVFe3+-VIFe3+ clusters in spinel-magnesioferrite solid solution crystals: a potential monitor for ordering in oxide spinels. Physics and Chemistry of Minerals, 28, 435-444. Ballhaus, C., Berry, R.F., Green, D.H., 1990. Oxygen fugacity controls in the Earth’s upper mantle. Nature, 349, 437-449. Ballhaus, C., Berry, R.F., Green, D.H., 1991. High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle. Contributions to Mineralogy and Petrology, 107, 27-40. Bosi, F., Andreozzi, G.B., Ferrini, V., Lucchesi, S., 2004. Behavior of cation vacancy in kenotetrahedral Cr-spinels from Albanian eastern belt ophiolites. American Mineralogist, 89, 1367-1373. Hålenius, U., Skogby, H., and Andreozzi, G.B. (2002) Influence of cation distribution on the optical absorption spectra of Fe3+-bearing spinel s.s.-hercynite crystals: evidence for electron transition in VIFe2+-VIFe3+ clusters. Physics and Chemistry of Minerals, 29, 319-330. McCammon, C.A., Chinn, I.L., Gurney, J.J., McCallum, M.E., 1998. Ferric iron content of mineral inclusions in diamonds from George Creek, Colorado determined using Mössbauer spectroscopy. Contributions to Mineralogy and Petrology, 133, 30-37. Quintilani, M., Andreozzi, G., Graziani, G., 2006. Fe2+ and Fe3+ quantification by different approaches and fO2 estimation for Albanian Cr-spinels. American Mineralogist, 91, 907-916. Sobolev, V.N., McCammon, C.A., Taylor, L.A., Snyder, G.A., Sobolev, N.V., 1999. Precise Mössbauer milliprobe determination of ferric iron in rockforming minerals and limitations of electron microprobe analysis. American Mineralogist, 84, 78-85. Wood, B.J., Virgo, D., 1989. Upper mantle oxidation state: Ferric iron contents of lherzolite spinels by 57Fe Mössbauer spectroscopy and resultant oxygen fugacities. Geochimica et Cosmochimica Acta, 53, 1277-1291.

ABSTRACT. Magnesite ore deposits are closely associated with ophiolitic ultramafic rocks -more specifically dunites and chartzburgites. Dunites consist mainly of olivine (>90% v/v), whereas in chartzburgites the main mineral phases are olivine and pyroxenes (ortho- and clino-). These rocks can be altered at several extents due to serpentinization, and their primary minerals are altered to different mineral phases (mainly serpentine) but even in cases of extended serpentinization, relics of the primary minerals remain unaltered. The mineral olivine belongs to the orthorhombic crystal system have a general chemical formula: X2SiO4, where X=Mg, Fe. The ratio of magnesium to iron varies between the two endmembers of the solid solution: forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa). Synthesis of olivine in laboratory experiments has shown that, depending on the physico-chemical conditions, Mg and Fe can be substituted in small extend by other bivalent cations (e.g. Zn, Ni, Mn) (Nord et al., 1982, Annersten et al., 1982, 1984a, 1984b, Ericsson et al., 1986). Geologically, Gerakini area belongs to the ophiolitic sequence of Western Chalkidiki. In Gerakini the –serpentinized- ultramafic formations hosts numerous magnesite ore deposits. Currently, magnesite is being mined at Gerakini by the company “Grecian Magnesite SA”. The main scope of this work is to provide new data about Fe inclusions found in olivine grains from the Gerakini ultramafic rocks. This is the first such report in Greece and –to the best of our knowledge- worldwide. For the present study several rock samples (serpentinized dunites and chartzburgites) were taken from the Rachoni open pit mining site located at the Gerakini mining district. Thin-polished sections were mounted from each sample and were examined both in optical microscope (transmitted and reflected light). Mineral chemistry was determined with a JEOL 8200 electron microprobe equipped with a wavelength dispersive system (SEM-WDS). The system was operated using an accelerating voltage of 15 kV, a sample current on brass of 15 nA, a counting time of 20 s on the peaks and 10 s on the background. A series of natural minerals were used as standards. In one of the studied samples (W5), the examination in the SEM revealed a very rare phenomenon: olivine grains in one particular area of the examined section had inclusions (Figure 1). EDS and WDS analyses from the inclusions showed that they consist solely of Fe. The study of the mineral chemistry of olivines from sample W5 (Table 1) did not reveal any notable differences between olivines hosting Fe inclusions and those not. All olivines are high forsteritic and Fo content in both cases has a constant value of 0.90 (Fo0.90Fa0.10). Also, NiO content of olivines is rather low (<0.44wt.%), but no Ni alloys were found during the microscopic study of the sections. Table 1. Mineral chemistry of olivine grains from sample W5. Analyses No 22-26 are from olivines with Fe incusions, whereas analyses No 31-35 are from olivines without inclusions. Analysis No 22 23 24 25 26 31 32 33 34 35 SiO2 41.59 41.51 41.75 41.30 41.16 41.65 41.75 41.31 41.31 41.74 TiO2 0.01 0.04 0.05 0.01 0.05 -- -- -- 0.01 -- Al2O3 -- -- -- 0.04 -- -- -- -- 0.02 0.02 Cr2O3 -- 0.01 -- -- -- -- 0.04 -- 0.04 0.03 FeO 9.04 8.98 8.94 9.03 8.96 9.17 8.97 9.01 8.89 8.94 MnO 0.12 0.15 0.15 0.15 0.10 0.08 0.13 0.11 0.10 0.14 MgO 49.66 50.00 49.58 49.60 49.61 49.73 49.74 49.84 50.06 49.38 NiO 0.36 0.39 0.41 0.44 0.32 0.36 0.29 0.36 0.38 0.39 CaO 0.03 0.03 0.02 0.03 0.03 0.03 0.02 0.01 0.01 0.01 Total 100.82 101.11 100.90 100.60 100.23 101.03 100.93 100.65 100.83 100.65

Fo 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90

The Fe inclusions must have segregated from magmas prior to or along with crystallization of olivine. The segregation of these inclusions, although minor amount, could result in Fe depletion in the evolved magmas (Bai et al., 2017). Of course, subsolidus equilibration between olivine and chromite (Mg2+ diffusion from chromite to olivine and Fe2+ from olivine to chromite at subsolidus temperature) is the most probable factor controlling the olivine chemical composition and its high Fo content. Conclusions During the microscopic and mineral chemistry investigation of the studied samples, Fe inclusions in olivine were found in olivine grains of one of the samples. These inclusions must have crystallized prior to or along with olivine grains. The high Fo content of olivines in the studied samples is attributed –mainly- to subsolidus equilibration between olivine and chromite and –to some extend- to the formation of these inclusions.

Acknowledgements This research has been co‐financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH – CREATE – INNOVATE (project code:T1EDK-03543).

References Annersten, H., Adetunji, J., Filippidis, A., 1984a. Cation ordering in Fe-Mn silicate olivines. American. Mineralogist, 69(11/12), 1110-1115. Annersten, H., Ericsson, T., Filippidis, A., 1982. Cation ordering in Ni-Fe olivines. American Mineralogist, 67(11/12), 1212-1217. Annersten, H., Filippidis, A., 1984b. Cation ordering in Ni-Fe olivines: reply. American Mineralogist, 69(1/2), 164. Bai, Y., Su, B.-X., Chen, C., Yang, S.-H., Liang, Z., Xiao, Y., Qin, K.-Z., Malaviarachchi, S.P.K., 2017. Base metal mineral segregation and Fe-Mg exchange inducing extreme compositions of olivine and chromite from the Xiadong Alaskan-type complex in the southern part of the Central Asian Orogenic Belt. Ore Geology Reviews, 90, 184-192. Ericsson, T., Filippidis, A., 1986. Cation ordering in the limited solid solution Fe2SiO4-Zn2SiO4. American Mineralogist, 71(11/12), 1502-1509. Nord, A.G., Annersten, H, Filippidis, A., 1982. The cation distribution in synthetic Mg-Fe-Ni olivines. American Mineralogist, 67(11/12), 1206-1211.

ABSTRACT. Rodingite is an infrequent lithology in Greek ophiolites. In this paper rodingitized rocks from the Vavdos ophiolite (west Chalkidiki, Greece) are studied for the first time. They are found in the crustal section of the ophiolite, dominated by gabbronorite and they are divided into two types a) as dikes cross-cutting the gabbronorite or b) as a narrow zone at the contact of gabbronorite with the peridotite. Relict textures in the rodingitized rocks, field relationships with the gabbronorite and their geochemical resemblance are in favor of a gabbroic protolith. Rodingites typically are related to serpentinization demonstrating the paragenesis diopside + garnet ± vesuvianite. However this is not the case for this study. In fact, after mineral chemical study, the rodingitized rocks are dominated by clinozoisite and actinolite. This is possible in the case of large equilibration of the serpentinization fluids with the gabbronorite, producing rodingitized rocks with a greenschist-like paragenesis.

ABSTRACT. Post-flood investigations contribute greatly to the hazard assessment in areas where catastrophic sedimentary processes are associated with extreme floods, through the analysis of the dominant sedimentary processes of the fans (Crosta & Frattini, 2004; Gaume & Borga, 2008). Structure from Motion techniques, and the use of Unmanned Aircraft Systems (UAS) in general, have been increasingly proved useful to post flood surveys (Andreadakis, Kapourani, Diakakis, Papaspyropoulos, & Filis, 2017; Tamminga, Eaton, & Hugenholtz, 2015). During November 2017, an extremely intense rainfall took place in West Attica. The highest precipitation levels were recorded on the high altitude areas west of Mandra and Nea Peramos. This resulted in extreme floods in the region that reached the towns, bringing destruction and 24 fatalities. The huge volume of surface runoff that reached 170 m3/s and 4 m in height above the ground surface in some spots (Diakakis et al., 2018), reactivated old landforms on which a large portion of Mandra was built, resulting in houses, factories and roads being seriously damaged. The present research focused on the intramontane alluvial fan of Katsimidi stream, a tributary of Agia Ekaterini stream that caused the disaster in Mandra settlement, and at a 4 km distance upstream (west). It can be considered a prime example of reactivation of a fan of Pleistocene origin, accompanied by a debris flow, in which boulders larger than 1 meter in diameter were detached and transported along the streambed and finally deposited over the fan surface (Figure 1). The aim of the study was mapping of the flood features on the fan in explicit detail, with the aid of photogrammetry mapping by an Unmanned Aircraft Vehicle.

ABSTRACT. The island of Taiwan is located at the convergent plate boundary between the Philippine Sea plate and the Eurasian plate (Shyu et al. 2005). It is the product of the ongoing collision between the Eurasian continental margin and the Luzon volcanic island arc, part of the Philippine Sea plate (e.g. Shyu et al. 2005, 2016). Currently, Taiwan is experiencing a double suturing. The Luzon volcanic arc is colliding with the Hengchun forearc ridge in the south, which is in turn colliding with the Eurasian continental margin. In the north both sutures are unstitching. As a result, Taiwan is composed of three lithospheric pieces of Taiwan: the Eurasian continental margin, the continental sliver, and the Luzon arc (e.g. Shyu et al. 2005, 2016). The two sutures are producing separate neotectonic belts along the western and eastern part of the island. Each collision belt matures and then decays progressively from south to north resulting in discrete steps, manifested as seven distinct neotectonic domains along the western belt and four along the eastern belt. Each domain define a distinctive assemblage of active structures (Shyu et al. 2005, 2016). Characteristic examples of neotectonic domains in the eastern part of Taiwan are the Hualien and Ryukyu domains, which comprise active faults capable of producing earthquakes with magnitudes varying from 7.0 to 8.0. As it is shown from the study of historical and recent seismicity of the island, the eastern part has been often struck by large and destructive earthquakes in 1811 (Μ=7.5), 1815 (Μ=7.7), 1882 (M=7.5) and 1951 (M=7.5). On February 6, 2018, an Mw 6.4 earthquake hit eastern Taiwan with epicenter close to the coastal area north of Hualien city and focal depth around 10 km. The main shock caused 17 casualties and 285 injured in the Hualien City. The most affected area was Hualien city with VII maximum intensity. This area is composed of metamorphic rocks of the Central Range overlain by sediments of the Longitudinal Valley, which are in turn overlain by alluvial deposits. Hualien city occupies an area founded on sediments of the Longitudinal Valley overlain by recent alluvial deposits. One of the major active faults of Taiwan, the Meilun fault, disrupts these recent formations. Moreover, it ruptured in the October 1951 earthquake and produced up to ~1.2 m of coseismic vertical offsets and up to ~2 m of sinistral offsets (Hsu 1955; Bonilla 1975, 1977). The onshore length of the fault is less than 10 km. This length appears to be too short considering that the 1951 earthquake had a magnitude of 7.3 (Hsu, 1962). Therefore, the fault may extend further offshore to the north (Shyu et al. 2005). The scientific team visited the 2018 earthquake-affected area in Eastern Taiwan and conducted a field macroseismic survey and a geological reconnaissance in order to assess the earthquake impact on the natural environment and the building stock in Hualien County and to study the factors controlling the distribution of the observed earthquake environmental effects (EEE, Lekkas et al., 2018). As regards building damage, the earthquake caused almost identical heavy structural damage, comprising collapse of the ground floors and tilting, to 6 multistory buildings in Hualien City, while the rest of the building stock suffered light non-structural damage or no damage at all. The common damage characteristic of the inspected buildings was the decomposition of the concrete in the columns of the ground floor due to crashing, resulting in failure of columns and the subsequent tilting, while the upper floors of the structures were left intact. The observed damage is the result of the synergy of the prevailing special ground conditions at each site, the effects of the vertical component of the earthquake ground motion on the performance of concrete and reinforcement of damaged buildings, the parameters of the ground shaking as well as the type, design and construction characteristics of the affected buildings. The earthquake also caused damage to infrastructures of Hualien. Cracks indicating left lateral displacement were observed in the superstructure of a bridge. Taking into account the distribution of building damage and the geological setting of Hualien city, it is concluded that all damage was arranged along or close to the Meilun fault that runs right underneath Hualien with a length of 5 km and a strike direction of N20°-55°E. As regards the EEE, secondary EEE comprising ground cracks, liquefaction phenomena and slope movements were generated. Ground cracks were observed in several sites in Hualien city characterized by different direction and offsets. They indicated dextral or sinistral stike-slip offset and extension or compression. It is significant to note that they were observed close to the damaged buildings. Liquefaction phenomena included ground cracks accompanied by ejection of sand-water mixture that covered parts of the asphalt pavement in the area east of Hualien airport and outside of the perimeter wall of the military base. Slope movements were generated along steep slopes associated with faults as well as along the high and steep slopes of the Taroko Gorge located north of Hualien city. Based on the distribution of the EEE in Hualien city, it is concluded that ground cracks and liquefaction phenomena were also observed close to or along the Meilun fault. Taking into account the application of radar interferometry techniques by several research teams and the detection of permanent ground dislocation of tectonic origin in Hualien city (Yen et al., 2018; Huang and Huang, 2018), it is concluded that the eastern coastal part of the city located east of the Meilun fault is characterized by remarkably large uplift and northeastward displacement, while its western part located west of the Meilun fault is subsided and southwestwards displaced. Thus, the resulted displacement discontinuity coincides with the already mapped Meilun fault. In conclusion, the spatial distribution of the environmental effects (ground cracks and liquefaction phenomena) and the building damage induced by the February 6, 2018, Mw 6.4 Hualien (Eastern Taiwan) earthquake is strongly related to and controlled by the Meilun fault which runs right underneath Hualien City. Moreover, the observed damages resulted from the synergy of several factors comprising the soil characteristics, the effects of the vertical component of the earthquake ground motion, the construction type and the presence of the Meilun fault, which strongly affected the mechanical properties of the surficial sediments and the bedrock along or close to its trace.

ABSTRACT. On September 28, 2018, at 10:21 UTC [18:02:44, WITA (Indonesia Central Standard Time)], an earthquake occurred in the western part of Sulawesi Island (Indonesia) and more specifically on the coastal Lende area. It was assessed as M 7.5 [United States Geological Survey (USGS)] or M 7.7 [Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG)]. The main shock is located onshore at a distance of 61 km north of Palu city and at depths of about 10 km. It was preceded by a foreshock with magnitude M 6.1 generated at 07:00 UTC [15:00, WITA (Indonesia Central Standard Time)] and located 55 km NNW of Palu at a depth of about 18 km (USGS). The fault plane solutions of the main shock demonstrated an almost N-S striking left lateral strike slip fault (USGS, GCMT, CPPT, IPGP, GFZ) in the very complex tectonic environment of the Southeastern Asia. Based on the spatial distribution of aftershocks, it is estimated that the fault length was over 150 km (Sassa and Takagawa, 2018). The affected Sulawesi Island is a K-shaped island located within the highly seismic active triple junction area between the Australian, Philippine and Sunda plates, which is composed of small rotating blocks bounded by active faults (Socquet et al., 2006). It is composed of four rapidly rotating crustal blocks: (1) the Makassar block, located in the southwestern part of Sulawesi, (2) the North Sula block, located in the northeastern part of Sulawesi, (3) the East Sulawesi block is pinched between the Makassar block and the North Sula block and (4) the Manado block, located at the northeastern end of the island (Socquet et al., 2006). 14 earthquake-induced tsunamis were recorded for Sulawesi Island between 1820 and 1982 (Soloviev et al., 1992). Since 1927, the Makassar Strait sustained the destructive effects of seven tsunamis (Prasetya et al., 2001). They are attributed to earthquakes involving main tsunamigenic tectonic structures comprising the Palu-Koro fault, which constitutes part of the Central Sulawesi fault system (Prasetya et al., 2001). In the case of the September 2018 earthquake, the most affected area was the Palu depression (Lekkas et al., 2018), along the boundary between the Makassar and the North Sula blocks. The most affected parts of Palu depression included the coastal areas of the Palu Bay and more specifically the onshore Palu valley, in the east of the Palu-Koro fault, which is considered as the causative fault based on the primary EEE observed on the field (Lekkas et al., 2018) and the analysis of teleseismic data and synthetic-aperture radar and satellite optical images (Bao et al., 2019). The environmental effects induced by the 2018 Palu earthquake are classified into primary and secondary effects (Lekkas et al., 2018). The primary earthquake environmental effects (EEE) include coseismic surface ruptures in the Palu City area, while the secondary EEE included tsunami waves, liquefaction phenomena and ground cracks in the Palu Bay area (Lekkas et al., 2018). The coseismic surface ruptures directed parallel and in an en echelon arrangement to the causative fault and resulted in deformation and destruction of the road network and buildings respectively. The deformed asphalt pavements as well as the adjacent damaged buildings along with the perimeter walls and railings reveal left lateral offset, which is in coincidence with the causative Palu-Koro fault. The liquefaction phenomena occurred in Balaroa and Petobo districts and along a riverbed south of Bilomaru, located SE of Palu City. They comprised liquefaction- and lateral spreading-initiated flow that have resulted the total destruction of Balaroa and Petobo neighborhoods in Central Palu, which were swallowed up in a wave of mud resulting in thousands of dead, injured and missing people. The ground cracks were observed as tension cracks close to sites with gravitational movements and lateral spreading and are attributed to the ground shaking. Among the most impressive EEE, the 2018 Palu earthquake triggered a tsunami that struck the western coastal part of the Central Sulawesi Province extending from Magapa area to Palu Bay located north and south of the earthquake epicenter respectively. The tsunami struck several settlements along the aforementioned coastal area with the Palu Bay being the worst affected area. The coastal part of Palu City was devastated. The destructive waves arrived up to 10 minutes after the generation of the earthquake. This fact allowed little to no time for early warning and left no time to the local population for early evacuation resulting in many fatalities and huge economic damage. The evacuation started as soon as the tsunami approached the coast. With inundation depth ranging from 2 to 5m locally and inundation distance of hundreds of meters, the waves devastated the Talise beach in Palu City, the Dongala village at the western tip of the Palu bay as well as all many villages along the coast of Palu bay claiming the life of thousands and resulting in heavy impact on buildings, infrastructures, mobile objects and the environment. Ιt is mainly attributed to the synergy of coseismic seabed displacement, submarine landslides and liquefied gravity flow within Palu bay. Factors enhancing the tsunami destructive characteristics and losses along the coastal areas of Palu Bay include: (a) the close proximity of the affected area to the epicenter of the main shock and to tsunamigenic source resulting in tsunami arrival times shorter than 10 minutes, low dispersion and cause extreme run-up, (b) the local bathymetry and seabed morphology, which is characterized by a very steep rise from the seafloor of North Makassar Straits with water depth of about 2500 m to the western coast of the Central Sulawesi province, (c) the coastal configuration of the affected area, which is composed of gulfs and a gently concave coastline that created a wave-guide, funneling effects on the tsunami wave energy, amplification of tsunami height and run up and enhanced damage along the coast of Palu Bay, (d) both local bathymetry and coastal configuration resulted in wave refraction and reflection. As regards the earthquake impact on the building stock, the earthquake caused non-structural and structural damage mainly in Palu city. Multistory reinforced concrete (R/C) hotels and malls suffered heavy structural damage resulting in partial or total collapse. The ground floor of the buildings collapsed, while the upper floors behaved as rigid bodies, resulting in toppling of the damaged structures. In contrast, wooden and steel-frame buildings suffered mainly non-structural damage by the earthquake ground motion. Severe structural damage were observed in monumental structures such as mosques. In the liquefaction-affected areas, the level of building destruction was almost complete with many buildings of all types being compressed together and wrecked into a soil and debris zone resulting in significant loss of life. In the tsunami affected areas, all wooden structures founded along the coastal front were totally washed away by the wave pressure and only their concrete foundations were left in place. In villages along the western coast of Palu Bay, some wooden structures with wooden foundation were detached from their foundations and transferred inland but not destroyed. The R/C buildings suffered typical tsunami-induced damage in the ground floor and in the first floor due to tsunami water pressure and impact with floating debris. Punching failure of brick infill walls under out-of-plane tsunami pressures were observed in the form of large circular openings in infill walls. Flexural failures of columns within their midheights are attributed to impact forces generated by floating debris. Based on our field survey on the tsunami affected area and on all already published official reports on the tsunami impact, the Integrated Tsunami Intensity Scale (ITIS 2012) is applied for the Palu tsunami. Tsunami quantities and the impact on humans, mobile objects, coastal infrastructure, the natural environment and buildings were taken into account for the tsunami intensity assessment. The maximum assigned intensity is XII.

ABSTRACT. The 2008 Movri Mountain earthquake Mw=6.4 was a destructive earthquake, affecting a significant part of the NW Peloponnese. The earthquake triggered serious ground hazards (surface ruptures, liquefactions, rock falls) and extensive damage to buildings along a 30 km long by 20 km wide area (fig. 1). This study is based on the data base compiled after the earthquake, enriched by remote sensing data that cover a time period of 72 years. The analysis is focused to the west slope of the Skolis Mountain, Western Greece. In this slope we mapped by field work and remote sensing rock fall occurrence and evolution over the last 72 years (fig. 2). We also recognized that over this period the rock falls increase their width, or their length. The terms of width and length are defined along strike or down slope the Skolis Mountain respectively. To improve the reliability of our rock fall evolution model, two different methods have been applied: a) temporal and spatial distribution and b) statistical analysis of rock fall sites, across the Skolis Mountain, over the period from 1945 to 2017. Our rock fall inventory includes 10 time intervals, based on aerial photo interpretation. Analysis and mapping are implemented in a Geographic Information System (ArcGIS). Overall, pre- and post- Movri Mountain earthquake mapping shows significant size changes in rock fall sites and dispersal of boulders (fig. 3). Most of the fallen boulders are characterized by almost rectilinear fall paths. Taluses developed at the base of the slope are supplied by a narrow channel that consisted of small blocks of rocks and boulders. During the Movri Mountain earthquakes rock fall channels migrated upwards and downwards, along pre-existing rock fall deposits. Our analysis shows that the local seismicity appears to have a crucial control on Skolis slope processes influencing rock mass strength resulting in the occurrence of reactivated and newly formed rock falls (fig. 2). These observations are significant for proposing a mechanism of taluses inflation and the isolated boulders tracks for the identification and mitigation of hazard in an area prominent to rock falls.

ABSTRACT. Slope instabilities along steep caldera walls of active volcanoes pose a significant hazard, especially when the human factor is also present. Synthetic Aperture Radar (SAR) interferometry is a well-established geodetic imaging technique for monitoring ground displacements. The circular shape of calderas introduces some restrictions for the global visualization of point-like displacement measurements, dictating the inspection, independently of each approximate linear segment of the terrain slopes. In the present study, Persistent Scatterers Interferometry (PSI) ground displacements from Copernicus Sentinel-1 mission are manipulated in such a way to “unfold” and visualize the entire caldera walls on a single vertical planar surface. Point cloud analysis tools, originated from Terrestrial Laser Scanning (TLS) techniques, are explored for the manipulation of PSI point clouds in three-dimensional space and projection into pre-selected planes. Such approach simplifies the actual inspection of the caldera walls, while allowing building a geospatial link between coordinates of the selected planar projection and the actual geolocation grid. Furthermore, the view of PSI in unfolded elevation grids is more effective, in particular to render displacement induced by gravity. It is demonstrated that the utilization of advanced analysis and visualization tools throughout disciplines can improve the assessment of the SAR interferometric results and lead to a more effective decision making process.

ABSTRACT. The Aegean Sea is an area prone to tsunami hazard. According to the tsunami catalogues, numerous tsunamis have occurred affecting several islands and their coastal settlements. Seismicity and volcanic activity, in combination with submarine landslides triggered by them, stand as the main causes of tsunamis in the entire Aegean Sea. Thera Island (Santorini), located in the South Aegean Sea, neighbors major tsunamigenic zones. Its topography and human activities increase the need of its vulnerability assessment. The coastal settlement of Kamari, situated in the eastern coast of the island, poses the highest physical, social and economic relative exposure to natural hazards. In order to quantify the relative vulnerability of buildings in Kamari, a ‘worst-case run-up scenario’ was developed, based on scientific research that links tsunami run-up to earthquake magnitude. To assess the vulnerability of the buildings within the inundation zone, the PTVA-3 analytic model was applied. A GIS software was used to analyze and visualize the results. The results indicate that 423 out of 849 buildings are located within the inundation zone. The degree of vulnerability in correlation with the use of the buildings, reveals that the possibility of damage to the economic and touristic facilities is significantly high.

ABSTRACT. On July 21, 2017 (22:31 UTC), a Mw 6.6 earthquake occurred off-shore the Kos Island, Greece. The epicenter is located in the marine area between Kos Island and Turkey's coasts in Gokova Bay. Shortly after the earthquake, tsunami waves hit the south-east coast of Kos and the coast of Mugla province in the Gokova Bay area. In order to assess the tsunami intensity, data regarding the tsunami impact and gathered from multiple sources on both the coastal zone of Kos and the eastern coast of Turkey, have been recorded, assigned against the ITIS2012, and mapped using ArcGIS. Interpolation methods have been used in order to display the impact zoning in the inundated areas. Primarily collected data (autopsy, photo material, drone recordings, witnesses testimonials) along with the web published data and preliminary scientific reports have been mapped and evaluated against ITIS2012. Data collectived from 48 different points around the tsunami affected area. Most of them are located in or closed to city of Kos (Greece) and city of Bodrum (Turkey). The results show limited, yet notable impact on each one of the ITIS2012 categories, escalating among the middle grades of the Scale, and classifying the event as a middle-intensity tsunami. The max intensity for Bodrum area in Turkey is estimated at VII/XII grade as for the same tsunami the max intensity for Kos area in Greece is estimated at VI/XII grade. This can be attributed to different morphology, possible different distance, different wave direction or coastal land use. Earthquake activity in Aegean Sea can easily generate tsunami waves and affect coastal humans and human’s activity. Applying the ITIS Scale to a middle-intensity event for the first time, showed that the individual ITIS2012 criteria successfully complemented each other creating an excellent zoned or point map. The main criteria categories that mostly defined e a medium-impact tsunami are: a) Quantities, b) Impact on human & c) mobile objects However needed direct field observation and direct data collect for better quality on every ITIS2012 category.

ABSTRACT. This research focus on land subsidence phenomena due to the overexploitation of the aquifer at the Valtonera village in West Macedonia, Greece. In this area, the overpupming of the aquifer by both the open pit coal mine and the wells for irrigation purposes have led to a significant drawdown of the ground water level, during the last decades. The tectonic and hydrogeological data in conjunction with the geotechnical parameters, trigger extensive land subsidence and surfaces ruptures which are causing significant damage to infrastructure, farmlands and road network. The main objects of this research are the simulation of the failure mechanism and the calculation of the differential vertical displacements using the Plaxis three-dimensional finite element code.

ABSTRACT. Introduction – Geology The study area is located at the broader area of Farsala (East Thessaly) and more specifically between the city of Farsala and its railway station. The main target of the geophysical survey was to investigate the subsurface litho-stratigraphic structure in order to assess the existence of two (2) possible fault zones. These zones were proposed in the primary Neotectonic Map of the area of Farsala, scale 1:25.000 (Fig. 1), produced by the Division of Dynamic Tectonics & Applied Geology of National Kapodistrian University of Athens in 2016, in the context of the Seismic Hazard Mapping of the Farsala broader area. The alpine formations are mostly observed at the southern and eastern part of the greater study area. The late Cretaceous Limestones and Dolomitic Limestones (L-DL) seem to dominate (Fig.1). They are observed as mid-plated to un-plated with marly intercalations. Moreover, the ophiolite formations exist (Fig.1), which consist of peridotites and serpentinites, underlying the limestones. The existing ophiolite masses overlay the Jurassic Schists, which consist of clayey schists-cherts with conglomerates and limestone intercalations. The post-alpine formations cover the broader part of the Farsala basin. The inner part is covered with fine-grained alluvial deposits comprised of clays, silts and sands (Fig.1). The outer areas of the basin, where the geophysical measurements were carried out, are covered with the proximal phases of scree and consist of clays, grains and sand alterations (Fig.1). The foothills of the area are covered by the semi-cohesive scree and talus cones (Fig.1). Geoelectrical research Fourteen (14) vertical electrical resistivity soundings (VES) were conducted, using the Schlumberger array, along a N-S profile and total length of 2590 m. It is a method indicated for such geological investigations (Alexopoulos and Dilalos, 2010). The maximum current electrode spacing (AB) was equal to 1000 m. An ABEM Terrameter system was used for the field measurements. The geophysical data were processed by applying the automatic method of Zohdy and Bisdorf (Zohdy, 1989), composing a “multilayer” model. Beyond that, the commercial software package IX1D by Interpex was used for the calculation of the “layered” model. The qualitative representation and adumbration of the general subsurface structure is shown in Figure 2, where the distribution of (true) resistivity is observed, based on the results of the multi-layered models (Zohdy, 1989). Therefore, between the VES 01-14-02, the resistivity distribution changes rapidly, almost in vertical direction, implying the existence of a lateral zone of geoelectrical discontinuity. Below VES 02-03-13, we observe a geoelectrical formation of high resistivity values (>200 Ohm.m), at shallow depths (<50m). Beyond that, from VES 05 to the southern end of the section a smooth, horizontal resistivity distribution is shown, with low resistivity values (5-15 Ohm.m) dominating in the upper part. Interpretation and Discussion The evaluation of the geoelectrical processing and the correlation with the geology of the area gives an overall image of the subsurface geological structure. The results of this procedure are illustrated in Figure 3, with a maximum depth of investigation equal to 200 meters. The boundaries of three different geological formations can be observed in this geological-geoelectrical section (Fig.3). Between VES 01 and 14, a lateral zone of tectonic discontinuity that clearly interrupts the subsurface layers was identified. The throw of this zone, based on the offset of the top of the carbonates, is almost 150 m, with the northern block downthrown with respect to the southern one. Below VES 14-02-03-13-04, the cohesive L-DL formation, with high resistivity values (240-500 Ohm.m) was identified at depths less than 25 m. The overlying formation is considered to be the semi-cohesive scree (ρ=30-60 Ohm.m). Furthermore, between VES 14 and 02 and at depths more than 150 m, the schist-chert formation has been investigated. Below VES 05 and 05, the top boundary of Limestones-Dolomitic Limestones dips smoothly to the south, down to the depth of 100 m. From this point and up to the southern end of the profile, the top boundary of the L-DLf is almost horizontal, at depths between 50-80 m. Across the whole section, the L-DL formation is covered by 20-100 m thick alluvial deposits of varying lithological composition (ρ=9-59 Ohm.m). These deposits have been suggested to host local aquifers (Rozos and Tzitziras, 2002). Conclusions Based on the geological interpretation of the geophysical survey (Fig. 3), the primary Neotectonic map of the area was modified. More specifically, the southern fault zones (Fig.1-green line) has been restricted to the edges of the hill area, since there is no geophysical evidence for its occurrence along the profile (as it was initially indicated). Additionally, the northern fault line (Fig.1-pink line), seems to have been relocated between the location of the soundings 01 and 14, with an estimated width of the zone equal to 120 meters. The verification of this fault zone, with similar characteristics to the ones of the local active fault zones of the area, implies but not necessarily proves its activity level. Acknowledgements The authors would like to thank Ms. Eyagelia Kalaboki and Ms. Augousta Salomidi for their contribution during the acquisition of the field measurements. The study was funded by SARG-NKUA, research account 70/3/13532.

ABSTRACT. Mount Etna is located close to the eastern coast of Sicily ( = 14.99 oE, =37.75 o N). With a height of ~3330m is considered as the highest volcano of Europe’s mainland while it is classified among the most active volcanos globally. Its activity started back in the middle Pleistocene, it is characterized as a composite volcano (cone-shaped mountain) while its eruptions are mostly of strombolian type (moderate bursts of expanding gases).Its last eruption took place on 24 December 2018 while two days later (26 December, 02:19 UTC) an earthquake of M=4.8 occurred ~15km to the ESE of the volcano, causing damage to the nearby city of Catania. In this paper we investigate the ionospheric turbulence from TEC observations before and during this recent Volcanic activity of Etna’s Volcano.

ABSTRACT. The purpose of this study is to investigate the aerodynamics of realistic ice particle analogues and contribute to the improvement of ice crystal aggregation models and climate models. The research includes laboratory experiments where 3D-printed analogues of ice particles, such as ice crystals and aggregates, that are released in a tank of a mixture of glycerol and water in order to achieve Reynolds numbers which are representative of the real ice particles falling in the atmosphere. The study explores the differential sedimentation of two ice particles, the change of their velocity as they fall relative to each other and how this change is affected by the decrease in pressure along the trajectory and the wake capture acceleration of the trailing particle near aggregation point. In the report various types of particles with different sizes are used such as hexagonal plates and stellar with plate in terms of relative velocity drag coefficient, area ratio and Reynolds number. It is found that when two crystals of the same type fall within reasonable separation distances in order to aggregate, the acceleration of the trailing particle is steady when it approaches the leading particle and when the vertical separation is close to 2 centimetres, then the wake capture takes effect and the trailing particle accelerates more. The results show that when the difference in length between the leading and the trailing particle is larger, then the acceleration of the trailing one is higher. In the results, it is found that some trailing particles can increase their velocity, relative to its own terminal velocity, by 130% near aggregation point. This applies when the leading particle is larger.

ABSTRACT. The main objective of this study is to evaluate the variability of meteorological parameters measured by two high altitude meteorological stations (OITI and KALLIDROMO) that have never been analyzed before, located in two mountainous Natura 2000 sites of Central Greece, in the Region of Sterea Ellada (Figure 1). The stations were settled in the framework of the Project: Conservation of priority forests and forest openings in "Ethnikos Drymos Oitis" and "Oros Kallidromo" of Sterea Ellada. The data sets recorded in the meteorological stations cover the periods 2014-2018. OITI is a weather station located in site Greveno, National Forest Park of Mt. Oiti (38°49'26.00"N - 22°16'57.00"E - 1896 m). KALLIDROMO is a weather station located in site Gravia, Mt. Kallidromo (38°44'29.87"N - 22°28'12.00"E - 998 m). The National Park of Mt. Oiti extends at altitudes of 400 – 2116 meters and includes most of the highest peaks of the mountain (except the highest, Pyrgos, at 2152 m). The Mt. Kallidromo extends at altitudes of 43–1393 meters.

ABSTRACT. Air pollution has been one of the first environmental problems to be addressed by the EU and for this reason clean air is considered essential to good health. Information availability and understanding of the air quality issue is essential part of tackling it with efficiency. Having the latter in mind, the Municipality of Thessaloniki has considered relative environmental actions as an important priority and made significant efforts to include them in its short-term and long-term, already developed, strategies. Through these strategies the Municipality became partner in three important EU funded projects that are dealing with indoor and outdoor air pollution monitoring actions, namely CUTLER, AIRTHINGS, and LIFE SMART IN'AIR. The successful implementation of these projects will add to the knowledge of indoor and outdoor air quality in the City of Thessaloniki, whereas, at the same time, will improve the resilience of the city and the well being of its citizens.

ABSTRACT. The Hellenic Survey of Geology and Mineral Exploration, in the frame of the project GEOCHART carried out marine geology research at the broader Volos urban area; the scope of this research was to define the present day situation of the gulf, establishing a detailed bathymetry, and to study the palaeogeographic evolution during the Upper Quaternary.

ABSTRACT. Almost three quarters of known volcanic activity on Earth occurs in underwater locations. The presence of active hydrothermal vent fields in such environments is a potential natural hazard for the environment, the society, and the economy. Despite its importance for risk assessment and risk mitigation, monitoring of the activity is impeded by the remoteness and the extreme conditions of underwater volcanoes. Kolumbo underwater volcano, 7 Km NE of Santorini island, featuring an active hydrothermal vent field, which has shown near–explosive dynamics in the recent years (Carey et al., 2013). CTD (conductivity, temperature, depth) time series from an earlier expedition in 2010–2011 (Bakalis et al., 2017), which investigated mainly the northern part of the vent field, have been used to develop an advanced mathematical model based on the Generalized Moments Method to describe the underlying mechanisms governing the hydrothermal vent activity. The model was further tested successfully in the inactive caldera near Nisyros Island (Dodecanese, Greece) (Bakalis et al., 2018). The submerged volcanic activity of Santorini and the large difference of population present on the island between the winter and summer seasons, all within a partially enclosed system, make Santorini and its nearby active hydrothermal vent fields (e.g. Kolumbo) an ideal place for detailed investigation. The main objective of this work is to study high¬–frequency recorded CTD data in the water column over the Santorini caldera and the active neighboring hydrothermal vent fields. The data will be used to create depth profiles of the oceanographic properties such as conductivity, temperature and salinity and map their anomalies over active vents. In 2017, GEOMAR in collaboration with the National and Kapodistrian University of Athens, used an Autonomous Underwater Vehicle (AUV) to investigate the evolution of the NE–trending Santorini–Kolumbo line, where it also collected CTD data. The mission lasted 25 days, 19 of which were onboard operations. Detailed CTD 3D profiles have been reconstructed from the raw data to study Kolumbo’s active hydrothermal vent field and Santorini’s vent field (Camilli et al., 2015) to a full extent. Here we present the results from the 15-hour survey held on the 25th March 2017, during the POS510 expedition targeting the Santorini vent field located in the North Basin of the Santorini Caldera, as seen in Figure 1. In Figure 2, the depth profiles of the Temperature (T), Conductivity (C), Salinity (S) and Sound Velocity(V) are presented, respectively. The change in temperature seems to follow a typical open–ocean CTD profile, with higher values near the surface and the thermocline zone, which tend to become smaller as the depth reaches its maximum values near the seafloor and above the vent field. This behavior is evident in the profiles of salinity, conductivity and sound velocity, as well. However, an anomaly emerges at the depth of 350m in the C and S profiles, as the CTD sensor is placed directly above the vent sources, as can be seen at the profiles recorded between 250 and 350 m. The anomaly is attributed to existing vent activity, which is not so intense as to change the local thermodynamics of the system and have a significant impact on the T profiles, but is recorded in the high–sensitivity C and S sensors, indicating that hydrothermal fluids are entering the water column from the crust in a weak, but continuous fashion. As the present results are the first ones produced from this expedition, they provide strong motivation for further investigation. CTD anomalies in depth profiles will be fully documented, while a 2D map of vent activity will be constructed from measurements at constant depth of AUV operation. These stepsare crucial towards developing a supervised machine–learning algorithm able to provide a reliable description of the dynamic conditions over the hydrothermal vent field in near–real–time fashion and potentially provide the means to predict explosive conditions. The impact on developing appropriate mechanisms and policies to avoid the associated natural hazard is expected to be immense.

ABSTRACT. An important component of volcanic activity in the southern Aegean Sea is focused along a linear feature known as the Christiana-Santorini-Kolumbo (CSK) rift (Nomikou et al., 2018). Running in a NE-SW direction, it hosts a number of volcanic centers of late Pliocene to Pleistocene age as part of the overall east-west trending Hellenic subduction zone south of the island of Crete. Natural hazards from the CSK rift pose significant threats to the eastern Mediterranean region. They include earthquakes, subaerial or submarine volcanic eruptions, gas release from volcanoes, tsunami inundation of neighboring coastlines due to eruptions or submarine landslides, and potential aviation impacts from volcanic ash plumes. Kolumbo volcanic chain lies just off the northeast coast of Santorini the consisting of 25 submarine cones and craters (Nomikou et al., 2012; Hooft et al., 2017), that extend in a NE-SW direction along the floor of Anhydros basin. The largest of these is Kolumbo crater, a 3 km diameter cone with a 1700 m wide crater, a rim as shallow as 18 m below sea level, and a flat crater floor 505 m below sea level. Kolumbo is currently the most active and dangerous submarine volcano in the Mediterranean Sea and its crater floor hosts a high-temperature hydrothermal field with active massive sulphide deposition of potential economic significance (Kilias et al., 2013). The 1650 eruption had significant impacts in the southern Aegean area. At least seventy people, who were in the sea offshore or along the NE coast of Santorini died, from asphyxiation by acidic gases. A large tsunami on 29 September caused widespread damage on Santorini and elsewhere within a 150 km radius (Ulrova et al., 2016). The first detailed bathymetric map of the Kolumbo volcano was produced in 2001 using the 20 kHz SB2120 swath system on R/V Aegean (Nomikou et al., 2012; 2013). Bathymetric data were also acquired on-board the R/V Marcus Langseth using the Simrad Kongsberg EM122 12 kHz multibeam echo sounder in 2015. For the first time, high resolution AUV (Autonomous Underwater Vehicle) data were collected during POS510 cruise, in 7 missions of AUV Abyss (GEOMAR) (Hannington et al., 2017), under the framework of the collaborative project “ANYDROS: Rifting and Hydrothermal Activity in the Cyclades Back-arc Basin”. The goal of this project was to understand the initiation of arc rifting and associated back-arc hydrothermal activity. The focus was on the CSK rift system and Santorini-Kolumbo volcanic line, one of the few places in today’s oceans where submarine rifting of a continental margin arc can be studied in its earliest stages. We present a new bathymetric map of Kolumbo volcano based on AUV bathymetry with 2m resolution which helps to map: a) the abrupt inner slopes of Kolumbo caldera, b) the active vent field at the northern part of the crater floor (485m depth), c) the lava dykes in the inner slopes, d) the mass wasting deposits in the inner slopes, e) the curvelinear scarps with inward dipping faces at the W-NW base of Kolumbo’s flanks (faults and/or remnant crater rims). Using developed autonomous underwater vehicles (AUVs) with capabilities to map the seafloor with higher resolution than is possible with hull-mounted or towed sonar systems so as to identify seafloor geomorphological characteristics and produce detailed morphotectonic and hazard maps of active volcanic areas.

ABSTRACT. Introduction: The present study focuses on the mapping of the coastal and submarine morphology of the Kamari coastal zone in Southeast Santorini Island. Furthermore, its aim is to illustrate the physiographic features and the displacement of the coastal area for the period 1945-2016. By collecting and processing spatial data, aerial photographs and satellite images, habitat and several vulnerability maps were created, in order to determine the erosion processes of the coastal area. Kamari is a popular tourist attraction with a coastal area at risk, due to its extensive urban development. In order to protect the coastal area, 4 groins and 2 detached parallel breakwaters were constructed in 1991.

Methods: In order to create the habitat map, bathymetric and echo-sounding data was collected with the use of a Side-Scan Sonar and processed through Sonar Wiz (version6) software. For the study of the historical coastline displacement during the 70-year period (1945-2016), coastlines from aerial photographs and satellite images were georeferenced, digitized and compared with the use of ArcGIS 10.4. Moreover, marine surficial sediment samples were collected and granulometric analysis was carried out in order to understand the sedimentary processes that take place in the area.

Results: From 1945 to 2016, Kamari coastline has retreated by 18.5 m. In general, the coastal zone presents a variation in the volume of sediment deposition, as the rate of erosion is quite large. Specifically, during the first 15 years, an enormous rate of erosion has been observed, which, at some areas, exceeds 52m. For the next 13 years (1960-1973), the deposited sediment has advanced in some areas at the coastline by more than 38m. The start of a corrosive course of the coast is observed during the period of 1978-2003. Groins and breakwaters were constructed in 1991, which decreased the erosion rate in the area. However, during the following years the beach has stabilized against erosion. In 2012 a disastrous storm hit the area of Kamari, causing catastrophic damages. Finally, during the period 2015-2016 the beach presents an average retreat of approximately 4 m when maximum retreat accounts as much as 26.8 m and a maximum accretion of 15.4 m.

Main Conclusions: Due to the high rate of human activity, the coastal zone of Kamari has been heavily influenced. Undoubtedly, the construction of the breakwaters was a catalyst factor which contributed to the reduction of erosion rate. However, although the sediment supply is sufficient, the rate of erosion is rising rapidly and the beach’s ability to recover almost non-existent. The intense annual winds and waves in the area, extensive settlement development and inadequate infrastructure exacerbate the erosion.

ABSTRACT. Zakynthos Island is located in the external part of the Hellenic Arc and in the east of the Hellenic Trench, which represents the convergence boundary between the African and Eurasian plates, and is one of the most tectonically and seismically active parts of the Mediterranean region (Papazachos and Papazachou, 1989, 1997, 2003; Lekkas et al., 1996-1997). Based on the seismicity catalogues of the permanent regional seismological network operated by the Aristotle University of Thessaloniki (AUTH, 2019) covering the period from 550 BC to 2018, it is concluded that many earthquakes with magnitudes larger than 5.0 have been concentrated in four zones around Zakynthos Island. These zones include significant seismic sources with high productivity and frequent occurrence of destructive earthquakes during historical and recent times (Lekkas et al., 1996-1997; Papazachos and Papazachou, 1989, 1997, 2003) and they are the following: (a) The western offshore Cephalonia and Lefkada area, where the prevailing active tectonic structure is the Cephalonia Transform Fault Zone (Scordilis et al., 1985). (b) Within the Zakynthos channel and the respective structural basin between Zakynthos Island and Peloponnese, which are affected by the westward offshore extensions of onshore faults to onshore western Peloponnese. More specifically for the area offshore eastern Zakynthos, major normal faults bound continental fault blocks and are characterized as active tectonic structures as revealed from the integration results of onshore neotectonic mapping (Lekkas et al., 2000; Papanikolaou et al., 2007) and local seismological observations (Papoulia et al., 2014). (c) The area south and southeast of Zakynthos Island, where Vp-velocity models and their tectonic interpretation showed that the southwestward extension of the NE-SW striking dextral strike-slip Western Achaia Fault Zone (WAFZ) from Northwestern Peloponnese to offshore southern Zakynthos prevails (Makris and Papoulia, 2014). (d) The area southwest of Zakynthos Island. This zone constitutes a downthrown block of the external Hellenides at the northern end of the Hellenic Trench and comprises tectonic structures like flat thrusts, strike-slip faults and normal faults, whose reactivations have resulted moderate seismicity (SEAHELLARC Working Group, 2014). More specifically, thrusting prevails over strike – slip or normal faulting (Kokinou et al., 2005, 2006), with the most important feature of this area being a 46-km-long NW-SE trending thrust system (SEAHELLARC Working Group, 2014). This system is responsible for the generation of the 1997 Mw 6.6 earthquake (SEAHELLARC Working Group, 2014) as well as for the October 26, 2018 Mw 6.8 offshore Zakynthos earthquake. Thrust events are also observed along the Hellenic subduction zone located west and southwest of Zakynthos Island (Kiratzi and Louvari, 2003). The last major episode of the geodynamic evolution of the Central Ionian Islands is the October 26, 2018, Mw 6.8 Zakynthos earthquake. It was generated offshore southwestern Zakynthos and it was predominantly felt on Zakynthos and throughout the Ionian Islands, Peloponnese and the mainland Greece fortunately with no casualties or injuries reported. As regards the environmental effects induced by the 2018 Zakynthos earthquake, secondary earthquake environmental effects were observed including slope failures, a small tsunami and asphalt-pitch seepages. Landslides and rockfalls were mainly generated in various parts of the island and more specifically along the steep coastal slopes and scarps in its northwestern part (e.g. Navagio beach, VIIESI 2007), in its southwestern part (e.g. along Mizithres beach, VIIESI 2007), in its central-eastern part (e.g. Panagoula and Kryoneri areas, VI-VIIESI 2007 and VIESI 2007 respectively). A small tsunami wave was generated offshore southwestern Zakynthos and was detected based on sea level changes (offset: 0.549 m) (VIESI 2007) that occurred after the earthquake and were recorded by the Katakolo (offshore central western Peloponnese) station of the Sea Level Station Monitoring Facility (https://goo.gl/wURcNs). Based on several witnesses, an increase in sea level of about half a meter were observed along the coast between Santa Maria di Leuca Cape and Otranto located in the eastern coast of the Salento peninsula (Italy). Data on historical and recent earthquakes generated in the Central Ionian Sea and the western Peloponnese and on their EEEs induced on Zakynthos Island were obtained from the following sources: (a) all major academic databases, search engines and sources for scientific research including GeoRef, Sciencedirect, Scopus, Springer, JSTOR etc, (b) official earthquake catalogues from universities, seismological institutes and observatories, (c) books and scientific articles containing catalogues or information of earthquakes and their EEEs in Zakynthos (e.g. Papazachos and Papazachou, 2003) or in the broader Zakynthos area (e.g. Lekkas et al., 1996-1997), (d) official field survey and reconnaissance reports (e.g. Lekkas and Mavroulis, 2018) and (e) official reports of scientific research projects (e.g. Lekkas, 1993). The complete seismic history of destructive historical and recent earthquakes comprises 20 significant earthquakes generated not only onshore Zakynthos Island but also offshore with great impact on population, natural environment, buildings and infrastructures. The impact on the natural environment comprises mainly secondary effects including hydrological anomalies, anomalous waves/tsunamis, ground cracks, slope movements, tree shaking and liquefaction phenomena. Primary effects have also been reported after strong earthquakes in Zakynthos Island including reactivation of faults and coseismic surface ruptures. In Zakynthos Island: (a) primary effects comprised fault reactivation during the 1513 earthquake and formation of coseismic surface ruptures during the January 1893 earthquake, (b) the observed hydrological anomalies included rising of the ground water level, increased discharge in wells, increased river flow, overflow of streams and subsequent flooding of the adjacent area and sulphureous gas emissions along with flames and burning of the adjacent vegetation, (c) the anomalous waves/tsunamis included sea withdrawal, roughness and violent agitation of the sea surface and small scale tsunamis resulting in cape sweeping by sea waves, coastal submergence and coastal inundation, (d) the detected ground cracks were observed in areas with loose recent sediments and instability conditions along river banks, close to geotechnically unstable areas and along with liquefaction phenomena and sulphureous gas emissions, (e) the triggered slope movements are classified as rockfalls, rockslides and landslides along high and steep inland and coastal slopes and scarps, (f) severe tree shaking and damage to vegetation due to the earthquake shaking was limited, (g) liquefaction phenomena were also limited to ejection of sand/water mixture along ground cracks and coastal subsidence, (h) phenomena related to the presence of asphalt-pitch in the coastal mire/swamp zone of Keri were also triggered by the generated earthquakes. These phenomena included boiling of asphalt and asphalt-pitch seepages in various sites of the earthquake-affected area and more specifically in the eastern onshore and offshore part of the Keri bay fault block. The following summarizing and concluding remarks are made. Anomalous waves/tsunamis are the most frequently reported EEE in the 20 historical and recent earthquakes of this study (11 out of 20 events), followed by the slope movements (10 out of 20), ground cracks (7 out of 20), hydrological anomalies (6 out of 20), liquefaction phenomena (4 out of 20) and hydrocarbon-related phenomena (4 out of 20). Primary effects are limited to fault reactivation (1 out of 20 events) and coseismic surface ruptures (1 out of 20). The maximum assigned local environmental seismic intensities are VIII-IXESI 2007 for the Northern Zakynthos fault block, VIIESI-07 for the western part of the Central Zakynthos fault block, VIII-IXESI 2007 for the eastern part of the Central Zakynthos fault block, IXESI 2007 for the Keri Bay fault block, VIIESI 2007 for the Southern Zakynthos fault block and VIIIESI 2007 for the Skopos Mt fault block. The most susceptible areas to the generation of EEE are the Skopos Mt fault block, which has been affected by EEE during 11 earthquakes, followed by the eastern part of the Central Zakynthos fault block with EEE during 9 earthquakes, the Keri Bay fault block affected by EEE during 5 earthquakes, the western part of the Central Zakynthos fault block affected 4 times, the Southern Zakynthos fault block affected 3 times and the Northern Zakynthos fault block only once.

ABSTRACT. In this study we used geodetic data from two Greek GNSS networks, operating during the 2014-2015 period when three (3) strong and shallow seismic events occurred in the central Ionian islands, Greece. The earthquakes occurred on 26 January 2014 13:55 UTC (moment magnitude Mw=6.1), 3 February 2014 03:08 UTC (Mw=5.9) and 17 November 2015 07:10 UTC (Mw=6.4). Based on the time series analysis of the coordinates of the permanent GNSS stations co-seismic offsets were calculated together with the pre- and post-seismic deformation that occured in this area.

ABSTRACT. The Gulf of Corinth (GoC) is a unique site for seismotectonic studies in Europe. The eastern side of the GoC is subject to extensional directions similar to the western, i.e. NNE-SSW (Armijo et al., 1996). The highest extensional rate is located in the western side (15 mm/yr), while in the eastern part it is constrained at 10 mm/yr. The main part of the deformation is found offshore, within the gulf (Briole et al., 2003). The gulf is dominated by normal faulting trending WNW-ESE. The geologic substratum in the eastern side is comprised of Permian and Upper Carboniferous formations. Lithology is generally dominated by limestones (Triassic-Cretaceous). Overlying, Pleistocene and Pliocene deposits are found. Finally, recent screes and alluvial deposits are located over the previous formation (IGME, 1971, 1984). The extension in the Eastern Gulf of Corinth (EGoC) is related to a highly segmented fault system. The main strike of these faults is E-W,although secondary directions (NW-SE and NE-SW) are also observed. The major structures in the study area are the Kaparelli, Erithres, Germeno and Mytikas faults (Ganas et al., 2013). The Kaparelli fault is anapproximately E-W striking, south dipping normal fault which consists of three segments (Kokkalas et al., 2005). Active tectonics in the EGoC have led to several major earthquakes since 1900, with moment magnitudes (Mw) ranging between 4.1 and 6.2 (Makropoulos et al., 2012). The largest events are the mainshocks of the Alkyonides sequence of February-March 1981, with three Mw>6.0 earthquakes causing extensive damage to buildings and infrastructure in the EGoC, as well as to Athens (Papazachos and Papazachou, 2003). Since then, seismicity has been scarce (e.g. Papadimitriou et al., 1999). However, small episodes of seismic outburst have been recorded. A prime example is the sequence that occurred close to the town of Vilia. A total of 560 events were located in 2013, with local magnitudes (ML) between 0.5 and 4.4 (Kaviris et al., 2014). The current study incorporates a comprehensive seismic catalogue from 1900 up to 2017 for the broader area of Vilia. Event information was acquired from four sources: (a) the updated and extended catalogue of Makropoulos et al. (2012) between 1900 and 2009, (b) the catalogue of the Seismological Laboratory of the National and Kapodistrian University of Athens between 2009 and 2016, (c) the detailed catalogue of the 2013 Vilia sequence (Kaviris et al., 2014) and (d) newly located events of a local sequence near Vilia during 2017. For the latter, the arrivals of the P- and S-waves were manually determined from local and regional recordings of stations belonging to the Hellenic Unified Seismological Network (HUSN). The location of the foci was later acquired using a local velocity model (Kaviris et al., 2014) and the Hypoinverse software (Klein, 2002). The 2017 catalogue contains 53 events. The spatial features of the 2013 sequence do not present a definite correlation with the faults mapped in the area. The plane defined by the spatial distribution of hypocentersis striking N58°E and dipping SE, where as the focal mechanism of the mainshock indicated a similar fault with a 46° dip, a N64°E strike and a -71° rake. Both, however, indicate the existence of NE-SW, SE-dipping structures. This is in agreement with the depths of the foci (concentrated between 7 and 15 km). However, it is important to note that the accuracy of the hypocentral locations is compromised by the sparse network. Only one station (VILL) was located in a small distance from the seismogenic area (approximately 12 km). Thus, the causative fault(s) for the 2013 sequence could be a blind normal fault, or the NE-SW, SE-dipping Korombili fault. The latter suggestion can be valid if we accept a much steeper fault than the one indicated by the focal mechanism of the mainshock; indeed, field mapping shows that this is a very steep fault (dip>65°), which could have a bi-planar or curved geometry, flattening down dip. In addition, a smaller, SSE dipping fault is also observed near Agios Vasileios village: this could also be connected to the 2013 sequence. Placed in a broader tectonic context, the fault(s) responsible for the 2013 events is located between major E-W normal and oblique-normal faults, such as the Erythres fault to the east, the Kaparelli fault to the north, the Mytikas and Germeno faults to the south and the Domvrena fault to the west, the latter being the northern marginal fault in the eastern part of the active GoC. The 2013 seismic activity, attributed to NE-SW faults, such as the Korombili fault and/or possible blind structures indicates a possible linkage between major E-W faults, such as the Kaparelli-Erythres and Domvrena faults. If this assumption is valid, then Mt Kithaironas can be considered as a transfer zone between major E-W faults; the Korombili fault can be acting as a link between the Kaparelli and Domvrena faults, defining the western border of the transfer zone; its eastern border is much less well defined, however, with only a few NE-SW minor faults mapped. The study of faulting in the EGoC is of great importance. As evidenced by the events of 1981, the knowledge of seismotectonics in an active area close to Athens, the largest metropolitan area in Greece, is crucial for improving the estimates of seismic hazard and for taking steps towards risk mitigation and refining the building code. A more detailed mapping of the faults in the area and the densification of the network can aid in identifying potential sources of intense tectonic activity.

ABSTRACT. The Central Ionian Islands, namely Kefalonia and Lefkada, consists the most seismically active area in the Mediterranean. The main tectonic characteristic is the dextral strike slip motion caused by the Kefalonia Transform Fault Zone (KTFZ) (Scordilis et al., 1985) along which strong earthquakes occur regularly for the past 600 years at least. Since 2003 four strong earthquakes (MW > 6.0) occurred in the area, both in Kefalonia (26/1/2014 and 3/2/2014) and Lefkada (14/8/2003 and 17/11/2015) and their aftershock sequences were adequately recorded and located since a local seismological network has been installed the day after the 2003 main shock (Karakostas et al., 2004), whereas the last one of them was recorded by an adequate number of permanent seismic stations, since the network was substantially improved since 2003. A permanent dense seismic network is in operation since mid-2014 (Hellenic Unified Seismological Network), resulted to microseismicity monitoring sufficient to reveal the complex faulting properties of the area. From September 2016 to December 2018 all recorded earthquakes in the area are manually picked and then located resulting in a adequately accurate earthquake catalog comprising about 13000 events (Figure 1), most of them along the Kefalonia Transform Fault.

The earthquakes are relocated using a recent 1D velocity model (Papadimitriou et al., 2017) considering station time delays by an iterative procedure (Karakostas and Papadimitriou, 2010) in order to account for the lateral crustal variations. The Double – Difference method is then applied and a cross – correlation algorithm (Waldhauser and Ellsworth, 2000, Schaff and Waldhauser, 2005) is implemented. The resulting spatial distribution is examined using strike parallel and strike normal cross sections detailing the major seismically active structures as well as the adjacent minor faults along the KTFZ. Benefiting from the azimuthal coverage of the seismic network focal mechanisms are calculated using moment tensor inversion (Sokos and Zahradnik, 2008) or first motion polarities (Reasenberg and Oppenheimer, 1985) in order to determine the rupture properties of the active structures in the area and, along with the relocated seismicity, reveal the kinematic properties of the faults. Seismicity on Lefkada Island is observed along the main fault zone as well as on several conjugate structures where mostly microseismicity is manifested with focal depths ranging from 5 to 15 km. In Kefalonia Island the seismicity follows more complex patterns. In its northern part and in the gulf of Myrtos seismicity reveals the existence of step overs between the two islands, in accordance with Karakostas et al., (2015), whereas along the Paliki Peninsula seismicity patterns appear more scattered, revealing small structures following the trend of the KTFZ with focal depths ranging from 5 to 18 km. In the offshore area South of Kefalonia several ML >4.0 were recorded and the resulting seismic activity is manifested by small clusters that follow the main fault zone at focal depths reaching about 20 km. In the area between Zakynhtos and Kefalonia a seismic excitation over a two month period led to the mapping of a well – defined cluster striking NE – SW with focal depths ranging between 15 and 20 km. The results contribute to the precise mapping of smaller active seismic sources, that are capable of producing light to moderate earthquakes and should be taken into account in seismic hazard assessment.

Acknowledgements This work gas been supported by the project “Helpos – Hellenic System for Lithosphere Monitoring” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure” funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014 – 2020) and co-financed by Greece and the European Union (European Regional Development Fund)

References Karakostas, V., Papadimitriou, E., Mesimeri, M., Gkarlaouni, C., Paradisopoulou, P., 2015. The 2014 Kefalonia Doublet (MW6.1 and MW6.0), central Ionian Islands, Greece: Seismotectonic implications along the Kefalonia transform fault zone. Acta Geophysica 63, 1–16. Karakostas, V.G., Papadimitriou, E.E., 2010. Fault complexity associated with the 14 August 2003 Mw6.2 Lefkada, Greece, aftershock sequence. Acta Geophysica 58, 838–854. Karakostas, V.G., Papadimitriou, E.E., Papazachos, C.B., 2004. Properties of the 2003 Lefkada, Ionian Islands, Greece, earthquake seismic sequence and seismicity triggering. Bull. Seismol. Soc. Am. 94, 1976–1981. Papadimitriou, E., Karakostas, V., Mesimeri, M., Chouliaras, G., Kourouklas, C., 2017. The Mw6.5 17 November 2015 Lefkada (Greece) Earthquake: Structural Interpretation by Means of the Aftershock Analysis. Pure Applied Geophysics 174, 3869–3888. Reasenberg, P., Oppenheimer, D.H., 1985. FPFIT, FPPLOT and FPPAGE; Fortran computer programs for calculating and displaying earthquake fault-plane solutions. U.S. Geological Survey Open-File Rep. 85-739. Schaff, D.P., Waldhauser, F., 2005. Waveform cross-correlation-based differential travel-time measurements at the northern California seismic network. Bulletin of the Seismological Society of America 95, 2446–2461. Scordilis, E.M., Karakaisis, G.F., Karacostas, B.G., Panagiotopoulos, D.G., Comninakis, P.E., Papazachos, B.C., 1985. Evidence for transform faulting in the Ionian sea: The Cephalonia island earthquake sequence of 1983. Pure Applied Geophysics 123, 388–397. Sokos, E.N., Zahradnik, J., 2008. ISOLA a Fortran code and a Matlab GUI to perform multiple-point source inversion of seismic data. Computers & Geosciences 34, 967–977. Waldhauser, F., Ellsworth, W.L., 2000. A Double-difference Earthquake location algorithm: Method and application to the Northern Hayward Fault, California. Bulletin of the Seismological Society of America 90, 1353–1368.

ABSTRACT. Our study investigates the temporal patterns of b-values in Central Ionian Islands during the last decade. This data-rich case study includes the January-February 2014 earthquake doublet of Kefalonia Island and the associated earthquakes and the 2015 sequence of Lefkada Island (Karakostas et al., 2015; Papadimitriou et al., 2017). For the interpretation of the temporal variations of b-values it is crucial to use high quality data and consistent earthquake catalogs compiled based on a homogeneous monitoring network. For that purpose we use a dataset with events occurred in Central Ionian Islands for the period between 2008 and 2017. The magnitude of completeness is computed through the application of the goodness-of-fit method (Wiemer and Wyss, 2000, Figure 1). For safety we add 0.1 and consequently, the magnitude threshold is set〖 M〗_th=2.8. The temporal evolution of b-values is analyzed by means of two different techniques (Tormann et al., 2013). The former is the constant – time – windows technique, where fixed length time windows are used to estimate b-values through time, and the latter is the fixed – number – of events approach. When applying the fixed – number – of – events approach we are based on the average annual number of events occurred in the selected period with M≥M_th. In our case, it is found that N ̅_ann=265 earthquakes. We show that changing the value of the number of events within reasonable limits (-50, 50) does not change the shape of the time-series. For the constant – time – windows technique, a wider variety of time windows is examined since both seismic excitation and relative quiescence are present in the dataset and an average period cannot be applied. The time windows range from a few months to 2 years. We argue that when significantly varying seismicity rates are observed in a region, like in the case examined, the approach of constant – time – windows is biased. On the one hand, small time windows are able to capture abrupt changes but then, when seismicity is relatively low, many empty bins are created, and on the other, large time windows fill all the bins but are not able to track immediate changes and provide detailed information. The red line in Figure 2, for example, which corresponds to a time window of 2 years, does not seem able to capture b-value variations due to the 2014 Kefalonia doublet and the 2015 Lefkada main shock, which are apparent to the black line. The overlap between successive b-value estimates is also investigated within different ranges from no overlap to continuously moving the window by one event at a time. The larger is the overlap the smaller is the sensitivity of choosing the starting point of the analysis and the larger are the details depicted in the time-series. Figure 2 shows an example of 80% overlap between successive windows. Summary In this study different techniques are investigated for a detailed analysis of the temporal evolution of b-values in the Central Ionian Islands area. This is particularly intriguing, since monitoring the evolution of b-values through time rather than a mere comparison of absolute b-values could be translated into changes in stress levels. Acknowledgements The financial support by the European Union and Greece (Partnership Agreement for the Development Framework 2014 -2020) under the Regional Operational Programme Ionian Islands 2014-2020, for the project “Telemachus – Innovative Operational Seismic Risk Management System in the Region of Ionian Islands” is gratefully acknowledged. References Cao, A M., Gao, S.S., 2002. Temporal variations of seismic b-values beneath northeastern Japan island arc. Geophysical Research Letters, 29(9), doi:10.1029/2001GL013775. Karakostas, V., Papadimitriou, E., Mesimeri, M., Gkarlaouni, Ch., Paradisopoulou, P. 2015. The 2014 Kefalonia doublet (Mw6.1 and Mw6.0) central Ionian Islands, Greece: seismotectonic implications along the Kefalonia transform fault zone. Acta Geophysica, 63, 1–16., doi:10.2478/s11600-014-0227-4. Papadimitriou, E., Karakostas, V., Mesimeri, M., Chouliaras, G., Kourouklas, Ch., 2017. The Mw6.5 17 November 2015 Lefkada (Greece) Earthquake: Structural Interpretation by Means of the Aftershock Analysis. Pure & Applied Geophysics, 174, 3869–3888. Tormann, T., Wiemer, S., Hardebeck, J., 2012. Earthquake recurrence models fail when earthquakes fail to reset the stress field. Geophysical Research Letters, 39, doi:10.1029/2012GL052913. Tormann,T., Wiemer, S., Metzger, S., Michael, A. J., Hardebeck, J. L., 2013. Size distribution of Parkfield’s microearthquakes reflects changes in surface creep rate. Geophysical Journal International, 193, 1474–1478. Wiemer, S., Wyss, M., 1997. Mapping the frequency-magnitude distribution in asperities: an improved technique to calculate recurrence times? Journal of Geophysical Research, 102, 15115–15128 Wiemer, S., Wyss, M., 2000. Minimum magnitude of complete reporting in earthquake catalogs: examples from Alaska, the western United States, and Japan. Bulletin of Seismological Society of America, 90, 859–869.

ABSTRACT. Introduction Τhe North Aegean Trough (NAT), is a ENE – WSW trending structural deep, that forms along the westward propagation of the North Anatolian Fault (NAF) (Le Pichon et al., 1984). Structural and basin analysis of NAT addressed mainly the tectonic fragmentation that led to the development of sub – basins forming in the Uppermost Miocene (Lalechos and Savoyat, 1979; Mascle and Martin, 1990). Moreover, the discovery of the Prinos and Espilon hydrocarbon fields to the NE of NAT in the 70s, led to an increased interest of the Upper Cenozoic evolution of the broader region. (Laigle et al., 2000; Beniest et al., 2016; Ferentinos et al., 2018). Objectives This study, focused on the western and central NAT, is derived exclusively from deep penetrating seismic reflection data. By processing and interpreting the digitally available data – set we proceed to the qualitative identification of the stratigraphic top, of the Upper Miocene (Messinian) and describe the seismic stratigraphy of the identified depositional units. A refined understanding of the sedimentary column, for the various depocenters in the area under investigation, will enhance the geological perception of the region and will update the knowledge on the structural mechanisms that formed the basins. Methods The available data set consists, by several two-dimensional (2D) seismic profiles (multichannel, PSDM). They were acquired as part of the SEISGRECE campaign (Vigner, 2002). The acquisition parameters consist of a 16-fold coverage with a source of 16 generator – injector air guns with a total volume of 31L, operated in single bubble mode along a multi-channel streamer (96 channels, 2.4 km long streamer). We focus on an area of 600 km2 defined as Central NAT (Fig.1). Characteristics such as: (a) the reflection continuity, (b) the geometry and architecture, (c) the frequency and (d) the amplitude of the reflectors are used in order to enhance the seismic stratigraphy of the region. Results The utilised seismic reflection system, achieved an acquisition penetration down to approximately 17 secs (Vigner, 2002). Due to the fact that the resolution diminishes below the upper 6 seconds and because we were interested in Upper Cenozoic seismic stratigraphy, the seismic profiles were processed vertically so that the upper 4 secs (TWT) were distinguished, allowing a more detailed insight in the upper sedimentary column. In the under-evaluation area (Central NAT), four major seismic stratigraphic units have been recognized (Fig.1) and characterized by different seismic signatures, separated by three major unconformities, as distinguished in other parts of the Aegean. The uppermost unit (Unit. 1) is characterized, by densely spaced, parallel reflectors, with relative high amplitude and continuity. The thickness of the unit, ranges from 150 ms along slope, increasing to 250 ms at the center of the basin. The underlying, second unit (Unit.2), demonstrates a similar seismic response with a set of rather well stratified reflector packages up to 500 ms, that rest unconformably over the underlying units. The third unit (Unit.3) interpreted below is bounded by a pronounced unconformity better expressed along slopes. A chaotic seismic response and intense faulting characterize this unit. It is predominantly differentiated by lower frequencies and its thickness varies from 150 to more than 650 ms basin-ward. Finally, the lower fourth unit (Unit. 4), is clearly distinguished due to, (a) an increase in seismic amplitude, (b) a characteristic internal signal blanking and (c) the presence of distinctive up – doming structures. The average thickness of this unit is around 300ms. Conclusions The mapped uppermost three seismic units in Central NAT are attributed to the Plio-Quaternary sediment fill of the basin. They are separated by two major unconformities that overlap the slopes of the basin. On the basis of the regional stratigraphy we attribute the three units to Upper Quaternary, Lower Quaternary and Pliocene respectively (Fig.01). The fourth unit represents the Upper Miocene (Messinian). In our proposed interpretation we highlight this distinct Unit 4 seismic reflector package, that overlaps unconformably over the basement and displays the acoustic characteristics of an evaporitic sequence (prominent acoustically turbulent-transparent unit). Available literature for the broad area of North Aegean Trough reports sceptical about the presence of Messinian evaporites in the western and central regions. Here we recognize a unit that displays clear reflection characteristics of an evaporitic sequence. Even though our study relies solely on the interpretation of seismic profiles, the proposed scenario is further supported by the identification through refraction tomography of an interval, of high velocity (4.1 km/s) between the unconsolidated sediment cover and the Alpine basement at the vicinity of the area (Le Pichon et al., 1984). This, correlates also, with the calculated PSDM velocities of 4.43 km/s by Vigner (2002) that are compatible with an evaporitic sequence. Moreover doming-like structures, visible in low penetration medium resolution records (Ferentinos, 1990; Rodriguez et al., 2018), clearly emanate from our clearly distinguished Unit 4. In the broader area of NAT there are some references hinting the presence of Messinian evaporates (Ferentinos, 1990; Mascle and Martin, 1990; Lalechos, 2000; Koukouvelas and Aydin, 2002; Sakellariou and Tsampouraki-Kraounaki, 2019). Acknowledgements We thank Professor Hirn from the Institut de Physique du Globe de Paris, for making available the multichannel seismic profiles. References Beniest, A. et al. (2016) ‘Interaction between trench retreat and Anatolian escape as recorded by neogene basins in the northern Aegean Sea’, Marine and Petroleum Geology. Elsevier Ltd, 77, pp. 30–42. doi: 10.1016/j.marpetgeo.2016.05.011. Ferentinos, G. (1990) ‘Offshore geological hazards in the Hellenic arc’, Marine Geotechnology, 9(4), pp. 261–277. doi: 10.1080/10641199009388244. Ferentinos, G. et al. (2018) ‘Propagation and termination of a strike slip fault in an extensional domain: The westward growth of the North Anatolian Fault into the Aegean Sea’, Tectonophysics. Elsevier, 745(April), pp. 183–195. doi: 10.1016/j.tecto.2018.08.003. Koukouvelas, I. K. and Aydin, A. (2002) ‘Fault structure and related basins of the North Aegean Sea and its surroundings’, Tectonics, 21(5), pp. 10-1-10–17. doi: 10.1029/2001TC901037. Laigle, M. et al. (2000) ‘North Aegean crustal deformation: An active fault imaged to 10 km depth by reflection seismic data’, Geology, 28(1), pp. 71–74. doi: 10.1130/0091-7613(2000)28. Lalechos, N. (2000) ‘Aegean Sea,Possible Oil Bearing Areas - Petroleum Geology’, Mineral Wealth, 115, pp. 43–70. Lalechos, N. and Savoyat, E. (1979) ‘La sedimentation Neogene dans le Fosse Nord Egeen’, VI Colloquiim on the Geology of the Aegean Region, 2, pp. 591–603. Mascle, J. and Martin, L. (1990) ‘Shallow structure and recent evolution of the Aegean Sea: A synthesis based on continuous reflection profiles’, Marine Geology, 94(4), pp. 271–299. doi: 10.1016/0025-3227(90)90060-W. Le Pichon, X., Lybéris, N. and Alvarez, F. (1984) ‘Subsidence history of the North Aegean Trough’, Geological Society, London, Special Publications, 17(1), pp. 727–741. doi: 10.1144/GSL.SP.1984.017.01.58. Rodriguez Mathieu, Dimitris Sakellariou, Christian Gorini, Nicolas Chamot-Rooke, Elia d’Acremont, Alexandre Nercessian, Konstantina Tsampouraki Kraounaki, Davide Oregioni, Matthias Delescluse, and A. J. (2018) ‘Seismic profiles across the North Anatolian Fault in the Aegean Sea’, EGU General Assembly Conference Abstracts, 20, p. 7426. doi: 10.13140/RG.2.2.17993.24164. Sakellariou, D. and Tsampouraki-Kraounaki, K. (2019) ‘Plio-Quaternary Extension and Strike-Slip Tectonics in the Aegean’, in Transform Plate Boundaries and Fracture Zones. Elsevier, pp. 339–374. doi: 10.1016/B978-0-12-812064-4.00014-1. Vigner, A. (2002) Images sismiques par réflexions verticale et grand-angle de la croûte en contexte extensif : les Cyclades et le Fossé Nord-Egéen. Paris, Institut de physique du globe. p.269.

ABSTRACT. The purpose of the study is the determination of the shoreline changes and the sediment processes along the beach of Marathon Bay, which is located at northeast Attica. In the area there are specific locations and constructions endangered due to coastal retreat. A lagoon was established in the study area 3.500 years BP as it is characterized by low elevations, gentle slopes and fine sediments. The survey of the coastal and marine geomorphology was carried out by acoustic scanning of the seafloor with an echo sounder and sonar side scan, topographical sections perpendicular to the shoreline along with collection and analysis of surface sediments. The quantification of long-term shoreline displacements was carried out by comparing historical and contemporary aerial photographs (1945, 1960, 1969, 1988, 1996, 2001, 2010) along with very high resolution satellite imagery (2012, 2014, 2015, 2016, 2017, 2018), not to mention the tracing of the coastline (2013) with Real Time Kinematics equipment (RTK-GNSS).Throughout the Marathon Bay relatively gentle slopes are formed onshore, combined with shallow depths not exceeding the maximum measured depth of-40 m. An extended submerged alluvial fan seems to have been created mainly by Oinoi River. The types of substrate and habitats were mainly constructed by non-cohesive materials (mainly sand). An extended meadow of Posidonia Oceanica and Penicillus capitatus is observed. Also an intense underwater berm is observed, about 50 meters from the shore, along the part of the coastline which is mostly exposed to south waves. The biggest part of Marathon Bay seems to be subjected to coastal erosion. At the center of the Bay, at the estuary of Kenourgio stream, the maximum rates of coastal retreat is noticed ( ̴0,35m/yr) from the mid-40’s to 70’s. The exposition of the coast to the southern waves, the reduced sediment supply from local rivers, due to the Marathon’s Dam, the sediment's composition and the sediment transport from the beach to the submerged berm due to Marathon coastal hydrodynamic regime are mainly responsible for the coastal retreat. A lower and steady rate of retracement seems to have prevailed since the 1970s and beyond.

ABSTRACT. In the present study, we investigate the stable oxygen (δ18Ο) and carbon (δ13C) isotope ratios, the total organic carbon (TOC) content, and the petroleum potential of the pre-evaporitic and evaporitic Messinian deposits (6.46–5.33 Ma) from continuous sections on Zakynthos Island, Greece. The pre-evaporitic sequence mainly consists of alternating massive and laminated marls with rare calcareous marl and calcarenite intercalations. It is conformably followed by the gypsum unit. Particularly, the study is focused on Kalamaki and Agios Sostis sections (Kontakiotis et al., 2016; Karakitsios et al., 2017; Vasiliev et al., 2019; Fig. 1).

Figure 1 Geological map of Zakynthos Island (Karakitsios et al., 2017). The regional location is indicated in the inset map. Z1, Z2, Z3, LA1, KB101, AK1, KY1 correspond to boreholes.

In Kalamaki section, the gypsum unit corresponds to Primary Lower Gypsum (PLG) deposits, consisting of a 108-m thick succession with eight gypsum-marl cycles and different gypsum facies (Karakitsios et al., 2017). In Agios Sostis section the gypsum unit is more than16 m thick, consisting of several alternations of primary and clastic gypsum which derived from the resedimentation of older PLG deposits (Karakitsios et al., 2017). The isotopic bulk values are greatly variable: in Kalamaki section, -3.75 to +8.8‰ for δ18Ο, and -9.42 to -0. 93‰ for δ13C, whereas in Agios Sostis section, -3.54 to -0.31‰ for δ18Ο and -7.74 to +0.08‰ for δ13C respectively. Isotope values of the Agios Sostis section clearly show a marine environment, whereas in Kalamaki, the relevant values imply influence of continental fresh water in an environment of highly evaporated solutions. The origin of continental water is also confirmed by the organic matter type (type III kerogen) and the presence of plant remains (leaves) in the samples. Total organic carbon (TOC) values in Kalamaki section range from 0.15 to 1.31 wt% in the pre-evaporitic sequence, and from 0.07 to 0.95 wt% in the shale layers of the Primary Lower Gypsum, whereas in in the post-evaporitic from 0.03 to 0.3 wt%. In terms of petroleum potential, many of the samples are immature, whereas some of them correspond to the mature oil stage. Nevertheless, the pre-evaporitic and evaporitic sequence present a fair to good hydrocarbon-generating potential. Although the onshore source rocks are partially immature due to insufficient thickness of the overburden sediments, that does not preclude the possibility that the same source rocks are mature for oil generation in the offshore area (between Zakynthos-and Peloponnesus) where they are covered by more than 3 km of Pliocene-Pleistocene sediments. Acknowledgements This research has been co-financed by the European Union (European Social Fund – ESF) and Greek National Funds through the Operational Program ‘Education and Life-long Learning’ of the National Strategic Reference Framework (NSRF) – Research Funding Program: THALIS-UOA-‘Messinian Salinity Crisis: the greatest Mediterranean environmental perturbation and its repercussions to the biota’. References Karakitsios, V., Roveri, M., Lugli, S., Manzi, V., Gennari, R., Antonarakou, A., Triantaphyllou, M., Agiadi, K., Kontakiotis, G., Kafousia, N., De Rafelis, M., 2017. A record of the Messinian Salinity Crisis in the eastern Ionian tectonically active domain (Greece, eastern Mediterranean). Basin Research 29(2): 203–233. DOI: 10.1111/bre.12173. [Journal Article] Kontakiotis, G., Karakitsios, V., Mortyn, P.G., Antonarakou, A., Drinia, H., Anastasakis, G., Agiadi, K., Kafousia, N., De Rafelis, M., 2016. New insights into the early Pliocene hydrographic dynamics and their relationship to the climatic evolution of the Mediterranean Sea. Palaeogeography, Palaeoclimatology, Palaeoecology 459: 348–364. [Journal Article] Vasiliev, I., Karakitsios, V., Bouloubassi, I., Agiadi, K., Kontakiotis, G., Antonarakou, A., Triantaphyllou, M., Gogou, A., Kafousia, N., de Rafélis, M., Zarkogiannis, S., Kaczmar, F., Parinos, C., Pasadakis, N., 2019. Large sea surface temperature, salinity, and productivity-preservation changes preceding the onset of the Messinian Salinity Crisis in the eastern Mediterranean Sea. Paleoceanography and Paleoclimatology. https://doi.org/10.1029/2018PA003438. [Journal Article]

ABSTRACT. The Aegean is the most rapidly deforming region in the Mediterranean, as evidenced from seismological and geodetic observations (McKenzie,1972; 1978; Jackson, 1994; Jackson and McKenzie, 1988). The Aegean is located between two lithospheric plates, the Eurasian and the African, that are converging in an approximately N-S direction with a rate ranging 2-4 cm/yr (Floyd et al., 2010). The deformation becomes more complicated, due to the collision of the Arabian plate with Eurasia, resulting to the westward motion of Turkey towards the Aegean. All the above-mentioned movements lead to a complex deformation pattern: (a) the northern Aegean is dominated by the right lateral strike-slip motion of the westernmost part of the North Anatolian fault (McNeill et al., 2004), (b) the central part of the Aegean is characterized by normal faulting and extension in an approximately N-S direction and (c) the southern part is characterized by a subduction zone along the Hellenic Arc, where intermediate depth earthquakes occur, leading to the formation of the Volcanic Arc. The average distance between the two arcs is 120 km. The subduction zone is characterized by a general NE dip direction. However, the located events along the Benioff zone indicate that the slip and the shape vary along an amphitheatric, asymmetrical scheme, presenting significant differences between its eastern and western parts. The above-mentioned complex deformation results in high seismic activity consisting of small-intermediate as well as large earthquakes (Papazachos et al., 1998). In a such complex environment, it is crucial to determine earthquake focal mechanisms of intermediate, as well as of large magnitude events for understanding physical processes on faults during earthquakes. It is worth noting that since 2007 all Greek seismological networks have been integrated into the Hellenic Unified Seismological Network (HUSN; Papanastassiou, 2011). This important effort has contributed to the increase of detectability as well as to the improvement of the location parameters of earthquakes. The Seismological Laboratory of the National and Kapodistrian University of Athens (SL-NKUA), by taking into account phases from Greek Seismological institutions, has compiled a data set of more than 180.000 events and 1000 focal mechanisms located in Greece and the surrounded areas for the time period 1996-2018. Since 2018, more than 20,000 events have been recorded by HUSN stations and ~150 fault plane solutions have been analyzed by SL-NKUA. The determination of the seismic source parameters is based on a software developed at SL-NKUA (Papadimitriou et al., 2012). Two different techniques were applied to determine the source parameters of the selected earthquakes: a) Teleseismic body-wave modelling using waveforms at epicentral distances between 30 and 90 was employed for the large events (Mw > 5.8). Synthetic seismograms of P, SV and SH were calculated, taking into account the geometric spreading, the Earth’s radius, the radiation pattern of the considered component, the density, the angle of incidence at the source and the receiver as well as the free surface effect. b) For local to regional distances, the method of the P-wave first-motion polarities has been, for several years, the only one to constrain focal mechanisms. The installation of regional seismological networks worldwide, gave the opportunity to develop new methods based on the generation of synthetic waves using inversion techniques (Dreger and Helmberger, 1990; Fukuyama and Dreger, 2000; Ichinose et al., 2003; Kiratzi and Louvari, 2003). The main advantage of this approach is that moderate events can be analyzed in order to obtain reliable solutions. Thus, the knowledge on the type of the earthquake rupture is increased and contributes to the seismotectonic analysis of the study area. These techniques are based on the calculation of synthetics representing the complete wavefield, using the frequency–wavenumber method at local-regional distances (Bouchon, 2003). This method, applied in the present study, calculates synthetic waveforms directly comparable with the observed ones for a given velocity structure. Synthetics were generated by computing 9 fundamental Green’s functions, which are then combined with the elements of a moment tensor to produce the tangential, radial and vertical component of motion. The number of fault plane solutions based on moment tensor inversion for moderate magnitude events (M>3.5) is increasing the last years due to the quality and the density of broad band seismological stations. In this study, well-constrained focal mechanisms using the above-mentioned moment tensor inversion technique are presented and analyzed. The determined focal mechanisms can be viewed, selected and exported through an online platform at the web-site of the Department of Geophysics-Geothermics of NKUA (Fig. 1). The local-regional stress deducing from the focal mechanisms improves the knowledge of the physical state of the local seismogenic structures. This is important, considering that, in the same area, the type of the fault plane solutions of the moderate events has no significant differences in comparison with the type of the large ones. The recent calculated focal mechanisms in the broader area of Zakynthos (not only the aftershocks) indicate small differences from the main event of the 25 November 2018. Complexity of the focal mechanisms type is observed mainly southern of Greece along the Hellenic Arc. Acknowledgements We acknowledge support of this study by the project “HELPOS – Hellenic Plate Observing System” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

References Bouchon, M., 2003. A Review of the Discrete Wavenumber Method. Pure Appl. Geophys. 160, 445–465. Dreger, D., and Helmberger, D., 1990. Broadband modelling of local earthquakes. Bull. Seismol. Soc. Am.,. 80, 1162–1179. Fan, G., Ni, J.F., Wallace, T.C., 1994. Active tectonics of the Pamirs and Karakorum. J. Geophys. Res. 99, 7131–7160. Floyd, M.A., Billiris, H., Paradissis, D., Veis, G., Avallone, A., Briole, P., McClusky, S., Nocquet, J.-M., Palamartchouk, K., Parsons, B., England, P.C., 2010. A new velocity field for Greece: Implications for the kinematics and dynamics of the Aegean. J. Geophys. Res. 115, B10403. doi:10.1029/2009JB007040 Fukuyama, E. & Dreger, D.S., 2000. Performance test of an automated moment tensor determination system for the future “Tokai” earthquake, Earth Planets Space, 52, 383–392. Ichinose, G., Anderson, J., Smith, K. & Zeng, Y., 2003. Source parameters of Eastern California and Western Nevada earthquakes from regional moment tensor inversion, Bull. seism. Soc. Am., 93, 61–84. Jackson, J., 1994. Active Tectonics of the Aegean Region. Annu. Rev. Earth Planet. Sci. 22, 239–271. Jackson, J. and McKenzie, D., 1988. Rates of active deformation in the Aegean Sea and surrounding regions. Basin Res., 1, 121-128. Kiratzi, A., and Louvari, E., 2003. Focal mechanisms of shallow earthquakes in the Aegean Sea and the surrounding lands determined by waveform modelling: a new database. J. Geodyn., 36, 251–274. McKenzie, D., 1972. Active tectonics of the Mediterranean region. Geophys. J. R. astr. Soc., 30, 109-185. McKenzie, D., 1978. Some remarks on the development of sedimentary basins. Earth Planet. Sci. Lett. 40, 25–32. McNeill, L.C., Mille, A., Minshull, T.A., Bull, J.M., Kenyon, N.H., Ivanov, M., 2004. Extension of the North Anatolian Fault into the North Aegean Trough: Evidence for transtension, strain partitioning, and analogues for Sea of Marmara basin models. Tectonics 23, TC2016. doi:10.1029/2002TC001490 Papadimitriou, P., Chousianitis, K., Agalos, A., Moshou, A., Lagios, E., Makropoulos, K., 2012. The spatially extended 2006 April Zakynthos (Ionian Islands, Greece) seismic sequence and evidence for stress transfer. Geophys. J. Int. 190, 1025–1040. Papadimitriou, P., et al., 2018. The 12 th June 2017 M w = 6.3 Lesvos earthquake from detailed seismological observations. J. Geodyn. 115, 23–42. doi:10.1016/j.jog.2018.01.009 Papanastassiou D. 2011. Earthquake detection-location capability of the Hellenic Unified Seismological Network (HUSN) operating by the Institute of Geodynamics, National Observatory of Athens. Hellenic J Geosc 45: 209–216. Papazachos, B.C., Papadimitriou, E.E., Kiratzi, A.A., Papazachos, C.B. and Louvari, E., 1998. Fault plane solutions in the Aegean Sea and the surrounding area and their tectonic implication. Boll. Geof. Teor. App., 39, 199-218.

ABSTRACT. The recent activity in the broader area of Hellenic Volcanic Arc (HVA) highlights the importance of continuous monitoring of selected volcanic centers (Papadimitriou et al., 2015). Volcanic activity is often accompanied by precursors which are related to the movement of magma, causing localized increase of stress, developing cracks and fissures in the crust and triggering seismicity. These effects can be investigated by local seismological networks that permit earthquakes and ambient seismic motions to be recorded and analyzed. The construction of high precision catalogues of earthquake hypocenters can enhance the spatiotemporal distribution, highlighting activated structures and revealing pertinent seismicity migration patterns that may be related to the diffusion of magmatic process. Due to lack of data in the HVA, the case of 2018 Kilauea eruption will be examined, where high-quality seismological data were used in order to recognize certain seismic precursory patterns.

Kīlauea is an active shield volcano and the most active of the five volcanoes that form the island of Hawaii. Located along the southern shore of the island, the volcano is between 210,000 and 280,000 years old and emerged above sea level about 100,000 years ago. It is the second youngest product of the Hawaiian hotspot and the current eruptive center of the Hawaiian-Emperor seamount chain. Kilauea Volcano nestles on the southeast slope of Mauna Loa and merges so imperceptibly with its giant neighbor that significant dimensions cannot be assigned. Hawaiian volcanoes can erupt either at their summits or on their flanks. Summit eruptions of Kilauea occur within or near its caldera. Flank eruptions usually take place along rift zones, which are highly fractured zones of weakness within the volcano (e.g. Bevins et al., 1988; Carey et al., 2015). The most recent major eruption at Kīlauea had the longest duration of any other observed eruption. The current Kīlauea eruption began on January 3rd, 1983, along the eastern rift zone and resulted in the construction of the Pu'u'O'o cone. In 1986, activity shifted down the rift to a new vent, named Kūpa’ianahā, where it took on a more effusive character (Bevins et al., 1988). The Island of Hawaii experiences intense microseismic activity each year. Most of Hawaii's earthquakes are directly related to volcanic activity. These events may occur before or during an eruption, or they may result from the underground movement of magma that comes close to the surface but does not erupt. During the last decades (1983-today) the area of Kilauea has been characterized by intense seismic activity (Kirby and Klein, 2006). In this study, we collected and processed earthquake waveforms recorded by the Hawaiian Volcano Observatory (HVO) seismological network, providing P- and S-wave phase arrival-time data for events that occurred in the period April 2018-May 2018. The obtained catalogue contains phase data for more than 500 microearthquakes. A preliminary hypocenter location has been performed for the seismicity of the broader area, using the HYPOINVERSE code (Klein, 1989) and a custom 1-D velocity model. The waveform data of HVO were acquired from the Incorporated Research Institutions for Seismology (IRIS) (http://service.iris.edu/) via the International Federation of Digital Seismograph Networks web-services (FDSN-WS) data request protocol, facilitating prompt data availability. A subset of the phase data was employed in order to investigate the average Vp/Vs ratio and local 1-D velocity structure, using the mean travel-time residuals and location uncertainties (RMS, ERH, ERZ) minimization method (e.g. Kissling et al., 1994). The broader area of Kilauea and the Lower East Rift Zone (LERZ) showed several signs of volcano unrest leading up to the events of May-August 2018. Clustered activity of VT-earthquakes along a ENE-WSW fault zone, in Lower East Rift Zone (LERZ), has been identified during April 30th-May 3rd, 2018. The density of the HVO seismic network made feasible the categorization of the event type according to the source properties and, hence, the origin of the excitation (either volcanic or tectonic). During LERZ eruption, three main classes of seismic signals were discriminated: Volcano-Tectonic (VT), Long-Period (LP) and Hybrid (HB) earthquakes (Zobin, 2003). The classification of volcanic earthquakes was performed by visual inspection. The signals were selected from nearby seismic stations of the HVO at distances of 0.5 km to 20 km from the active fissures respectively. High amplitude volcanic tremor began on May 2nd following a swarm of VTs, as the real-time seismic amplitude measurement (RSAM) plot clearly showed. May 4th, 2018 M6.9 earthquake resulted to the collapse of the Pu'u'O'o cone, opening twenty (20) new fissures and to the interaction of magma with the water table in Halema’uma’u crater. Since May 17th, this interaction has led to a series of volcanic explosions of energy equivalent to M5.0 earthquakes that were connected to the inflation-deflation cycles of Kilauea volcano (USGS, 2018; Neal et al., 2019).

References Bevins, D., Takahashi, T. J. & Wright, T. L., 1988. The early serial publications of the Hawaiian Volcano Observatory: Volume 3, Monthly Bulletin of the Hawaiian Volcano Observatory (1821-1929), 1224 pp. Carey, R. J., Cayol, V., Poland, M., Weis, D., 2015. Hawaiian Volcanoes: From Source to Surface. Geophysical Monograph Series doi:10.1002/9781118872079 Klein, F.W., 1989. HYPOINVERSE, a program for VAX computers to solve for earthquake locations and magnitudes. U.S. Geological Survey Open-File Report: 89-314. Kirby, S. H., and Klein, F. W., 2006. The 15 October 2006-to-present earthquakes beneath the island of Hawaii: implications for Pacific plate flexure and geomechanical effects of ascendingCO2 that embrittles the Pacific plate mantle, Eos Transactions AGU,87(52), Fall MeetingSupplement, Abstract 253E-07. Kissling, E., Ellsworth, W.L., Eberhart-Phillips, D. and Kradolfer, U., 1994. Initial reference models in local earthquake tomography. J. Geophys. Res. 99, 19635-19646. Neal, C. A. et al., 2019. The 2018 rift eruption and summit collapse of Kīlauea Volcano, Science, Vol. 363, Issue 6425, pp. 367-374 DOI: 10.1126/science.aav7046 Papadimitriou, P., Kapetanidis, V., Karakonstantis, A., Kaviris, G., Voulgaris, N. and Makropoulos, K., 2015. The Santorini Volcanic Complex: A detailed multi-parameter seismological approach with emphasis on the 2011-2012 unrest period. J. Geodynamics, 85, 32-57. USGS, 2018. Preliminary Analysis of the ongoing Lower East Rift Zone (LERZ) eruption of Kīlauea Volcano: Fissure 8 Prognosis and Ongoing Hazards, COOPERATOR REPORT TO HAWAII COUNTYCIVIL DEFENSE, 15 pp. Zobin, V.M., 2003. Introduction to Volcanic Seismology, Elsevier Science, 308pp.

ABSTRACT. The project HELPOS – Hellenic System for Lithosphere Monitoring, Greece aims to create/upgrade a unified network to record the ground motion with the use of a variety of sensors. Among the HELPOS goals is to build urban accelerometer networks such as the dense Strong Ground Motion (SGM) network that have been installed in the Chania basin. The dense SGM networks aiming to continuously monitor the ground motion in urban environments and present the results in enhanced detail shakemaps, especially in areas where high variations in the Peak Ground Acceleration (PGA) values due to the local site effects are observed.

ABSTRACT. Chailas et al. (2010) presented a unified and homogenized aeromagnetic map of the Greek mainland. In the frame of HELPOS a new enriched, re-interpreted and homogenized, aeromagnetic map of Greece is being compiled. In the new version new areas were added to the previous map, and the data were re-assessed prior to the final compilation in order to both use incorporate the definite IGRF model and, diminish the effect of topography. As it will be shown here the improvement of the resulted map is of the order of some tens of nT.

Chailas, S., Tzanis, A., Kranis, H., Karmis, P., 2010. Compilation of a Unified and Homogeneous Aeromagnetic Map of the Greek Mainland. 12th Int. Conference of the Geol. Soc. Greece, Bull. Geol. Soc. Greece, XLIII, No4, pp. 1919- 1929.

ABSTRACT. This study examines the ground motion pulses during events which occurred in strike slip faults in order to show rupture directivity. Earthquake directivity is the focusing of wave energy along the fault in the direction of rupture. Observations from previous studies have displayed the effects of near-fault ground motions and suggested the forward and backward rupture directivity (Cocco, 1997; Somerville et al., 1997; Koketsu and Miyake, 2008; Poiata et al., 2012; Kane et al., 2013). Forward rupture directivity effects occur when the rupture front propagates toward the site, and the direction of slip on the fault is aligned with the site. Conversely backward directivity effects occur when the rupture propagates away from the site. Rupture directivity effects cause spatial variations in ground motion amplitudes and duration around faults. If a site is located in the forward direction of the rupture most of the seismic energy will arrive in a large brief pulse. Backward directivity effects are recorded as long duration motions with low amplitudes at long periods. Considering the aforementioned works, an attempt is made here to explain the effects of rupture directivity using waveforms from earthquakes which occurred in the study area (North Aegean, Figure 1). Digital recordings were taken from the broadband seismological stations belonging to the Hellenic Unified Seismological Network (HUSN, network codes: HL, HT, HP, HA). Waveform data have been processed to form individual events corresponding to the initial earthquakes, and have been associated with the appropriate response information for the time period of the event. The deconvoluted data is shown in ground velocity units. A demonstration of the effect of the ground motion directivity pulses is given in Figure 1 for the Lemnos earthquake (M 5.9). The earthquake occurred on January 8th 2013 in North Aegean Sea on a right lateral strike slip fault. The fault plane solution estimated by NOA (National Observatory of Athens) and it indicates a right lateral strike slip faulting mechanism in a NE-SW direction (strike: 600), moment magnitude of 5.7 and a shallow hypocenter (8 km), at only 42 km epicentral distance from the Lemnos island. The locations of the stations used for this study and the recorded ground motions (north south component) as well as the focal mechanism of the earthquake are presented in Figure 1. The main aspects of the rupture configuration contributing to the generation of fault ground motions pulses during a strike-slip faulting event are studied here. According to the focal mechanism we expect that forward rupture directivity effects propagate along strike. Therefore, stations recordings located in compression (grey) areas will present the forward rupture directivity effect whereas the recordings placed in dilatation (light) areas will show the backward directivity effect. Figure 1 points out the influence of rupture directivity effects at the recording sites. Despite similar epicentral distances, stations located at N and NNW as well as S and SE from the epicenter have amplitudes much larger than those located at E and W. Some representative stations along with the corresponding recordings and their rupture directivity classification are shown in Table 1. For example, the SIGR record is displayed where ground motions have a large amplitude and a short duration (forward directivity effect). On the other hand, the ground motion in station AOS is characterized by a longer duration and a lower amplitude ground motions (backward directivity effect).

ABSTRACT. The dynamics of the Hellenic lithosphere has been extensively studied over the last decades. However, tomographic investigations on the seismic structure of its upper mantle have yielded controversial interpretations, mostly related to restraints due to poor resolution, especially for the intermediate depth range down to 150 km. This study provides new constraints on the intermediate depth, upper-mantle shear velocity structure of Greece using broadband Rayleigh-wave recordings. The analysis is a three-step procedure: acquisition of waveform recordings, dispersion curve estimation, and inversion. The data are constituted of broadband waveforms of over 670 events recorded by ~200 broadband stations of the Hellenic Unified Seismological Network (HUSN; http://www.gein.noa.gr/en/networks/husn) and Kandilli Observatory and Earthquake Research Institute network (KOERI, 2001) between 2010 and 2018. Additional recordings were acquired from stations of the Corinth Rift Laboratory (CRL), operating in Central Greece, as well as of GEOFON and MEDNET. Phase-velocity dispersion curves were derived using a multichannel cross-correlation technique, applying the Automated Surface-Wave Measuring System algorithm (ASWMS; Jin & Gaherty, 2015), based on the Generalized Seismological Data Functionals (GSDF) proposed by Gee & Jordan (1992). In this method, phase delays are measured between all combinations of neighboring stations of the network to avoid systematic biases due to propagation effects, rather than only for pairs that are aligned with the epicenter, within a few degrees of tolerance along a common great circle path; an assumption that greatly reduces the number of quasi-valid measurements. Phase-velocities were determined in terms of apparent and structural velocities, approximated by the application of the Eikonal and Helmholtz equation, respectively. Phase-velocity maps were generated in a grid cell of cell-dimensions 0.2º×0.2º over the period range 30 to 90 s (Fig. 1a). Checkerboard tests yielded adequate horizontal resolution to distinguish anomalies of about 130×130 km² for the obtained tomograms. The phase-velocity maps were then inverted in order to acquire the vertically polarized shear-velocity (VSV) distribution with depth, using the surf96 code (Herrmann, 1994), derived by a Monte-Carlo scheme on perturbations over initial 1-D models, as implemented in the ASWSM suite (Jin, 2015), modified to take into account the region’s crustal structure (CRUST1.0; Laske et al., 2013). The most prevalent features in the phase velocity maps (Fig. 1) are the Hellenic Subduction Zone (HSZ) and the North Anatolia Trench system (NAT), manifested by high and low velocities, respectively. Low velocities along the outer Hellenic Arc at low periods are pertinent to the thick crust and sedimentation along the HSZ (Laske et al., 2013). Fast velocities beneath the Cephalonia-Lefkas-Akarnania Block (CLAB, Fig. 1), considered a microplate (Perouse et al., 2017) are indicative for deep lithospheric roots. A high velocity anomaly extends below the Greek mainland and the South Aegean Active Volcanic Arc (SAAVA), consistently with other tomographic studies (e.g. Papazachos & Nolet, 1997). Cross-sections across the 3-D absolute VSV model (Fig. 2) highlight a low velocity zone hosting intermediate depth seismicity, above a high velocity surrounding upper mantle material deeper than 90 km. This finding is compatible with Spakman & Nolet (1988) and Granet & Trampert (1989), who interpreted a low velocity anomaly at similar depth as representing a possible detachment zone along the slab, and with Suckale et al. (2009) who found a low-velocity layer at the western part of the HSZ at depths 40-90 km, explained as the hydrated crust of the Hellenic slab. The upper mantle of North Aegean is dominated by slow velocities, compatible with mantle wedge, asthenospheric flow and surface magmatism observed throughout the region. The latter observation, also complies with high crustal stress ratio values (Kapetanidis & Kassaras, 2019), indicative of a stable S3 axis, exhibiting extension in a SSW-NNE direction.

ABSTRACT. Greece is the most seismically active country in Europe, with an estimated 50% of Europe’s and 2% of the world’s annual seismic energy being released on major active faults that cross the Greek territory (Bath, 1983). Several strong earthquakes during the last decades have caused serious damage and loss of human lives. With operational short-term earthquake forecasting still being an elusive prospect, Earthquake Early Warning (EEW) is currently one of the most important developing technologies in applied seismology. These systems are focused on acquiring information from the faster seismic phases, including arrival time, peak-to-peak displacement amplitude and, optionally, pulse duration to estimate location and magnitude based on probabilistic and other approaches before the slower but destructive seismic waves arrive. Depending on the density of the seismological network and the latency of waveform data transmission, an operational EEW system can generate and transmit alerts for impending seismic strong motion at target sites of significant importance and inform the authorities, companies or even the public to take specific risk/damage mitigation measures within the short time window between the warning signal and the arrival of the strong shear or surface waves. In the framework of the Hellenic Plate Observing System (HELPOS) research project, the National and Kapodistrian University of Athens has been working on the application of EEW focused in Central Greece. The monitored region includes major active fault systems, such as the Cephalonia-Lefkada Transform Fault Zone (CLTFZ; Stiros et al., 1994; Papadimitriou et al., 2006; Karakostas et al., 2015) and the thrust faults near Zakynthos island (Papadimitriou et al., 2012) in the west, the Andravida fault (Ganas et al., 2009; Papadopoulos et al., 2010) in NW Peloponnese, the Corinth Rift (Bernard et al., 1997; Kapetanidis et al., 2015; Kaviris et al., 2017, 2018), the pull-apart fault system in Lake Trichonis (Kassaras et al., 2014) and, towards the east, the fault systems surrounding the capital, Athens (Papadimitriou et al., 2002), and the fault systems in Atalanti (Pantosti et al., 2001) and Evia rift (Ganas et al., 2016). In this work we present preliminary results of a pilot application using the PRESTo EEW software (Satriano et al., 2011). We incorporate data from seismological stations of the Hellenic Unified Seismological Network (HUSN), along with stations of the local Corinth Rift Laboratory Network (CRLN; Lyon-Caen et al., 2004) installed in the Western Gulf of Corinth (WGoC). The target sites are major cities of central Greece, including Athens, Patras, Aigion, Corinth and Agrinion. However, we chose to use a much broader area, to avoid strong earthquakes that occur outside the true region of interest being mislocated inside the latter and producing false alerts. The playback feature of the EEW software was used to fine-tune the automatic location algorithm of PRESTo and to calibrate the equations used to calculate the magnitude, by employing a large dataset of significant earthquakes recorded during the past years in the study area. We estimated the absolute capacity of the currently available network to detect and locate earthquakes promptly. To this purpose, we also take into account the latency of data transmission, given that waveforms have to be transferred to the central server running the EEW software before being processed. The EEW system works best in areas where the seismological network is dense enough for first arrivals to be picked in at least 4 stations within a reasonable travel-time. During the real-time application we recorded examples of earthquakes in which the EEW system produced its first alert promptly and with adequate precision allowing for a 4 sec time-window before the shear waves arrive at a major target city at a minimum 30 km epicentral distance (e.g. Fig. 1).

ABSTRACT. The essential goal of vulnerability assessment of buildings and other assets to ground shaking is to estimate their expected performance to ground motion. This will in turn affect the life quality and safety of people living or working inside them, being in their vicinity or depending upon their functionality. Seismic vulnerability of assets, i.e. buildings, critical facilities, lifelines etc., is thus defined as the likelihood of damage from future earthquakes. Vulnerability is an integral component of seismic risk assessment (i.e. the probabilistic estimation of economic loss, life loss or injury, downtime and business interruption). Relationships that define vulnerability are typically classified into empirical, analytical or hybrid, according to the type of data and method used for their determination. In most cases researchers emphasize on fragility and vulnerability assessment of standard buildings, given that they are the most common among the elements at risk. For the existing Greek building stock, fragility curves have been proposed from hybrid methodologies (Kappos et al., 2006; Kappos and Panagopoulos, 2010), based on a combination of real observed damage data and analytical models. Karababa and Pomonis (2011) have proposed a set of empirical fragility curves resulting from the 2003 Lefkada earthquake observed damage data. Following, Pomonis et al. (2013) presented a database of observed damage to 29,000 Greek reinforced concrete (RC), unreinforced masonry (URM) and mixed structure buildings compiled from post-earthquake damage surveys carried-out by government authorities and University researchers after four damaging crustal earthquakes (Kalamata 1986, Pyrgos 1993, Aegion 1995 and Lefkada 2003). A successful attempt to categorize the entire country’s building stock in vulnerability classes and for each municipality was performed during the implementation of the research project “Greco-Risks” (Kouskouna et al., 2014). In detail, the structural characteristics of the Greek building stock, derived from the December 2000 Building Census was analyzed, using parameters, such as the construction material, the period of construction and the number of floors. This led to building classification according to the vulnerability classes proposed by the European Macroseismic Scale (EMS-98).. The level of analysis was set to the Kallicratis municipality administrative system. The full combinations resulted in 368 building sub-classes, many of which (79 sub-classes) contain zero or less than 10 buildings (77 sub-classes). To further simplify the analysis, from the seismic risk point of view, the existing buildings can be grouped into: • 3 periods of construction (before 1961, 1961-1995, after 1995 incl. under construction), according to the evolution of the Greek earthquake code (the first compulsory seismic design code of Greece was introduced in March 1959 and the second in January 1995 – although interim guidelines were also developed in 1986 following experiences of the 1981 Corinth Gulf earthquakes of February-March 1981); • 3 classes of height (low-rise i.e. buildings with 1 to 3 floors incl. the ground floor; medium-rise i.e. buildings with 4 to 6 floors incl. the ground floor; and high-rise (i.e. buildings with 7+ floors incl. the ground floor) and • 6 construction material classes (wood, metal, reinforced concrete, stone, brick or concrete block, other materials). This grouping results in 54 seismic vulnerability classes. It is worth noting though that only 12 classes contain 97.8% of the Greek building stock. More than a third of the country’s building stock (34.3%) is in one class, i.e. low-rise reinforced concrete buildings built in 1961-1995. In the framework of the HELPOS project, the National and Kapodistrian University of Athens (NKUA) is carrying out research, based on the above procedure. The results of the vulnerability assessment will be updated by using, after homogenization, the most recent data of the Greek building stock, derived from the February 2011 Building Census which contains 4.053.451 buildings. The data are categorized in 11 periods of construction, 5 height classes (number of floors) and 5 construction material classes. It should be noted that 52.186 buildings “under construction” and 77.263 of “Other” construction material were also enumerated (the class “under construction” will be excluded from the analysis, the class “Other material” warrants further investigation as to its definition, given that it may include highly vulnerable buildings, such as aging adobe or rammed earth buildings). Regarding seismic risk assessment, the buildings will be grouped into 4 periods of construction (before 1961, 1961-1995, 1995-2005 and after 2005, as a new seismic code came into force in 2004), 3 classes of height (low-, medium- and high-rise) and 5 classes of construction material (wood, metal, reinforced concrete, stone, brick or concrete block). The analytical final results of the aforementioned methodology will present the categorization of the Greek building stock and the percentage of vulnerability classes at municipality and prefecture level. An example of this implementation is shown in Figure 1a,b for the Prefecture of Eastern Attica, which includes 13 municipalities. During the period 2001-2008, the area experienced a building boom, which led to an increase of modern buildings, according to the revised Greek seismic design code (2004). A decrease of buildings belonging to the EMS-98 vulnerability classes A, B is observed, which is due to their replacement by new constructions and the increase in the size of the stock. Also, a decrease by about a quarter of the incidence of vulnerability classes C and D, respectively, was more than compensated by the increase of class E, which reached 23%. Further investigation of such results may also reveal possible societal changes. The procedure will be applied to the entire Greek building stock and all the municipalities, with a detailed table of how the census data are mapped to the EMS-98 classes. We expect that the results will show that the country’s present stock consists in large part of better designed and more resistant buildings, while municipalities with aging and vulnerable stock will also be identified.

ABSTRACT. The use of real-time in natural disasters is on the rise. Earthquake real-time applications have proved to be a useful tool for acquiring a rapid estimation of ground shaking immediately after an earthquake occurrence. USGS ShakeMaps (Wald et al., 2005) and PAGER (Wald et al., 2010) applications are two of the most known. In Greece, the Earthquake Planning and Protection Organization – Institute of Engineering Seismology and Earthquake Engineering (EPPO-ITSAK) provides PGA maps for moderate and large earthquakes using the ShakeMaps application within 30 minutes (Wald et al., 2005). In 2015, the National and Kapodistrian University of Athens (NKUA) was the first institution in Greece that developed its own application, in Matlab environment, for creating rapid PGA maps in the case of earthquake occurrence (Kouskouna et al., 2014). This application was further upgraded by Sakkas (2016) and Sakkas et al. (2018), taking into account modern GMPEs for calculating PGA and Peak Ground Rotations – torsion and rocking (PGR) – incorporating, in addition to moment magnitude (Mw), epicentral distance (Repi) and focal depth (h), also the soil type (rock, stiff or soft soil) and focal mechanism type (normal and strike-slip or thrust). The real-time application is hosted by NKUA and publicly available online at http://macroseismology.geol.uoa.gr/realtime/ (the home page is presented in Figure 1). The application presents PGA and PGR maps in a user-friendly environment with google maps as base maps, zoom-in and zoom-out options, as well as activation and deactivation of the PGA and PGR thematic layers. Maps are created in a few seconds in a run-of-the-mill personal computer. The algorithm utilizes the internet, RSS feeds, XML DOM elements, HTML and Matlab mathematical, scripting and plotting capabilities. Within the framework of HELPOS project, NKUA, as official partner, will host both its own application and ShakeMaps (Wald et al., 2005). In this context, we present the Sakkas (2016) and Sakkas et al. (2018) upgrade. The latter incorporates the most recent regional GMPEs for Greece. Specifically, PGA and PGR maps are produced in real-time for both shallow and intermediate depth earthquakes with M≥4.0. More specifically, for shallow earthquakes, five (5) GMPEs (Skarlatoudis et al., 2003; Danciu and Tselentis, 2007; Segou and Voulgaris, 2013; Sakkas, 2016; Chousianitis et al., 2017) are used for the calculation of PGA in different thematic layers. For intermediate depth earthquakes, GMPEs proposed by Skarlatoudis et al. (2013) are applied. For the calculation of PGR, the GMPEs for shallow and intermediate depth earthquakes of Sakkas (2016) and Sakkas et al. (2018) are used. Soil types are based on the 1:500.000 Geotechnical map of Greece and focal mechanism type on Papazachos et al. (1998), Benetatos et al. (2004) and Giardini et al. (2013), taking also in account the interface and in-slab zones proposed in Kkallas et al. (2018). PGA values for all GMPEs adopted in this study are presented in Figure 2. Future development of the algorithm will incorporate real-time PGA measurements from accelerographs and seismographs, belonging to the national infrastructure of the HELPOS project. In addition, residuals of GMPEs compared to observed measurements will be embedded and open-source software and improved mapping capabilities of GIS software will be examined for better representation of PGA and PGR maps.

ABSTRACT. The Gulf of Corinth (GoC) is an active tectonic rift located in central Greece. Its unique seismotectonic properties have rendered it a prime candidate for tectonic (e.g. Bell et al., 2008), seismic (e.g. Stefatos et al., 2002) and seismological (e.g. Rigo et al., 1996) studies. Its long history of both moderate-to-strong events (Makropoulos et al., 2012) and seismic swarms (Kapetanidis et al., 2015; Mesimeri et al., 2016) has been the main instigator for installing and operating dense local networks. The intense observation period of the GoC started in 1995, with the installation of the permanent Cornet seismological network (Papadimitriou et al., 2010) by the Seismological Laboratory of the National and Kapodistrian University of Athens (SL-NKUA). This network was located at the eastern tip of the rift, monitoring an area that featured the destructive Alkyonides sequence of 1981 (Jackson et al., 1982). The four digital stations that comprised Cornet recorded over 6,300 events until 2008. Near the western part of the GoC, the Corinth Rift Laboratory Network (CRLN) was installed in 2000 (Lyon-Caen et al., 2004) to monitor the area surrounding the focus of the 1995 Aigion earthquake (Bernard et al., 1997). The CRLN has since facilitated numerous studies of seismicity in the area, providing local recordings of thousands of events every year. Today, the network is comprised of six borehole and eight surficial stations. The above networks have been complemented by broadband stations operated by the SL-NKUA, the Geodynamic Institute of the National Observatory of Athens (GI-NOA) and the Seismological Laboratory of the University of Patras (SL-UP). In 2008, the Hellenic Unified Seismological Network (HUSN) launched, providing prompt and uninterrupted access to the continuous data recorded by stations of the three institutes. The extensive record of monitoring in the GoC has permitted the detailed study of seismic properties. Shear-wave Splitting (SwS) is the phenomenon of velocity dependence from the propagation direction of shear-waves. The latter undergo splitting and are distinguished into two components; the Sfast travelling with a higher velocity and the Sslow. It is a prominent characteristic of media with strong anisotropic features, such as finely-layered rocks (Valcke et al., 2006). However, it has long been debated that the cause of SwS in the upper crust can be attributed to the existence of vertical microcracks, saturated with fluids. These microcracks are sensitive to both pore-fluid and local stress variations, as described by the Anisotropic Poro-Elasticity (APE) model (Crampin and Zatsepin, 1997; Zatsepin and Crampin, 1997). Thus, the polarization direction of the Sfast (φ) can be used as an indicator of the regional maximum horizontal stress component (σΗmax) and the time-delay between the arrivals of the split waves (td) can be viewed as a representation of the pore stress state. SwS has been studied in the GoC since the 1990s (Bouin et al., 1996). In the current study, we combine results obtained from recordings of Cornet, CLRN and HUSN, to delineate the anisotropic features of the whole GoC. The database constructed in the presented work is composed of 281 events measurements between 1996-1997 from the eastern GoC (Kaviris, 2003; Papadimitriou et al., 1999), 201 measurements from the Villia sequence of 2013 (Kaviris et al., 2014), 663 pairs from events of 2013 (Kaviris et al., 2017) and 1,642 measurements from events of 2014 (Kaviris et al., 2018) in the western GoC. The dataset was further improved by including new measurements from recent events. The mean φ (in most stations) seems to agree with the general WNW-ESE direction of σΗmax, as determined by seismotectonic data in the area (Armijo et al., 1996; Rigo et al., 1996; Bernard et al., 1997; Elias and Briole, 2018). However, there are significant deviations from this direction. A group of stations in the NW edge of the GoC exhibits directions perpendicular to the above, i.e. NE-SW. Time-delays do not exhibit a specific trend, which is an expected feature, given that they are affected by factors with a periodicity far smaller than the length of the database. Clarifying the characteristics of seismic anisotropy in the GoC is pivotal for monitoring stress variations through SwS (Crampin et al., 1999) and constraining focal mechanisms with shear-wave polarizations, after the effect of anisotropy is corrected. The presented detailed report of SwS properties in the whole of the GoC would be impossible without the operation of dense local networks. Splitting studies involve a rigid and strict event selection procedure and an even stricter analysis regime, leading to a significant percentage of rejected candidates. Without the provision of thousands of events, the number of results would be poor, leading to an inconclusive interpretation of the phenomenon. The need of constantly improving and densifying the networks is paramount for such studies. Initiatives, such as the HELlenic Plate Observing System (HELPOS), have enhanced the ability of conducting SwS surveys by expanding data availability and contributing to the operation of the participating networks.

ABSTRACT. Introduction

Urban soil is generally contaminated to a variable degree depending on its proximity to potential contaminating sources. Traffic is one of the main sources of urban contamination, e.g., Pb from the use of leaded petrol, Zn and Cd from tyre wear, Sb from brake pads, and the platinum group elements (PGEs) from the wear of catalytic converters, are some typical elements that often reach high concentrations in the urban environment. Lead was also a key ingredient in white paint, and in towns with a high proportion of white wooden houses very high concentrations were found in soil. Crematoria can or have emitted mercury (Hg). Coal, lignite and heavy oil fired electrical power and heating stations emit S, Ag, V, U, Br and Ba. The use of impregnated wood may have resulted in high concentrations of As, Cr and Cu, especially in kindergartens (nursery schools) and playgrounds. Building materials (plaster and paint) may also contain high concentrations of organic contaminants, especially polychlorinated biphenyls (PCBs), which again end-up in urban soil. Coal and wood burning, the use of diesel fuel, and the production of coke, all lead to the emission of polycyclic aromatic hydrocarbons (PAHs). There exist countless other sources of local contamination in towns, and there is thus every reason to be concerned about the quality of the urban environment, and the suitability of soil for sensitive land uses, such as schools, playgrounds, parks and vegetable gardens. Contaminated urban soil may contaminate indoor dust and, therefore, lead to an increased human exposure to inorganic and organic toxic chemicals. Consequently, the distribution of contaminants in urban soil needs to be documented and made known to city administrations to avoid costly mistakes in land use planning, and further spreading of highly contaminated materials.

Urban geochemistry projects

The Institute of Geology and Mineral Exploration (presently the Hellenic Survey of Geology and Mineral Exploration) realised the significance of carrying out systematic urban geochemical mapping surveys to assist urban authorities and other stakeholders in sustainable land use planning. The first multi-sample media urban survey was carried out in 1989-1992 in Aghios Constaninos (Kamariza) and Lavrion, municipalities to the south-east of Athens, which were centres of mining and smelting activities from ancient to recent times (Hatzigeorgiou-Stavrakis and Vergou-Vichou, 1992). Samples of garden soil (n=187), house dust (n=159) and road dust (n=169) were collected, analysed and studied. The health-related hazards affecting the local population were documented by cross-sectional epidemiological studies.

The second multi-sample media urban geochemical survey was carried out in the Lavrion urban and suburban area (1994-1999), and is considered to be the most comprehensive urban geoscientific project that has ever been carried out, not only in Hellas but globally (Demetriades, 1999; NTUA, 1999). It was a collaborative project between the Institute of Geology and Mineral Exploration and the National Technical University of Athens, and was coordinated by the Municipality of Lavreotiki. Apart from the geochemical results in overburden samples (n=224) and house dust (n=127), different thematic maps were compiled at a scale of 1:5000: (a) metallurgical processing wastes and representative samples (n=62) collected and analysed, (b) parent rocks and representative samples (n=140) collected and analysed, (c) land use, (d) property ownership, and (e) hazard and risk. The geochemistry of the subsurface, and the quality of ground water, were studied by sampling of drill cores and boreholes/wells, respectively. Further, the chemical results of human tissues, such as human blood from 235 children, deciduous teeth (n=82) and 24-hour urine (n=65) showed that the contaminants have entered the human body and affected human health and, especially, of children. The end products were (a) an integrated environmental management plan for the remediation of the different types of metallurgical processing wastes and contaminated overburden, and (b) measures for the protection of the local inhabitants. As multi-sample media urban geochemical surveys are costly, it was decided to carry out in other towns systematic surface soil (0-10 cm) multi-element geochemical surveys using a regular sampling grid of 500x500 m. Six towns have been mapped up to now, and these are (i) Nafplion (Fig. 1a; Vassiliades, 2008a; Tassiou, 2009a), (ii) Sparti (Fig. 1b; Vassiliades, 2008b; Tassiou, 2009b), (iii) Drama (Fig. 1c; Vassiliades, 2008c; Tassiou, 2009c), (iv) Thrakomakedonaes (Fig. 1d; Vassiliades, 2008d; Tassiou, 2009d), (v) Volos (Tassiou and Kaminari, 2016; Tassiou et al., 2016), and (vi) Igoumenitsa (Gerouki and Liakopoulos, 2016; Gerouki and Sgouros, 2016), with the collection of 144, 206, 176, 173, 205 and 135 soil samples, respectively. In order to produce compatible and harmonised urban geochemical databases all samples were analysed by the same hot aqua regia analytical method at the same commercial laboratory.

References Demetriades, A. (Ed.), 1999. Geochemical atlas of the Lavrion urban area for environmental protection and planning. Vol. 1: Explanatory text, 365 p.; Vol. 1A: Figures and Tables, 210 p.; Vol. 1B, Appendix reports, 176 p.; Vol. 2: Geochemical atlas, 199 p.; Vol. 4: Environmental management plan for the rehabilitation of soil in the Lavrion urban area, 155 p. LIFE Programme Contract No: 93/GR/A14/GR/4576, Soil rehabilitation in the Municipality of Lavrion. Open File Report E-8272, Institute of Geology and Mineral Exploration, Athens, Hellas.

(a) (b)

(c) (d) Figure 1. (a) Geochemical distribution maps of Pb in surface soil (0-10 cm) in (a) Nafplion (Vassiliades, 2008a); (b) Sparti (Vassiliades, 2008b); (c) Drama (Vassiliades, 2008c); (d) Thrakomakedhonaes (Vassiliades, 2008d).

Gerouki, F., Liakopoulos, A., 2016. Environmental geochemical study of urban-suburban area of Igoumenitsa. Vol. A: Interpretative text. Open File Report Ε11137, Institute of Geology and Mineral Exploration, Athens, Hellas, 150 p. Gerouki, F., Sgouros, D., 2016. Environmental geochemical study of urban-suburban area of Igoumenitsa. Vol. B: Geochemical maps. Open File Report Ε11138, Institute of Geology and Mineral Exploration, Athens, Hellas, 53 p. Hatzigeorgiou-Stavrakis, P., Vergou-Vichou, K., 1992. Environmental geochemical survey in the area of Lavrion and Aghios Constantinos (Kamariza), Attiki. Open File Report E-6778, Institute of Geology and Mineral Exploration, Athens (in Greek with an English abstract). NTUA, 1999. Environmental characterisation of Lavrion site – Development of remediation techniques. Vol. 3, LIFE Programme Contract No: 93/GR/A14/GR/4576, Soil rehabilitation in the Municipality of Lavrion. National Technical University of Athens, Greece. Open File Report E-8272, Institute of Geology and Mineral Exploration, Athens, Hellas. Tassiou, S., 2009a. Environmental geochemical study of urban-suburban area of Nafplion. Vol. A: Interpretative text. Open File Report Ε10258, Institute of Geology and Mineral Exploration, Athens, Hellas, 123 p. Tassiou, S., 2009b. Environmental geochemical study of urban-suburban area of Sparti. Vol. A: Interpretative text. Open File Report Ε10304, Institute of Geology and Mineral Exploration, Athens, Hellas, 127 p. Tassiou, S., 2009c. Environmental geochemical study of urban-suburban area of Drama. Vol. A: Interpretative text. Open File Report Ε10282, Institute of Geology and Mineral Exploration, Athens, Hellas, 127 p. Tassiou, S., 2009d. Environmental geochemical study of urban-suburban area of Thrakomakedonaes. Vol. A: Interpretative text. Open File Report Ε10230, Institute of Geology and Mineral Exploration, Athens, Hellas, 132 p. Tassiou, S., Kaminari, M., 2016. Environmental geochemical study of urban-suburban area of Volos. Vol. A: Interpretative text. Open File Report Ε11135, Institute of Geology and Mineral Exploration, Athens, Hellas, 257 p. Tassiou, S., Kaminari, M., Sgouros, D., 2016. Environmental geochemical study of urban-suburban area of Volos. Vol. B: Geochemical maps. Open File Report Ε11136, Institute of Geology and Mineral Exploration, Athens, Hellas, 53 p. Vassiliades, E., 2008a. Environmental geochemical study of urban-suburban area of Nafplion. Vol. B: Geochemical maps. Open File Report Ε10257, Institute of Geology and Mineral Exploration, Athens, Hellas, 47 p. Vassiliades, E., 2008b. Environmental geochemical study of urban-suburban area of Sparti. Vol. B: Geochemical maps. Open File Report Ε10303, Institute of Geology and Mineral Exploration, Athens, Hellas, 47 p. Vassiliades, E., 2008c. Environmental geochemical study of urban-suburban area of Drama. Vol. B: Geochemical maps. Open File Report Ε10281, Institute of Geology and Mineral Exploration, Athens, Hellas, 47 p. Vassiliades, E., 2008d. Environmental geochemical study of urban-suburban area of Thrakomakedonaes. Vol. B: Geochemical maps. Open File Report Ε10230, Institute of Geology and Mineral Exploration, Athens, Hellas, 47 p.

ABSTRACT. Recent large sub-salt discoveries in east Mediterranean waters have steered the focus on imaging beneath complex salt structures, where the main challenge is to correctly illuminate the sub-salt section. This involves optimizing acquisition parameters as well as building an accurate subsurface geological model. Only limited regions in the east Mediterranean are covered by multi-azimuth surveys; most of the 3D surveys available are narrow-azimuth. A lack of data diversity degrades the imaging of sub-salt zones even when using accurate subsurface models. Optimal model building for depth imaging involves the application of many complimentary imaging technologies to mitigate assumptions in any singular process. Illumination issues in the east Mediterranean are primarily caused by the complex interaction of shales and salt. The geometry of the salt layer and the velocity contrast across neighbouring lithologies determine the illumination and imaging quality beneath the salt layer. Using accurate interpretation of the top and base salt, and inserting a reliable velocity in the model, enhances the sub-salt imaging. This work focuses on the salt layer model building in three zones across the east Mediterranean Sea and the optimization of the salt/shales, and salt/carbonates velocities to enhance the sub-salt imaging and improve the reliability of amplitude data.

ABSTRACT. The existence of active petroleum systems in Western Greece has been known since the 5th century B.C. (Karakitsios, 2013), when the Keri oil seep was documented by Herodotus in Zakynthos. In more recent times, over 5000km of 2D seismic data have been acquired and over 40 exploratory wells have been drilled in the western Greece onshore area, in search of commercial hydrocarbon accumulations. Success has been limited to date, largely due to the complexity of the shallow geology and surface topography, which results in a poor subsurface seismic image. In 2014, Energean Oil & Gas started a new phase of exploration activities in the area, encouraged by oil discoveries in the Mesozoic carbonates at Katakolon in NW Peloponessos (Greece) and Shpiragu, Ballsh and Cakran in Albania. While these discoveries confirm the hydrocarbon potential of NW Greece, much work is required to enhance our subsurface models and improve our geological understanding of the area. NW Greece lies on the external part of the Dinaride-Hellenide fold and thrust belt, next to the boundary with the Apulian platform. This orogen is traditionally divided in 5 different units: • Pre-Apulian zone, which consists of Triassic to Miocene deposits that characterize the transition zone between the Ionian basin and the Apulian platform. • Ionian basin, characterized by Triassic evaporates, Jurassic to Eocene carbonates with minor shales and Oligocene flysch. • Gavrovo / Kruja zone, which contains shallow water carbonates in the Eocene and Cretaceous. No older formations have been drilled yet or outcrops exist in the area. • Distal Pindos / Crasta-Cukali, which represents the envelope between the Gavrovo zone to the West and the Pelagonian nappe in the East. It contains Mesozoic deep sea sediments and Upper Cretaceous to Eocene flysch. • Pindos unit, characterized by oceanic domain sediments and ophiolitic rocks. Despite the still undergoing discussion on the origin of this unit, it is generally accepted that it was created during the opening of the Pindos Ocean in the Jurassic and obducted during the closure of the Neotethys Ocean (Papanikolaou, 2009). Several structural models have been proposed in the past with significant implications for the deep and shallow prospectivity, since the Filiates-1 well (1966) drilled Cenozoic sediments below Triassic evaporites. One group of authors believe that several imbricates of Ionian basin are detaching one on top of the other with the Triassic evaporites acting as the major detachment in the area (Pieri, 1990). Permian sediments and basement remain unknown due to lack of well penetrations and outcrops. The alternative theory argues that the Ionian basin could be overthrusting the Apulian platform (Velaj, 2015). In this review, we focus on the northernmost part of the Ionian Basin in Greece (figure 1) where four new structural sections have been constructed based on detailed surface geological data, well information and vintage 2D seismic. Our study integrates published and non-published information in order to build a consistent structural model that allows the definition of the major structural elements across the region. Our interpretation (figure 2) is consistent with gravity and magnetic modeling, and also balanced and sequentially restored. This interpretation reflects the clear influence of salt tectonism since the early Jurassic, similar to what has been documented in Albania (Bega et al., 2017). The main processes affecting this restoration are: tectonic loading, erosion, decompaction, flexural isostasy, thermal subsidence and shortening from Oligocene times. The results of this restoration have been used for the construction of a 2D thermal maturity model. This modelling exercise shows that the burial and maturation history of the potential petroleum sources are strongly influenced by the kinematics of the deformation and thus, the onset of expulsion is modelled to become younger towards the West. Despite the high uncertainties that remain in the area, we believe that this work will help to understand the evolution of the Hellenide fold and thrust belt. In the near future, this will be done with the support of new seismic coverage being acquired at present times. References Bega, Z., Soto, J.I., 2017. The Ionian Fold-and-Thrust Belt in Central and Southern Albania: A Petroleum Province With Triassic Evaporites. Permo_Triassic Salt Provinces of Europe, North Africa and the Atlantic Margins. pp 517-538. [Book chapter] Cavazza, W., Wezel, F.C., 2003. The Mediterranean region – a geological primer. Episodes, Vol.26, no.3, pp. 160-168. [Journal Article] Karakitsios, V., 2013. Western Greece and Ionian Sea Petroleum Systems. AAPG Bulletin, v.97, no.9, pp. 1567-1595. [Journal Article] Papanikolaou, D., 2009. Timing of tectonic emplacement of the ophiolites and terrane paleogeography in the Hellenides. Lithos, Vol. 108, pp. 262-280. [Journal Article] Pieri, M., 1990. Structural model of Western Greece (Epiros and Akarnania). Public Petroleum Corporation of Greece. [Dissertation] Velaj, T., 2015. The structural style and hydrocarbon exploration of the subthrust in the Berati Anticlinal Belt, Albania. Journal of Petroleum Exploration and Production Technology, v.5, Issue 2, pp. 123-145 [Journal Article]

ABSTRACT. Introduction Diagenetic processes begin immediately after the deposition of a clastic sediment and continue until the time of anchimetamorphism. All processes are gradual with increasing temperature and pressure. Diagenetic changes depend on the burial depth, the temperature, the chemical composition of the interstitial water and the type of the clastic constituents and cements. The factors that affect the degree of compaction of the components of a clastic sediment are the depth, the size of the grains, the type of clay minerals, the organic matter content, and various geochemical factors. The reduction of porosity and the deposition of cement material restrict the circulation of the fluids, particularly in sandstones, and negatively affect the oil reservoirs. In addition, the burial depth of the sediment is important because it can drastically reduce porosity, especially at depths >5 km (Chamley, 1989; Weaver, 1989; Boggs, 2009).

ABSTRACT. Motivation-Objectives Most carbonate fractured reservoirs show high variation in lithology, diagenesis, fracture intensity, orientation and connectivity. This high degree of heterogeneity can have a significant impact on reservoir quality and sustainability of production. Outcrop analogues are key elements in the understanding of reservoir architecture and heterogeneity (Jones et al., 2015). Subsurface data represent an extremely small fraction of the reservoir complexity, while most times are not being representative for full fracture networks. This fact often leads to misinterpretation of well data and poor reservoir modelling. Outcrop analogue studies can significantly improve the understanding of fracture characteristics and their impact on fluid flow in hydrocarbon reservoirs. Capturing fracture data across multiple scales requires a range of different methods and appropriate technologies (Jones et al., 2015). We applied this strategy combining traditional fieldwork and digital data capture in a pilot study at a key outcrop along the Cretaceous Wasia and Thamama Group contact, in Ras Al-Khaimah (UAE), since these are regionally important fractured reservoirs.

Methods Modern methods of digital acquisition, including terrestrial LiDAR or photogrammetry, are particularly adept at capturing detailed geometrical and geospatial attributes over wide areas. Their main advantage is that they result in more robust datasets over a larger scale-range, particularly for fracture heights, lengths, spacing, clustering, termination and connectivity. The acquired 3D point cloud data were used to extract a very detailed fracture network from the studied outcrop, including fracture orientations and 1D fracture density along two ~ 180 m long scanlines. Additionally, large rock samples were collected along these two scanlines and plug-sized samples were drilled along three orientations orthogonal to each other, with one plug normal to the bedding and two along the bedding and orthogonal to each other (Fig. 1a). The core-plugs were analyzed with the technique of 3D X-Ray Computed Micro-Tomography (μCT). This is a non-destructive technique that allows to acquire images of the interior of the sample, in high resolution and high contrast, allowing to elaborate a 3D reconstruction (Fig. 1b). As in a tomography, numerous sections (e.g. 2000-4200) of the sample are captured in 2D to reconstruct with precision and detail the object in 3D. Moreover, thin sections were made from selected plug samples providing 2D information with a much higher detail in order to examine the microfractures distribution, aperture and filling.

μCT data scan details and processing Standard samples (1.5´diameter x 3´length) were drilled from the outcrop rock samples. The plug-size samples were scanned using Xradia-520 Versa equipment from Zeiss, available with a maximum 160 kV high-energy and micro-focused X-ray tube. The device is equipped with a 2048 x 2048 pixels, noise suppressed, charge coupled detector assembly, having an innovative dual-stage system for getting high contrast images. For all samples, projections between 2651 and 4601 were taken. The distance of source and detector from the sample was chosen to be 73 mm and 50 mm respectively. This resulted in a pixel size (or voxel) of 40.39 microns. After scanning, the data were reconstructed (i.e. create a 3D image using all the 2D radiogram projections) using devices´ included reconstruction software. The plug-size samples obtained from the outcrops had very low porosity, ranging from 0.21 to 3.65%, except for 2 samples that displayed porosity of 7%. Hence, it can be concluded that the fracture porosity plays a major role in these tight carbonates and this was one of the aims of this study. In order to obtain features from the 2D images we chose to apply a simple binary segmentation, by recording the range of pixel intensity values that represent the fractures in all slices of the sample. In order to better visualize the fractures in the 2D slice, a MATLAB code was written to segment the pixel intensity values that represent the fractures and assign those pixels white coloring, while the remaining pixels of the matrix in the slice are given a black color. All the segmented slices were loaded in the Vol-View software (open software), to visualize the segmented slices in 3D. This 3D view showed in great detail the fracture network distribution inside the samples (Fig. 1b).

Core-plug thin sections descriptions Microscopic petrographic analysis showed that most of the rock samples can be classified as mud or grain dominated packstones with forams, echinoderms, bivalve fragments and sporadically Lithocodium-Bacinella green algae. Microstylolites and wispy seams are common, while most of the hairline fractures are straight and have several tip to tip overlapping segments filled often with calcite cement. Few fractures are open or partially filled with silt. Characteristic is that some younger open fractures cross-cut the earlier microstylolitic surfaces (Fig. 1c), while others are developed parallel to the stylolites.

Aperture Width Calculations The aperture width clearly varies along the fractures (Fig. 1d), implying that is meaningless to assign a single aperture value for fractures in reservoir models. Therefore, an aperture width distribution over the 2D slice or along the full sample would be ideal. In this study, we calculated aperture width by measuring the distance normal to the fracture walls; i.e. by measuring the number of pixels lying between the two fracture walls. The full slice aperture distribution is displayed with a color scale in figure 1d and by multiplying the aperture distribution with the micro-CT scan resolution, we can obtain the fracture aperture in μm or mm. In the example of Fig. 1d, representing one of our most fractured samples, the fracture aperture ranges from 0.2-0.6 mm, with a maximum value of around 1.2 mm often located in the overlap zone or relay zone formed between the individual segments.

3D Fracture Intensity Estimating the 3D volumetric fracture intensity (P32) is a quite challenging task and most often is estimated indirectly from the 1D P10 or 2D P21 fracture intensity (Wang, 2005). The 3D fracture intensity (P32) can be expressed as the area of fracture per unit volume of rock mass: fracture density (m-1) = fracture surface area (m2) / sample volume (m3) (Singhal and Gupta, 2010). The fracture surface area is determined by counting the voxels in the complex fracture network in all slices of the sample and multiplying it with the pixel size to get the surface area of the fracture (m2). This surface area is divided by the sample volume (m3) to obtain the fracture density of the sample (units in m-1). The fracture intensities P32 calculated from various scales and resolutions ranges from 0.75-3 m-1 with laser scanning (P10→P32), 9-20 m-1 from field measurements (P10→P32) to 12-35 m-1 (actual average P32 values from μCT data). It is important to note that the P32 fracture intensity obtained by μCT is expected to be much higher than the calculated values from other techniques, since this method is highly sensitive to distinct fracture orientation and size distribution, as well as due to the higher level of detail available in the μCT scan. This is also the underlying reason why it represents a true intensity indicator in the context of DFN modelling.

Conclusions Application of this integrated microstructural methodology in a pilot field outcrop reservoir analogue provides a mean to gain high resolution data, forming a key input in reservoir geo-modelling workflows. The produced digital 3-D analogue, from the outcrop scale down to the core plug and thin section scale, provides essential data for the spatial representation of the reservoir heterogeneities, illustrating the complexity of fractured-carbonate reservoirs. Fracture parameters being quantified across a wide range of scales, and combined with elastic mechanical properties of the carbonate layers represent an ideal basis for the calibration of multi-scale fractured reservoir models.

ABSTRACT. Western Patraikos Block (WPB) was awarded to Hellenic Petroleum in 2012 for Hydrocarbon exploration activities. Extensive geological and geophysical analysis resulted in the identification of multiple potential leads, and one of them is planned to be tested by an exploration well in 2020. As a consequence, several environmental, oceanographic, and geological studies have been conducted in the region in order to ensure negligible impact on the marine environment and safe drilling procedures, namely: 1) side-scan-sonar images and multibeam bathymetry for the identification and mapping of seafloor characteristics (e.g. slope gradients, sedimentary structures), benthic biocommunities, and shipwrecks, cables and other human made objects, 2) analysis of ultra-high-resolution seismic-reflection data (sparker and chirp sub bottom profiles) for the identification and mapping of recent landslides and shallow faults, and 3) examination of a high-resolution 3D PSDM (pre-stack depth migration) seismic cube in order to define lithostratigraphy, fault mapping, and potential drilling hazards in the upper 1000 m of the sedimentary column. This work aims to present the key results from the various studies with ultimate goal to define areas of environmental, archeological, and geohazards risk, which should be treated with caution during drilling activities. The bathymetry of the broader WPG was derived from the PSDM volume (Fig. 1A) and it was complemented by high-resolution (15 m grid) multibeam bathymetric data in selected areas of interest (AOI). Two major morphological settings comprise the WPB. An extensive shelf zone to the east, which represented a delta plain depositional setting during the low sea-level stand (~ 120 m below present sea level) of the last glacial maximum (LGM) (18 – 27 ka B.P.) (Fig. 1A). The lithology of such a depositional setting is anticipated to range from thick (> 1 m), paralic and river sand packages to lagoonal and flooding plain mud deposits. Shallow marine mud deposits characterize this area during high sea-level stands. The transition to the basin floor to the west occurs through a steep (5° - 15° and only locally up to 32°) delta slope (Fig 1D, E). Parallel, continuous to semi-continuous reflections in ultra-high and high-resolution seismic-reflection profiles indicate that mud-dominated sediments characterize late Quaternary deposits on the basin floor (Fig 1C). A deep-tow system (DEEP-TOW 2000, Geoacoustics /Kongsberg), flying 30 m above the seafloor was used in selected areas of interest (AOI) for the acquisition of ultra-high resolution data (side scan sonar and chirp sub bottom profiler), in order to identify and map in detail on the seafloor structures and/or objects with dimensions down to 0.3 m. Through this dataset was possible to examine the presence of benthic biocommunities (e.g. corals), shipwrecks and archeological artifacts, cables, and sedimentary structures (e.g. sediment waves, expulsion features) that might impose issues on safe drilling procedures with respect to the environment. The seafloor in the AOI is smooth in the vast majority of its extension, with no benthic biocommunities or man-made structures and objects. However, the presence of extensive and widespread NW – SE and SW – NE lineations on the side-scan-sonar images reveal intense scouring of the seafloor through intense trawling activity in the area (Fig 1B). Ultra-high resolution seismic-reflection profiles and sediment cores indicate that Holocene (high sea-level stand during the last 10 ka), sediment failures on the delta slope, although common, are of local-scale with limited run off distances (a few hundred meters) with a recurrence time interval of a few to several hundred years. On the other hand, sediment failures and gravity flow deposits during the LGM were abundant and of larger run off (a few to several km). This discrepancy is attributed to the direct river-sourced sediment discharge at the shelf edge during this low sea-level stand, resulting in the formation of thick, loose and easy to fail piles of sediment at a high gradient slope setting. Two large, mass-transport complexes at the southern and northern part of the basin floor are dated to have occurred during the LGM, based on their burial by a 10 – 20 m thick cover of hemipelagic mud. On the contrary, the entrapment of most river-sourced sediments at the shallower parts of the shelf to the east during the Holocene high sea-level stand resulted in lower sedimentation rates at the slope, and thus in more resilient to failure sediment packages. The seismic-reflection profile in Figure 1C, extracted from the available 3D PSDM seismic cube, shows the existence of a major unconformity at the base of the Pliocene – Pleistocene section, which is interpreted to represent the areal exposure of the area during the Messinian Salinity Crisis, during which the sea-level had dropped over 1 km below the present sea level. Clastic sedimentation dominates in the overlying Pliocene – Pleistocene section, which consists of two seismic sequences, named as lower marine sequence (LMS) and upper progradational wedge sequence (UPWS). The LMS consists of continuous to semi-continuous, mid to high-amplitude seismic reflections, and it is interpreted to represent mud-dominated hemipelagic deposits interbedded in places by a few turbiditic channel sand packages. The UPWS comprises several foreset packages in the eastern part of the WPB. Those foreset geometries are interpreted as delta complexes of the Achelous River during low sea-level stands. Foreset packages transit westwards to bottom set packages, these being interpreted to comprise mud-dominated prodeltaic and marine depositional settings. Given the current 3D seismic survey, faulting within the Pliocene – Pleistocene section is not common, and, where present, are of low displacement and occur within deformed strata by Late Neogene diapirism (Fig 1A, C). It is interesting that diapirism has absolutely no surface expression at the eastern part of the WPB, whereas it has a distinct seafloor expression, in the form of elongated bulges, at the western basinal part of the WPB. This discrepancy on the seafloor imprint of the diapiric activity is attributed to much higher sedimentation rates and more efficient burial at the eastern parts of the WPB due to their proximity to the mouth of the Achelous River. Seafloor bulges at the basin floor related to diapirism are commonly characterized by steep flanks (2.5° – 10°), whereas Neogene faulting might also have in places seafloor expression. Ultra-high- and high-resolution seismic-reflection profiles indicate that infrequent (recurrence e period of 100s of years), local-scale (a few to several hundred meters long) failures occur along the flanks of the seafloor bulges formed by the uplifted diapirs at the western part of the WPB. The presence and extension of shallow gas pockets in the Pleistocene section of the WPB was investigated through the generation of amplitude maps from the UPWS. Extremely high amplitude values are commonly associated to the presence of shallow gas accumulations, whose distribution and dimensions can be variable (Fig. 1C, F). In this manner, areas of high probability of encountering shallow gas pockets have been identified and mapped. The presence of (small <10 m in diameter and 1 – 2 m deep), circular depressions above such a zone of amplitude anomalies suggests the development of expulsion features (pockmarks), and thus, supports their interpretation as shallow gas pockets. In conclusion, it is evident that through such a detailed and extensive work the WPB region has been properly evaluated, resulting in the identification and mapping of areas which either for potential geohazards issues (e.g. seafloor gradient, Neogene faults, slope stability, gas pockets), or environmental aspects (benthic biocommunities, shipwrecks, cables) have to be treated with caution and respect.

ABSTRACT. The New Policy Scenarios (NPS), released by the International Energy Association (IEA), which incorporate existing energy policies as well as an assessment of the results likely to stem from the implementation of announced policy intentions, have identified a slight increase, compared to the previous years, to the CO2 emission worldwide. On the other hand, according to the Organisation for Economic Co-operation and Development (OECD) and the IEA report “CO2 Emissions from Fuel Combustion” (IEA, 2018), the CO2 emissions in Greece since 2012 and up to 2016 (last published data) have been decreased from 7000 to 5900 tonnes/cappita. Based on the strategy paper that was published by the European Commission (EC, 2018), the use of carbon capture and storage (CCS) technologies is "still necessary" to achieve long-term climate goals. Taking this into account and the continued high fossil fuel dependency of the Greek power sector, the potential for CCS opportunities within Greece should be investigated as a way of mitigating the greenhouse gases, in line with other options. Different potential sites for CO2 storage have been identified in Greece with total storage capacity in deep saline aquifers and hydrocarbon fields estimated at 2190 Mt. The total effective storage capacity in aquifers alone in Greece was estimated to be around 184 Mt (Hatziyannis, 2009). The aforementioned CO2 storage capacity concerns the Tertiary sedimentary basins of Prinos, West Thessaloniki and a part of the Mesohellenic Trough (Hatziyannis, 2009) (Figure 1). Based on available information, Koukouzas et al. (2009) have conducted a Basin-Scale Assessment (Bachu et al., 2007), identify the best Basin for a potential CO2 storage. The authors concluded that the tectonically stable offshore Prinos Basin has favourable characteristics for CO2 geological storage as well as sufficient storage potential to take in the total amount of CO2 produced by the nearby Komotini gas fired power station (0.7 Mt/year CO2) for several decades. In addition, the offshore location of the potential reservoir and seal units increases the transportation costs but it is countered by the well-established infrastructure framework within 30–40 km of the coast (pipelines, wells and platforms). The onshore Thessaloniki Basin appears to have very good technological and economic potential for CO2 storage. Favourable factors include limited faulting, optimal depth ranges for CO2 storage capacity, and relatively low drilling costs within the closures identified. It appears to have the capability to store all the regional stationary CO2 emissions (one cement plant and one refinery with its 400 MW Combined Cycle Gas Turbine Unit emitting in total around 1.9 Mt CO2/year) or the total lifetime. The CO2 storage potential of the Mesohellenic Trough is unclear due to sparse drilling across the basin although suitable reservoir and seal units appear to be present at appropriate depths, but the extensive faulting should be considered as a potential risk. Tasianas and Koukouzas (2015), have examined further the area for its potential in storing CO2. According to their research, CO2 storage can take place in the Pentalofos sandstone (Figure 2), a reservoir extending throughout the entire MT and it is located below the Tsotylli Formation (Fm) caprock (Zelilidis et al. 2002). More specifically, the geological modelling conducted in the Mesohellenic Trough, allowed the assessment of the CO2 storage potential and provided an estimation of the CO2 storage capacity for the Pentalofos reservoir. The Pentalofos formation is also capped by an effective cap rock, the Tsotylli Formation, and can be, thus, potentially be used as a storage area for CO2 regionally. According to the geological model, the deepest point where the CO2 can be stored corresponds to the base of the Tsarnos formation, at 2544 m depth. The estimated amount of potential CO2 storage is up to 1435 Gt. In addition to the geological modelling, geochemical experiments and modelling were also conducted for the Mesohellenic Trough, which support the fact that Pentalofos and Tsotyli sandstone formations are suitable for the long-term storage of CO2 produced in the neighbouring lignite-fired power plants, at least in terms of mineralogy and geochemistry. To conclude, the large-scale implementation of CCS at large point sources of CO2 in Greece would reduce the national CO2 emissions by 25–28%. The geological settings of the Tertiary and Neogene-Quaternary sedimentary basins in Greece appear to provide a promising option for CCS implementation. The identified potential reservoirs and overlying seal units occur within approximately 100 km of the significant stationary CO2 emissions in NW Greece, which is favourable in terms of infrastructure costs. Continued optimisation of the models used, combined with more information on the structural properties of the potential reservoirs of the sedimentary basins, could help in their further evaluation as a potential storage structures for CO2.

References International energy Association (IEA), 2018. CO2 Emissions from Fuel Combustion 2018, IEA, Paris European Commission (EC), 2018. A Clean Planet for all A European strategic long-term vision for a prosperous, modern, competitive and climate neutral economy, Brussels, Belgium. Hatziyannis, G., 2009. Country updates: Greece. In: Vangkilde-Pedersen T, editor. WP2 Report –Storage capacity. EU GeoCapacity –Assessing European Capacity for Geological storage of Carbon Dioxide. Project no. SE6-518318., 144-147 Koukouzas, N., Ziogou, F., Gemeni, F., 2009. Preliminary assessment of CO2 geological storage opportunities in Greece. International Journal of Greenhouse Gas Control, 3, 502–513. Koukouzas, N., Kypritidou, Z., Purser, G., Rochelle, C.A., Vasilatos, C., Tsoukalas, N., 2018. Assessment of the impact of CO2 storage in sandstone formations by experimental studies and geochemical modeling: The case of the Mesohellenic Trough, NW Greece. International Journal of Greenhouse Gas Control, 71, 116-132. Tasianas, A., Koukouzas, N., 2015. Assessing the Potential of the Mesohellenic Trough and Other Sites,in Greece, for CO2 Storage. World Multidisciplinary Earth Sciences Symposium (WMESS2015), Procedia Earth and Planetary Science, 15, 607 – 612 Zelilidis, A., Piper, D.J.W., Kontopoulos, N., 2002. Sedimentation and basin evolution of the Oligocene-Miocene Mesohellenic basin, Greece. Aapg Bull, 86, 161-182.

ABSTRACT. CO2 injection and storage in deep geological formations can contribute to the exploitation of geothermal potential. Several proposals for the use of CO2 in the exploitation of geothermal energy have been suggested, but still remain at the early research level: (a) use of supercritical CO2 as the working fluid in Enhanced Geothermal Systems (EGS), (b) injection of supercritical CO2 into a deep saline aquifer and formation of a "CO2 Plume Geothermal (CPG) system", that is heated by the naturally increased underground thermal energy within the reservoir, thus providing energy utilization, (c) a hybrid two-stage, integrated, energy recovery approach (initially brine and later brine and CO2) from a deep saline aquifer, (d) use of CO2 as both a pressure-support and working fluid to generate artesian pressures for CO2 and brine production, using both fluids as working fluids and improving the economic viability of geothermal energy production in sedimentary formations, (e) CO2 dissolution in the brine of the reservoir and energy recovery of CO2-enriched hot brine in a geothermal doublet. Regarding the CO2 geological storage in Greece, some potential sites have been recommended. Among them, the case of the Thessaloniki basin is more interested and requires further study.

ABSTRACT. Any geodynamic model for the opening of the western Mediterranean should account for the exhumation and emplacement of the largest outcrops worldwide of subcontinental lithospheric mantle (SCLM) peridotites —and associated UHP eclogites— occurring in the western peri-Mediterranean Alpine chain. It must also explain the origin of the characteristic internal tectono-magmatic zoning of Betic-Rif-Tell orogenic peridotites, recording a polyphase P-T-t evolution from UHP cratonic-like SLCM to hyper-extended, oceanic-like mantle. Here, I present a model for the opening of the western Mediterranean largely segmented by inherited structures from the Mesozoic Paleo-Tethys Ocean. Late Cretaceous to Eocene N-directed subduction of the Tethys and subsequent continental collision occurred in a highly segmented subduction zone where the westernmost segments developed high-T UHP eclogites that did not occur in colder subduction eastern segments. The opening of the Ligurian-Provencal basin and the counter-clockwise rotation of the easternmost Sardinia-Corsica segment followed this contractional event. The easternmost Kabylian-Rif-Betic segment, however, underwent a SSE-directed pervasive back-arc extension during slab rollback leading to the final collision with the African margin. This model provides a common origin and accounts for the internal tectono-metamorphic evolution of orogenic peridotites in the Tell and Betics-Rif belts, and explains the high-T and UHP nature of associated eclogites.

ABSTRACT. The initial concept and recognition in outcrop of a “petrologic moho” was established within the Vourinos ophiolitic complex of northern Greece (Jackson et al 1974). Follow-up work documented the contact between mantle tectonite and an ultramafic-mafic cumulate suite as one of an intrusional topography (Rassios 1981; Harkins et al 1980). The orientation of the petrologic moho and that of stratotectonic “upping” (based on magmatic layering and fractionation patterns) was observed to be at nearly a 90° rotation to that of the dominant lithospheric mantle -> magmatic -> oceanic sedimentary profile. While early research by the aforementioned investigators documented ductile and magmatic structural fabrics in great detail, the block rotation of the petrologic moho unit was assumed to be via a non-exposed Tertiary (?) brittle fault system. Such a fault system was not observed even during detailed explorationist investigation of the area during the 1980’s and 1990’s.

A synthesis of this early research within a modern framework of ductile lithospheric deformation reveals a fabric continuity that suggests this rotation occurred in near-ridge crest ductile conditions. Evidence towards this interpretation includes: -- Continuity of ductile mineral fabric (lineation and foliation) within the magmatic and restite tectonite peridotite within the petrologic moho section and between the petrologic moho section and regional mantle tectonite. -- Parallel orientation of sub solidus mineral enlargement between exposures within the neighboring sub-moho Aetoraches chrome mine and cumulus grains within the magmatic section of the petrologic moho area.

The mechanism of this rotational deformation could be ascribed to proto-transform era tectonism (Garya 2012) or complex deformation within transtensional-transpressional zones between transfer faults (Dewey et al 1998). Within the petrologic moho section, (i) Several fragments of flaser gabbro were observed in the 1970’s research in contact with the north west border of the magmatic section of the petrologic moho area. Today we recognize these could mark the trace of a high temperature (transform) fault; (ii) the cumulate rocks of the petrologic moho section trace magmatic evolution towards troctolite rather than gabbronorite as elsewhere at Vourinos (Rassios 1981). This, in a modern consensus framework, could also be a transform-related phenomenon; (iii) Vourinos is dominated by Cr-rich chromite and chrome ores. The only occurrence of Al-rich chrome ores within the Vourinos mantle section crop out within the nearby Kissavos locality. These Al-rich ores might be related to transform fault-related hydrous magmatic activity concurrent to sub-ridge crest crystallization.

The direct observation of oceanic transform fault systems is difficult: oceanic topographic maps of the “google earth” type show a thick network of such faults at ridge crests, directly implying the coexistence of active ridge crest lithospheric generation with transform fault initiation. Rare instances of transform faults have been documented from ophiolites (eg Troodos-Cyprus, Domokos-Greece) that cut through various lithospheric levels. We believe that at Vourinos, the rotation in ductile conditions of a block of approximately 3 km3 is probably associated with this early ridge crest – transform era. If so, this shows the possible nature of the initiation of transforms at depths about 10km below the ridge crest system.

REFERENCES Dewey J, Holdsworth R, and Strachan R,. Transpression and transtension zones. Geological Society, London, Special Publications 1998, v.135; p1-14. Gerya, T. (2012) Origin and models of oceanic transform faults. Tectonophys., 522-523, 34-56. Harkins, M., Green, H., and Moores, E., 1980. Multiple intrusive events documented from the Vourinos ophiolite complex, northern Greece. Am. Journ. Sci. 280-A, 284-290. Jackson, E.D., Green, H.W., and Moores, E.M., 1975, The Vourinos ophiolite, Greece: cyclic units of lineated cumulates overlying harzburgite tectonite: Bulletin of the Geological Society of America, v. 86, p. 390–398. Rassios, A., 1981. Geology and Evolution of the Vourinos Complex, Northern Greece. PhD. Thesis, Univ. of Calif. (Davis), 499 pp.

ABSTRACT. The United Arab Emirates (UAE)-Oman ophiolite, a thrust sheet of Tethyan oceanic lithosphere that was emplaced onto the formerly passive continental margin of Arabia, is the largest and most well studied ophiolite with excellent preservation of the ocean plate stratigraphy of the obducted oceanic crust with related igneous and metamorphic rocks (Goodenough et al., 2014). Thus, the area provides a wonderful natural laboratory to study the subduction-obduction and their related processes in the mantle wedge at a convergent boundary (e.g., Searle and Cox, 2002; Rioux et al., 2013; Goodenough et al., 2014; Spencer et al., 2017; Joun et al., 2018). The UAE ophiolite belt preserves large slices of complete ocean plate stratigraphic section from mantle, lower crust, sheeted dikes, and pillow lavas of mid-ocean ridge basalt affinity, namely phase 1 magmatism, with intercalated pelagic sediments lying on top of the fault bounded metamorphic sole (Nicolas et al., 2000). This earlier oceanic crust is intruded by phase 2 magmatic rocks that consist of high-level gabbro, dolerite, basalt, pyroxenite, wehrlite and tonalite (Goodenough et al., 2014) with hydrous SSZ geochemical affinity (e.g., Rioux et al., 2013; Haase et al., 2016). Isotopic ages suggest that both magmatic activities are overlapped in the range of ca. 98.6 to 94.5 Ma (Rioux et al., 2016; Joun et al., 2018). These age spans are younger than about 5 Ma from the oldest age of the ophiolite. Apart from the magmatic history that formed the ophiolite crust, the obduction and exhumation history of the Semail ophiolite has been studied by various workers based on the nature of HP-metamorphism beneath the ophiolite complex (Searle and Cox, 2002; Styles et al., 2006). They reported a relatively wide range of ages from ca. 96 Ma (U-Pb ages, Rioux et al., 2016), ca. 92.4 – 94.9 Ma (Ar-Ar ages, Hacker and Gnos, 1997), ca. 89 – 101 Ma (K-Ar ages, Gnos and Peters, 1993). These ages are older than about 6 Ma compared with the youngest estimated ophiolite obduction age of ca. 93 to 83 Ma (Jacobs et al., 2015). These ages were suggestive of a subducting plate origin with crustal slices stacked below the overriding plate during the obduction (e.g. Searle et al., 2015). However, we have reported the weighted mean age of ca. 91.8 Ma from the garnet metagabbro in Masafi metamorphic sole that is ca. 3 Ma younger to the protolith ages of ca. 94.5 and 94.9 Ma which are inferred from the oscillatory zoned zircons (Rioux et al., 2013), and is overlapped with previously reported metamorphic ages from the UAE ophiolite belt (Styles et al., 2006; Searle et al., 2015). The U/Pb ratios yield protolith ages of ca. 93.6 Ma for the olivine websterite sample and ca. 90.6 and 91.2 Ma for the tonalite samples. The same grains for the garnet metagabbro, phase 2 tonalite, and olivine websterite yield all positive εHf(t) values range from 5.6 – 10.0 for the ages 89 – 96 Ma, 5.1 – 10.0 for the age of 87 – 92 Ma, and 12.6 – 22.6 for the age of 89 – 96 Ma. These results indicate that the garnet metagabbro from this study originated from the mantle wedge, thus the overriding plate, formed through the metasomatism of depleted mantle with fluid derived from the subducting plate, rather than the subducted slab that has been interpreted as the origin of garnet amphibolite in general, although the positive εHf value of the tonalite indicates the interaction during this mantle metasomatism as indicated by earlier research (Joun et al., 2018).

ABSTRACT. The Mirdita ophiolites in northern Albania are divided into the Western Mirdita Ophiolite (WMO), with MORB geochemical affinities, and the Eastern Mirdita Ophiolite (EMO), for which suprasubduction geochemical affinities have been reported (Beccaluva et al., 2005). Ultramafic massifs in the WMO are often plagioclase bearing lherzolites/harzburgites whereas those in the EMO are strongly depleted spinel harzburgites.The Tropoje ultramafic-mafic complex, which forms the northernmost part of the EMO, consists of spinel harzburgites, dunites, wherlites, orthopyroxenites and gabbros . The spinel harzburgites, which experienced variable degrees of serpentinization, are coarse- to medium-grained. One of the most striking features of the Tropoje ultramafic rocks is an outcrop of exceptionally fresh coarse- to medium-grained spinel harzburgites. While occasionally the peridotites exhibit a weak foliation, the prevalent texture is protogranular. Olivine is mainly coarse-grained (upto 6 mm size), typically showing kink-bands that frequently contain submicron-sized spinel exsolution lamellae. Both orthopyroxene and clinopyroxene, with grain size up to 3 mm and 1.5 mm, respectively, carry very thin exsolution lamellae of the other pyroxene. Spinel, up to 1 mm in size, is interstitial between boundaries of theassociated silicates.The mineral compositions of the spinel harzburgites indicate that they are strongly depleted in basaltic components. The rock-forming minerals (olivine, orthopyroxene and clinopyroxene) are all highly magnesian and chemically homogenous. The magnesium numbers (Mg#=100xMg/[Mg+Fe]) for olivine and orthopyroxene are fairly homogeneous and vary within the narrow range of 90.9-91.6 and 91.5-91.7, respectively. The clinopyroxene is exceptionally highly magnesian, with Mg# ranging between 93.6 and 95.4. In both orthopyroxene and clinopyroxene, the Al2O3 contents range from 0.95 to 1.75 and from 0.62 to 2.27 wt%, respectively. Spinel shows a considerable variation in Al2O3and Cr2O3. The range in Cr# (Cr#=100xCr/[Cr+Al]) is 51.7-69.2, but nocompositional variations have been observed between core and rim. The silicate minerals are strongly depleted in trace elements. LA-ICP-MS analyses of clinopyroxenes show that the LREE are below detection limit whereas the ratio of (Tb/Yb)N range from 0.10 to 0.15 and Lu is around 0.5xPM.Equilibrium temperatures calculated at a pressure of 1.5 GPa are relatively low, ranging between 620 and 830◦C.The lowest temperature corresponds to the most residual peridotite, in which the clinopyroxene has the highest Mg# (95.4) and the spinel the highest Cr# (69.2).The spinel-harzburgites from these exceptional fresch outcrop have experienced high degrees of partial melting. Applying the method of Hellebrand (2001) to samples containing spinel with Cr# < 60 yields around 20% partial melting.The overall strong depletion in trace elements and prominent depletion of the LREE in clinopyroxenes as well as the absence of hydrous phases is not consistent with a suprasubduction origin as it has been suggested for the Tropoje ultramafic massif.

References Beccaluva, L., Coltorti M., Saccani, E., Sienna, F., 2005. Magma generation and crustal accretion as evidenced by suprasubduction ophiolites of the Albanide-Hellenide Subpelagonian Zone. The Island Arc 14,551-563. Hellebrand, E., Snow, J.E., Dick, H.J.B. Hofmann, A.W. 2001. Coupled major and trace elements as indicators of the extent of melting in mid-ocean-ridge peridotites. Nature, 410, 677-681.

ABSTRACT. Abstract text Cumulate wehrlites, ultramafic lavas, and associated mafic dykes and pillow-lavas outcrop within a Middle-Late Triassic igneous and sedimentary sequence in Othris, Central Greece. These rocks have been variably affected by metasomatic and metamorphic processes (Figure 1). Ultramafic rocks (wehrlites and ultramafic lavas) are serpentinized in processes that are restricted (moderate alteration) or pervasive, forming serpentinites. Balanced lizardite/antigorite ratios suggest that serpentinization took place under conditions that reached greenschist facies. Most trace element concentrations were relatively decreased during serpentinization. Local rodingitization is characterized by the formation of hydrogarnets, secondary diopside, chlorite, pumpellyite and prehnite. This metasomatic mineral assemblage replaced cumulus clinopyroxene as well as primary accessory plagioclase. Rodingitization occurred with diffusive mass transfer of CaOH+ species under relatively mildly oxidizing physicochemical conditions, along with fluid solutions with an increased CO2/H2O ratio. Rodingites formed as a result of extensive metasomatism that replaced protolithic boninitic dykes intruding wehrlites. The metasomatic hydrous fluids responsible for this process were relatively alkaline, occurring under low to moderate P-T conditions (180-320 °C, P≈2-5 kbar), in conditions of increased fO2. Rodingites experienced desilification, and rodingitization also resulted in variable decreases and less often increases in trace element concentration. Carbonation processes affected ultramafic lavas; the most intense carbonation is exposed in the Neraida locality where it has created “layer-cake” structures within the lavas. Metasomatic carbonation was caused by shallow-level continuous circulation of Ca-rich fluids too low in temperature to significantly affect clinopyroxenes. The restricted occurrence of serpentine and hydroandradite indicates that carbonation occurred in association with low-grade serpentinization and rodingitization processes. The metasomatic phenomena documented herein are related to subduction settings and more specifically to the seafloor exhumation of the mafic–ultramafic rocks in the fore-arc area. We have calculated that serpentinization and rodingitization of wehrlites began within relatively moderate temperature and pressure conditions (~350 °C, P≈6 kbar), with rodingitization processes in both wehrlites and rodingites progressing during further continuous cooling of circulating hydrothermal fluids at shallower depths. The final metasomatic stage is represented by carbonation processes.

References

Koutsovitis, P., Magganas, A., Ntaflos, T., Koukouzas N. 2018. Rodingitization and carbonation, associated with serpentinization of Triassic ultramafic cumulates and lavas in Othris, Greece. Lithos, 320-321, 35-48.

ABSTRACT. 1. Background

In Kimi region (Evia island, Greece) the Maestrichtian-Paleocene flysch is composed by sedimentary rocks (sandstones, shales, cherts), intercalations of Upper Cretaceous limestone (Robertson, 1990), as well as olistostromes of serpentinized peridotites. The ultramafics are strongly associated with rodingite dykes, ophicalcites and talc schists. Rodingites appear as veins with horizontal (E-W) or NNE-SSW direction. They are composed by three distinct concentric zones, characterized by specific mineral assemblages. The ultramafic host rocks consist of two thin irregular zones of successive metasomatized serpentinite and chloritite near the contact with the rodingite dykes.

2. Aims and Objectives

The present study aims to investigate the relation between serpentinization and rodingitization, as well as the physicochemical conditions under which Ca-metasomatism affected the exhumed mantle rocks of Kimi. For the purpose of this study the following methods were followed: a) Field work emphasized on the ophiolitic ultramafic rocks intruded by rodingite dykes. b) Mineralogical analyses c) Whole rock chemical analyses d) Stable O-C isotopic analyses of calcite e) Data processing.

3. Results

Petrographical and geochemical investigation of the rodingite rocks included the study of their marginal, transitional and core zones. As calcite occurs in some of the studied samples, rodingites were further divided into two groups, corresponding to non-carbonated (Group-I) and carbonated (Group-II) dykes. Their texture ranges from cryptocrystalline to microcrystalline, usually porphyroblastic including idiomorphic (hydro)garnet and vesuvianite porphyroblasts. In both rodingite groups, chlorite and/or diopside predominate in the marginal zones, whereas vesuvianite and/or garnet are the main mineral phases of the core zones. Tranistional zones include all the aforementioned minerals in various and unequal amounts. Accessory minerals include relict spinel, prehnite, epidote, apatite, allanite, amphibole, dolomite, quartz and opaque Fe-Ti oxides.

Calcite appears in the form of veins or within cavities in the rodingite groundmass. Garnet is mainly classified as (hydro)grossular, whereas a few (hydro)andradite crystals also occur. Chlorite is classified mostly as penninite, whereas clinopyroxene is classified as diopside. Ultramafic rocks are divided into serpentinized peridotites, metasomatized serpentinites and chloritites. Serpentinitic rocks include mostly serpentinite, bastite grains, garnet porphyroblasts, as well as relict pyroxene grains with accessory spinel. Regarding their whole rock chemistry, rodingites are mainly CaO enriched and depleted in SiO2 and total alkalies, whereas their LOI contents are quite high. The carbonated rodingites (Group-II) show significant enrichment in light rare earth elements (LREE). Stable isotopic data in calcite crystals of the rodingite, ophicalcite and red mudstone samples present a wide range of δ13C and δ18Ο VPDB contents. Metasomatized serpentinites show higher CaO and SiO2 contents compared to those of chloritites.

3. Discussion and Conclusions

Rodingitization is strongly associated with serpentinization, evolved under alkaline conditions, in a Supra Subduction Zone (SSZ) within the closing oceanic basin (Robertson, 1990). The occurrence of three distinct zones within the rodingite dykes corresponds to gradual fluid infiltration with H2O/rock ratio and CO2/H2O ratio increasing, and T decreasing towards their cores. Ultramafics are characterized by a transition from an outer metasomatized zone to an inner chlorititic rim near the contact with the rodingite dykes. Rodingitization likely evolved into two metasomatic events characterized by different XCO2 conditions. Vesuvianite was formed at a late stage of the first metasomatic event under Ca2+/OH- rich fluids and low CO2/H2O ratio (Hatzipanagiotou et al., 2003; Li et al., 2004; Li et al., 2008; Koutsovitis et al., 2013). The occurrence of additional calcite in some the rodingite dykes corresponds to a second metasomatic event of higher XCO2 conditions. The CaO enrichment and SiO2-alkali depletion is associated with clinopyroxene and anorthite breakdown dissolution during serpentinization (Frost et al., 2008). LREE enrichment is significantly higher in carbonated rodingites, indicating the presence of carbonic-LREE complexes in the metasomatic fluids, whereas Zr mobility can be associated with the presence of PO43--LREE and LREE-OH- complexes (Aja et al., 1995; Veyland et al., 2000). REE are hosted within monazite and allanite. Stable isotope data indicate the participation of hydrothermal and seawater fluids. The closure of the oceanic basin is accompanied by the formation of Kimi flysch and the incorporation of the ultramafic olistostromes.

4. References

Aja, S.U.,Wood, S.A., Williams-Jones, A.E., 1995. The aqueous geochemistry and the solubility of some Zr-bearing minerals. Applied Geochemistry, 10, 603–620.

Frost, B.R., Beard, J.S., McCaig, A., Condliffe, E., 2008. The formation of micro-rodingites from IODP hole U1309D: key to understanding the process of serpentinization. Journal of Petrology, 49, 1579–1588.

Hatzipanagiotou, K., Tsikouras, B., Migiros, G., Gartzos, E., Serelis, K., 2003. Origin of rodingites in ultramafic rocks from Lesvos island (NE Aegean, Greece). Ofioliti, 28, 13–23.

Koutsovitis, P., Magganas, A., Pomonis, P., Ntaflos, T., 2013. Subduction-related rodingites from East Othris, Greece: Mineral reactions and physicochemical conditions of formation, Lithos, 172-173, 139-157.

Li, X.P., Rahn, M., Bucher, K., 2004. Metamorphic Processes in Rodingites of the Zermatt-Saas Ophiolites, International Geology Review, 46, 28–51.

Li, X.P., Rahn, M., Bucher, K., 2008. Eclogite facies metarodingites: phase relations in the system SiO2–Al2O3–Fe2O3–FeO–MgO–CaO–CO2–H2O: an example from the Zermatt-Saas ophiolite, Journal of metamorphic Geology, 26, 347–364.

Robertson, A.H.F., 1990. Late Cretaceous oceanic crust and Early Tertiary foreland basin development, Euboea, Eastern Greece. Terra Nova, 2, (4), 333-339.

Tsikouras, B., Karipi, S., Rigopoulos, I., Perraki, M., Pomonis, P., Hatzipanagiotou, K., 2009. Geochemical processes and petrogenetic evolution of rodingite dykes in the ophiolite complex of Othrys (Central Greece). Lithos, 113, 540–554.

Veyland, A.,Dupont, L., Rimbault, J., Pierrard, J.-C., Aplincourt, M., 2000. Aqueous Chemistry of Zirconium (IV) in Carbonate Media. Helvetica Chimica Acta, 80, 414–427.

ABSTRACT. Greece is located in the eastern end of Europe where a variety of geological procedures take place such as the Alpine orogenesis. The creation of the Alpine mountain chain, which is one of the most important geological features, is caused by the collision between Europe and Africa. Furthermore, the intense deformation observed in Greece and surrounding areas produces significant seismicity concentrated along active seismic zones such as the Hellenic Arc and the North Anatolian fault (Papazachos et al., 2000). In addition, the gulfs of Corinth, Evoikos and Saronikos also present important seismic activity. Since 2018, more than 10,000 events have been recorded by stations of the Hellenic Unified Seismological Network (HUSN; Papanastassiou, 2011) and were analyzed by the Seismological Laboratory of the National and Kapodistrian University of Athens. Recently, data from the Hellenic Strong Motion Network (HSMN; Theodulidis et al. 2004) were included in the framework of HELPOS project. The “scolv” tool of the SeisComP3 software was used in order to manually revise the automatically located events. The initial catalogue was further enriched with events that weren’t automatically detected, by extracting waveform data according to an initial origin time after visual inspection of the 24-hour recordings on reference stations. In the present study we mainly focus on significant seismic activity that occurred during 2018-2019. In North Aegean, shallow aftershock activity associated with the earthquakes that occurred on the 6th February and 12th of June 2017, in the broader area of Lesvos Island, is still present in 2018. More than 200 events since June, manually analyzed, were used to obtain an optimized local velocity model. The newly developed seismic catalogue revealed distinct spatial ~E-W oriented seismic clusters, compatible with the strike of Quaternary faults in the area south-west of Canakkale and along the southern coasts of Lesvos Island, related to Lesvos-Psara pull-apart basins (e.g. Kiratzi, 2014). In Central Greece, the greatest part of the seismicity is located in the southern termination of Saronikos gulf and in Attica area. The seismic activity in Saronikos gulf is concentrated around Leuces islands, north of Aegina and Methana in E-W striking neotectonic fault zones. In addition, a swarm located along the Poros Fault System (PFS) took place in 2016-2017. In Attica area a microseismic activity occurred in January 2018, north of Mt Penteli (Kaviris et al., 2018), Marathon Bay, Thriassion fault and its continuation in Athens basin. 450 events were located in the vicinity of Attica during 2018-2019 with magnitudes mainly between 1.8 and 2.6. Sporadic seismicity was also detected along the southern shores of Attica. The most notable events of this region occurred on 18 January 2018 (ML=4.2) and 1 May 2018, in the areas NNE of Mt Penteli and Oropos, respectively. The earthquake activity in the broader area of Santorini volcanic center is strongly connected with the tectonic regime, as well as with the volcanic process (Bohnhoff et al., 2006; Dimitriadis et al., 2010; Papadimitriou et al., 2015). The highest rate of seismic activity in this area has been observed along the NE-SW striking Santorini-Columbo volcano-tectonic line, a deep-seated, strike-slip feature (Bohnhoff et al., 2006; Sakellariou et al., 2013; Nomikou et al., 2018). Within this zone, the submarine Columbo volcano exhibits strong seismic and hydrothermal activity which could be linked to the magma reservoir and therefore to the migration of magma and fluids towards the surface (Bohnhoff et al., 2006; Sigurdsson et al., 2006). A similar pattern of seismic activity is observed NE of Columbo, with small-scaled activity spots that might represent local pathways of upward migrating fluids or even developing volcanic activity within this zone of crustal weakness (Bohnhoff et al. 2006). The majority of the recorded seismic activity was located 38.2 km NE of Thira, SSW of Amorgos (Mw=4.5). This cluster lies on the southern boundary of the activated fault during the 1956 tsunamigenic M7.2 earthquake of Amorgos. Another significant portion of the seismic activity (13-14/01/2019) was located south of Akrotirion, 17.1 km SSW of Thira, aligned in a general WSW-ENE direction. The most notable event of this group occurred on 13 January 2019 (ML=3.6). On October 25th, 2018 (22:54 GMT), an M6.8 earthquake occurred 57.0 km SW of Zakynthos Island, at a focal depth of ~11km. The mainshock was widely felt to the island and in many areas of Central Greece. More than 4,000 aftershocks were manually located. A local 1-D velocity model was developed upon a selected dataset (1,000 earthquakes). The aftershock locations reveal a complex hypocentral distribution, which indicates the activation of more than one structure in the area, with five main spatial groups being identified: one situated in the area around the mainshock; another likely associated with the southern prolongation of Cephalonia Transform Fault (CTF) WNW of Zakynthos (Papadimitriou et al., 2006; 2012); a third ~20km to the NNE of the mainshock; a forth in Laganas bay (Southern Zakynthos) and a fifth close to Strofades islands, where the 1997 M6.6 earthquake took place. The obtained results highlight a complex fault pattern in Southern Ionian Sea, as a result of the intense deformation of the overriding crust. Acknowledgements We acknowledge support of this study by the project “HELPOS – Hellenic Plate Observing System” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

References Dimitriadis, I. et al., 2010. P and S velocity structures of the Santorini-Colombo volcanic system (Aegean Sea, Greece) obtained by non-linear inversion of travel times and its tectonic implications. J. Volcanol. Geotherm. Res. 195 (1), 13–30 Kaviris, G., Spingos, I., Millas, C., Kapetanidis, V., Fountoulakis, I., Papadimitriou, P., Voulgaris, N., Drakatos, G., 2018. Effects of the January 2018 seismic sequence on shear-wave splitting in the upper crust of Marathon (NE Attica, Greece). Phys. Earth Planet. Inter. 285, 45–58. Kiratzi, A., 2014. Mechanisms of Earthquakes in Aegean, Encyclopedia of Earthquake Engineering, 1-22, Springer Berlin Heidelberg, DOI: 10.1007/978-3-642-36197-5_299-1 Nomikou, P. et al., 2018. Expanding extension, subsidence and lateral segmentation within the Santorini - Amorgos basins during Quaternary: Implications for the 1956 Amorgos events, central - south Aegean Sea, Greece. Tectonophysics 722:138-153, DOI: 10.1016/j.tecto.2017.10.016. Papadimitriou, P. et al., 2015. The Santorini Volcanic Complex: A detailed multi-parameter seismological approach with emphasis on the 2011–2012 unrest period. J. Geodyn., 85, 32–57, doi: 10.1016/j.jog.2014.12.004. Papadimitriou, P. et al., 2018. The 12th June 2017 Mw=6.3 Lesvos earthquake from detailed seismological observations, Journal of Geodynamics, Volume 115, April 2018, Pages 23-42, ISSN 0264-3707, https://doi.org/10.1016/j.jog.2018.01.009. Papanastassiou D. 2011. Earthquake detection-location capability of the Hellenic Unified Seismological Network (HUSN) operating by the Institute of Geodynamics, National Observatory of Athens. Hellenic J Geosc 45: 209–216. Papazachos, B.C., Karakostas, V.G., Papazachos, C.B., Scordilis, E.M., 2000. The geometry of the Wadati-Benioff zone and the lithospheric kinematics in the Hellenic arc. Tectonophysics 319, 275–300. Sakellariou, D. et al., 2013. Strike slip tectonics and transtensional deformation in the Aegean region and the Hellenic arc: preliminary results. Bulletin of the Geological Society of Greece, XLVII, Proceedings of the 13th International Congress, Chania, Sept. 2013. Sigurdsson H.et al., 2006. Marine Investigations of Greece’s Santorini Volcanic Field, EOS, Vol 87 N. 34, 22 August 2006. Theodulidis N. et al., 2004. HEAD1.0 : A unified accelerogram database”, Seism. Research. Lett, 75, 41-50.

ABSTRACT. Greece is widely recognized as one of the most rapidly deforming regions in the world. Significantly large strain-rates are observed along the Hellenic Arc, owing to the active subduction of the eastern Mediterranean lithosphere beneath the Aegean, but also in the North Aegean Trough, caused by the westwards propagation of the North Anatolian Fault. In the framework of the HELPOS project, we collected a massive dataset of over 1900 focal mechanisms (Kapetanidis & Kassaras, 2019a) of Mw≥3.5 earthquakes that have occurred at focal depths of Z≤30 km to resolve the stress-field in a grid with node-spacing 0.25°, covering the entire region of Greece, using a damped least-squares inversion (Hardebeck & Michael, 2006). We then investigated the properties of the stress-field in terms of its principal stress axes orientations and stress-ratio to determine the main tectonic features across the Greek territory. The resulting stress-field is presented in Fig. 1a, interpolated in regions with insufficient data, such as the southern Aegean and the respective part of the volcanic arc, which are generally characterized by very low seismicity. NW Greece and Corfu Island are mainly affected by NE-SW contraction, favoring NW-SE reverse faulting and, in addition, strike-slip faulting, mainly in Epirus. Northern/central Greece and the Corinth Rift are primarily characterized by E-W normal faulting (Fig. 1b). Central Aegean, including Lesvos (e.g. Papadimitriou et al., 2018), Chios and Samos islands, is mainly governed by SW-NE dextral strike-slip faulting but also N-S extension (transtensional tectonics), with a very stable minimum principal stress axis (S3) in northern Aegean, also producing E-W normal faulting which becomes dominant near Dodecanese. The southern part of the Hellenic Arc around Crete is dominated by SW-NE sinistral strike-slip faulting with the presence of E-W reverse faulting, in the vicinity of the subduction zone. In W.Greece (e.g. Kassaras et al., 2016), SW-NE dextral strike-slip dominates along the Cephalonia-Lefkada Transform Fault Zone. The stress-field, and in particular the component of maximum horizontal compression, SHmax, was found in good agreement with the respective principal strain-rate axes determined by GPS/GNSS data, such as the Global Strain Rate Model (GSRM; Kreemer et al., 2003). Some differences are observed in areas of low strain-rate magnitude, as, for example in NW Greece, near Corfu, where the stress-field suggests compression more transverse to the Apulian collision front than the strain-rate field implies, and SW Aegean, where the strain-rate tensor is overwhelmed by the contraction along the Hellenic Arc, whereas the stress-field is related to strike-slip faulting near Crete and N-S normal faulting in southern Peloponnese and near Rhodes Island. To investigate the effects of the stress-field on the kinematics of known faults, the stress-tensor was applied on the fault-sources (FS) of the European Seismic Hazard Model 2013 (ESHM13; Woessner et al., 2015). In most regions, our results were found to be compatible with the ESHM13 FS, in terms of orientation and expected faulting type (Fig. 2), which was examined by imposing the direction of maximum shear on the fault plane as the direction of slip. Some differences were observed in regions of low strain-rate, such as the southern Aegean, where left-lateral strike-slip E-W faulting is expected, in contrast to the registered E-W normal FS. Discrepancies were also found in areas with complex tectonics, such as pull-apart basins in Western Greece, where the resolution of the regional stress-field is insufficient to explain local stress heterogeneities, or near the boundaries between regions with different tectonic regimes. Nevertheless, such areas were highlighted by anomalies in the stress-shape, Φ (Fig. 1c), which is strongly dependent on the variation of one principal stress axis while another remains relatively stable. A high Φ-value anomaly runs along the Andravida fault zone, which hosted the 8 June 2008 Mw=6.4 earthquake (e.g. Ganas et al., 2009) and further north along the normal and strike-slip zones of Lake Trichonis (e.g. Kassaras et al., 2014) and Amvrakikos gulfs. On the other hand, a low Φ-value, E-W oriented anomaly marks a significant rotation of the stress-field by 90° that occurs along the latitude=37°N, turning from E-W (in the north) to N-S (in the south) normal faulting in southern Peloponnese and Dodecanese Islands, as well as from dextral to sinistral SW-NE strike-slip faulting in northern and southern Aegean, respectively. The regional stress-tensor, which is available online at http://dx.doi.org/10.17632/sm8bj39nfy.1 (Kapetanidis & Kassaras, 2019b), can provide first-order knowledge that is useful for further studies involving focal mechanisms / fault kinematics, Coulomb stress transfer and seismic hazard assessment.

ABSTRACT. Ground deformation studies based on satellite geodetic measurements (GPS/GNSS) have been proved a unique tool to measure ground deformation in seismically active areas aiming to study the tectonic motions associated with earthquake procedures. The Central Ionian Islands is an area of high seismicity accompanied with large ground deformation due to the intense tectonic activity occurring in the area. In order to measure pre- co- and post-seismic activity in this area several local GPS networks have been established since 2001 covering the islands of Cephalonia, Ithaca and Zakynthos. Periodic GPS campaigns provided vital information of the motions that occurred prior and after strong earthquakes. The October 25, 2018 Zakynthos Earthquake (Mw=6.8) is a typical example of a strong event that caused intense deformation in the broader epicentral area, and the study of the ground deformation using GPS measurement revealed significant tectonic structures in the island.

ABSTRACT. The term Seismic Risk Assessment (SRA) is defined as the combination of a specified level of ground motion at a site (seismic hazard), the degree of damage expected to occur in its structures after an earthquake (seismic fragility) and the assets exposed (economic exposure). Given that the issue of the accurate prediction of earthquakes is strongly argued at present and physical limitations of Earthquake Early Warning Systems (EEWS) often impose restraints on their feasibility (Thelen et al., 2016), implementation of Rapid Seismic Risk Assessment (RSRA), highlighting urban regions prone to damage within the affected area, may crucially facilitate targeted emergency actions to be taken immediately after a disaster. To this aim, a GIS computer platform for semi-automatic deterministic RSRA is under development in the frame of HELPOS project, with the prospect to be linked to the near-realtime ShakeMap application of the Seismological Laboratory of NKUA towards acquiring an efficient, site-tailored, structural RSRA system. Herein we present its basic structure and an offline application on Cephalonia (Ionian Islands) that will be used as a baseline scenario of the platform’s validation at a later stage. Computational tasks within the system consist of Deterministic Seismic Hazard Assessment (DSHA) for a given earthquake taking into account site-effects and a combination of the derived Intensity Measures (IMs) with a predefined macroseismic EMS-98 vulnerability model (Grünthal, 1998). The output product includes spatial models (maps) of EMS-98 Damage Grades (DGs) and their probability to occur at the building block level. Key-point the platform is stressed to, is short delay in producing output, reduction of error-prone conversions and adaptations between modules/systems and a fully automated workflow. As mentioned above, platform output is fully localized, which requires site-specific parameterization regarding seismic sources, Ground Motion Prediction Equations (GMPEs), soil conditions and buildings taxonomy. Seismic source, i.e. its location, geometry, kinematics and its magnitude is the only variable in the workflow, input to a DSHA based on stochastic ground motion simulation implemented through the EXSIM module (Motazedian & Atkinson, 2005). Prior to automatic simulations, the appropriate GMPEs and soil conditions have been pre-determined by applying synthetic IMs generated by considering historical, instrumental and nearest Maximum Credible Earthquakes (MCEs), after validation with real damage observations. Path-effects are assumed after empirical GMPEs; site effects are approximated by experimental Horizontal to Vertical Spectral Ratios - HVSRs (Nakamura, 1989) and geotechnical borehole data. Hence, the platform’s EXSIM parameterization is considered to accurately resolve DSHA’s IMs, i.e. Peak Ground Acceleration (PGA), Velocity (PGV) or Displacement (PGD), Spectral Acceleration (Sa), Seismic Intensity (SI), defined as equivalent Modified Mercalli Intensity - MMI), however only by neglecting near-source effects and non-linear soil response. Vulnerability is input as indices, integrated into the platform in tabular form, linked to specific building classes and characteristics, and consists of a static component of the risk assessment application. This architecture allows flexibility for the input of different exposure files, renders the platform extendable to other areas and provides guidelines for structural data collection and exposure modelling in a standardized way. The structural vulnerability method selected to be implemented in the platform is the macroseismic semi-empirical method proposed by Giovinazzi & Lagomarsino (2004) that takes into account the EMS-98 classification (Grünthal, 1998) and additional typological-specific and seismic behavior modifiers, i.e. height, irregularities, building position, etc. The final outcome includes risk maps, in terms of collapse maps, distribution of number of buildings per EMS-98 DGs with maximum probability of occurrence. Consistently with international scientific practices for risk assessment studies at territorial level, the lowest tract at which the end product is provided, is seismic risk at building-block scale, because of the numerous uncertainties risk assessment is related to and also social privacy issues. The components that we put together have demonstrated good performance in the past when operated individually into several target sites in the Greek territory, i.e. Lefkada (Kassaras et al., 2015), Kalamata (Kassaras et al., 2018), Aigion (Giannaraki et al., 2018), Fira-Santorini (Kazantzidou-Firtinidou et al., 2018), yielding good agreement with real damage observations. Herein, we showcase seismic risk assessment of W. Cephalonia, pivotal for the platform’s validation, by exploiting damage observations due to the 26.1.2014 (Mw=6.1) and 3.2.2014 (Mw=5.9) earthquakes, ambient noise measurements during a post-seismic campaign and geotechnical data. Regarding the buildings’ inventory it was available by EPANTYK (2009) at building scale for the towns of Argostoli and Lixouri and aggregates per municipal district for the rest of the island. The derived IMs by the EXSIM scheme were found consistent with observed MMIs. Scenario DGs derived from the macroseismic approach were compared to the accumulated damage of the 2014 events, manifesting a satisfactory behavior of the constructions throughout the island, and a successful stress testing of the intended approach.

Acknowledgements This work is being developed within the project HELPOS - Hellenic Plate Observing System (MIS 5002697) which is implemented under the Action Reinforcement of the Research and Innovation Infrastructure, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020), co-financed by Greece and the EU.

References EPANTYK (2009) Development of GIS software for the representation of the structural wealth of the municipalities of the country and of its structural vulnerability in buildings block level. YP.ES.A, H.D, KEDKE, TEE, pp 39 (in Greek) Giannaraki, G., et al., 2018. Deterministic seismic risk assessment in the city of Aigion (W. Corinth Gulf, Greece) and juxtaposition with real damage due to the 1995 Mw6.4 earthquake, Bull. Earthq. Engin., doi: 10.1007/s10518-018-0464-z Giovinazzi, S, Lagomarsino, S., 2004. A macroseismic method for the vulnerability assessment of buildings, 3th WCEE, Vancouver, BC, Canada, August 1–6, paper No 896. Grünthal, G. (Ed.), 1998. European Macroseismic Scale 1998 (EMS-98). Cahiers du Centre Europeen de Geodynamique et de Seismologie 15, Centre Europeen de Geodynamique et de Seismologie, Luxembourg, 99 pp. Kassaras, I., et al., 2015. Seismic damage scenarios in Lefkas old town (W. Greece), Bull. Earthq. Engin., DOI:10.1007/s10518-015-9789-z. Kassaras, I., et al., 2018. Seismic risk and loss assessment for Kalamata (SW Peloponnese, Greece) from neighboring shallow sources, Bollettino di Geofisica Teorica e Applicata, 59, 1:1-26, doi: 10.4430/bgta0222. Kazantzidou-Firtinidou, D., et al., 2018. Empirical seismic vulnerability, deterministic risk and monetary loss assessment in Fira (Santorini, Greece), Nat. Hazards, doi: 10.1007/s11069-018-3350-8. Motazedian,D., Atkinson, G.M., 2005. Stochastic finite-fault modeling based on a dynamic corner frequency, BSSA, 95(3):995–1010 Nakamura, Y., 1989. A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. QR Railway Tech. Res. Inst., 30, 25-33. Thelen, W.A., et al., 2016. Feasibility study of EEW in Hawaii: U.S. Geological Survey, USGS O-F Report 2016–1172, 30 p.

ABSTRACT. We carry out a new probabilistic seismic hazard analysis (PSHA) for Lesvos Island, in the northern Aegean Sea. Being the most densely populated island and hosting the capital of the prefecture, its seismic potential has significant social-economic meaning. The new version of R-CRISIS module is used for the hazard estimation (Ordaz et al., 2017) which has high efficiency and flexibility in model selection. We incorporate into the calculations several different source models, as well as Ground Motion Prediction Equations (GMPEs) using a Logic Tree approach. This approach allows capturing the epistemic uncertainties in different input models by employing-considering alternative models in the hazard estimation (Bommer et al., 2005).

The earthquake source models (Fig. 1) include both line sources, representing seismogenic faults of the broader region, as well as area sources representing seismic zones. The hazard from these sources is computed based on the standard Cornell approach (Cornell, 1968). The assumption of the module is that within a source zone, seismicity is evenly distributed by unit area and thus all points might be potential earthquake focus. The sources corresponding to seismogenic faults are those included in the SHARE Database (Giardini et al., 2013), alongside those proposed by Papazachos et al. (2001). These are modeled both as area and line sources, with the latter resulting from the intersection of the fault with the ground surface.

The seismicity parameters, from a complete earthquake catalog spanning 106 years, were calculated within the area delimited by the green dashed line in Figure 1. The Lesvos Zone no (61), as proposed by Papaioannou and Papazachos, (2000) was also considered as an alternative zone model to the aforementioned. Using the Logic Tree approach, the six (6) in total different source models are combined into a single one, to account for the epistemic uncertainty in the hazard estimation.

The intensity measures used are Peak Ground Acceleration, (PGA), Peak Ground Velocity, (PGV), and Spectral Acceleration, (SA at T=0.2 sec). We calculated hazard curves for selected sites on the island: the capital Mytilene (Fig. 2), the village of Vrisa, in southeastern coast, which was partially ruined by the 12 June 2017 Mw 6.3 earthquake (Kiratzi, 2018 among others), Mythimna and Sigri, in the northwestern and southwestern part of the island, respectively. Hazard Maps are also presented in terms of all three intensity measures, for mean return period of 475 years (or 10% probability of exceedance in 50 years, assuming a Poisson process).

The spatial distribution of PGA in the hazard maps, using equal weights to all models, is between 0.27 g and 0.48 g, for PGV between 19 cm/s and 30 cm/s while the spectral values SA (0.2 sec) between 0.62 g and 1.0 g. According to the New Greek Seismic Code (EAK, 2003), Lesvos belongs to Zone II of 0.24 g.

Finally, the results regarding the two (2) area source models, which represent seismogenic faults, were disaggregated to depict the relative contribution of different earthquake sources and magnitudes to the results. The Edremit fault, right opposite of the northern shore of Lesvos, seems to contribute the most in the northern part of the island, which is something to be expected, being one of the most hazardous seismic sources in the broader region. The Agia Paraskevi right lateral fault (Chatzipetros et al., 2013), that cuts off the central part of Lesvos from N to S, has a significant contribution around the central part of the island, and especially in the village of Vrisa where small distance and big magnitude bins show elevated values.

The sources proposed by Giardini et al., (2013), except the two ones already mentioned, do not seem to contribute much to the final result. The most important factor leading to this are the activity rates, which, calculated from the average slip rate, are relatively low (<0.01 eq/yr). For a mean return period of 475 years, activity rates that low appeared insignificant in the calculations.

Acknowledgements We acknowledge support of this work by the project “HELPOS – Hellenic System for Lithosphere Monitoring” (MIS 5002697) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).

References Bommer, J., Scherbaum, F., Bungum, H., Cotton, F., Sabetta, F. and Abrahamson, N., 2005. On the Use of Logic Trees for Ground-Motion Prediction Equations in Seismic-Hazard Analysis. Bulletin of the Seismological Society of America, 95(2), pp.377-389. Chatzipetros, A., Kiratzi, A., Sboras, S., Zouros, N., Pavlides, S., 2013. Active faulting in the north-eastern Aegean Sea Islands. Tectonophysics, 597-598, pp.106-122 Cornell, C.A., 1968. Engineering seismic risk analysis. Bull. Seism. Soc. Am., 58, 1503-1606. EAK, 2003. Greek Seismic Code. Earthquake Planning & Protection Organization. Athens-Greece, ed., 72 pp and 7 appendixes (in Greek). Giardini D. et al., 2013, Seismic Hazard Harmonization in Europe (SHARE): Online Data Resource, doi: 10.12686/SED-00000001-SHARE, 2013. Kiratzi, A., 2018. The 12 June 2017 Mw 6.3 Lesvos Island (Aegean Sea) earthquake: Slip model and directivity estimated with finite-fault inversion. Tectonophysics, 724-725, pp.1-10. Ordaz, M., Salgado-Gálvez, M.A., 2017. R-CRISIS Validation and Verification Document. Technical Report. Mexico City, Mexico. Papaioannou, Ch. A. and Papazachos, B.C., 2000. Time-independent and time-dependent seismic hazard in Greece based on seismogenic sources, Bull. Seism. Soc. Am., 90, 22-33. Papazachos, B.C., Mountrakis, D.M., Papazachos, C.B., Tranos, M.D., Karakaisis, G.F. and Savvaidis, A.S., 2001. The faults that caused the known strong earthquakes in Greece and surrounding areas during 5th century B.C. up to present, Proc. 2nd Conf. Earthquake Eng. and Eng. Seism., 2-30 September 2001, Thessaloniki, Greece, 1, 17-26 (in Greek).

ABSTRACT. An effort to monitor seismicity and deformation across the Methana volcanic complex is under implementation. Our target is to monitor continuously any potential volcanic activity and deformation across the volcano using pilot applications of innovative seismic and geodetic methods. Aim of the project “GEORISK – Developing Infrastructure and Provision of Services through Actions of Excellence to Reduce the Impact of Geodynamic Hazards” is to assess the volcanic risk in the broader area that may affect maritime and air transport, in order to determine preventive measures. Even in the case of volcanic quiescence, seismological and geodetic data, derived from a permanent and temporary infrastructure, will define the level of volcanic status, hence the continuous (background) seismic-volcanic activity. We are deploying a network of permanent broadband seismic stations at the volcano and the neighboring islands. These stations will be incorporated in the Hellenic Unified Seismic Network (HUSN). A complementary deployment of temporary seismic stations will cover the entire volcanic complex aiming at the microseismicity monitoring and its association with tectonic or volcanic processes. In recent years, ambient noise interferometry (ANI) methods have been successfully used to detect temporal seismic velocity changes in volcanoes. Travel times between neighboring seismic stations are constantly obtained from their cross-correlation function (CCF) of ambient seismic noise. Thus, relative velocity changes in the Earth crust are likely to be caused by the change of stress and/or volume within the volcano and are accounted as precursors to volcanic events. The ground motions in the Methana volcanic complex will be also investigated geodetically by means of a non-permanent GNSS network along with one continuously recording GNSS station. An extensive experience on similar studies and network deployments in Santorini, Milos and Nisyros volcanic complexes assists on the optimal design of the seismic and geodetic network able to monitor, in a cost effective way, temporal changes across Methana volcano.

ABSTRACT. The study area is situated in East Attica approximately 15km east of Athens (Greece), consisting of a small catchment (area 115km2) drained by Megalo Rema torrent.In this study delineated floodplain areas along the final 4km of the main stream M.Rema, by using the coupling of hydraulic modeling Hec-RAS (Hydrological Engineering Center’s River Analysis System) and G.I.S (Geographical Information System).The flood plain delineation exercises repeated for three discharges values: (A) discharge value of the storm event on 22/02/2013, (B) discharge value for return period 25 years, (C) discharge value for return period 50 years. The results of the hydraulic simulation (HEC-RAS), fully correspond to the recorded construction’s damages of the storm event on 22/02/2013.

ABSTRACT. Boundary And Estimation Of the Flood Development Velocity Using Unmanned Aerial Vehicle (UAV)-Derived Imagery And Ground Observations: The Case Of The 2017 Mandra Flash Flood In Greece Spyrou1, N-I., Stanota1, E-S., Diakakis1, M., Andreadakis1, E., Deligiannakis2, G., Lekkas1, E. (1) Department of Geology and Geoenvironment, Zografou Athens, Greece, nspyrou@geol.uoa.gr. (2) Agricultural University of Athens, Athens, Greece

Background

The use of Unmanned Aircraft Vehicle (UAV) can make a decisive contribution to response to hydro-meteorological natural disasters increasingly affecting the Mediterranean region. UAVs can be used to identify, study and recover environmental impacts, as well as to improve data monitoring and recording using on board innovative sensors. The UAV in disaster management provides direct and detailed impact recording even in inaccessible areas. It also provides images and maps of enhanced resolution, especially on flash flood phenomena, in the case of which the spatial and temporal scales of occurrence do not favor traditional monitoring processes. The flash flood of west Attica on November 15 2017 has caused enormous damage on human and natural environment and a tragic loss of 24 people. The complexity of impacts typology and its distribution in space, highlighted the need to study the event, in terms of evolution and mapping of its extent and physical characteristics. The analysis with the use of UAV produced detailed flood extent and provided a comprehensive description of the characteristics of floodwaters within the flooded area.

Objectives

The research team studied the area during the flood and the day after, using a combination of ground and aerial observations with the aid of an unmanned aerial vehicle (UAV). The aim of this study is to identify different types of flood extent indicators, including mudlines, debris lines and others, based on collected imagery, which were recorded and lead to flood boundary delineation across the inundated area. In this work, the rate of flood development velocity is also estimated using the data which were collected through aerial and ground observations, including snapshots with specific timeframe. This study shows how aerial observations can improve the accuracy of defining the extent of floods and the speed of their deployment that in turn is very useful for risk mitigation efforts. UAV flights took place a few hours after the flood of November 15, 2017 and on November 16, 2017. The flood affected the western part of Attica in the city of Mandra and Nea Peramos and reached 300 mm in 13 hours causing 24 deaths and extensive damage to property and infrastructure.

Methods

• Research was carried out with ground and aerial observations on the flight of a UAV. Photos and videos were captured using the UAV in several flights, as well as ground observations and images. • The collected data were analysed and processed and the collected images were georeferenced. • The types of high - water marks were studied, categorized. The depth and the extent of the flood were assessed. • The estimation of the water flow rate was based on the hydraulic head and the flow of objects on the water surface was based on videos and photos material which taken during the flood. • In order to evaluate the characteristics of the flow and its speed, video snapshots, images of terrestrial and aerial observations that were selected, were analyzed. This data involved flowing obstacles such as trees, buildings and other facilities. • Regarding the estimation of the water velocity, the variation of the water level on the same position at different times was also studied.

Results

According to the analysis of the collected data from the combined use of the aerial and ground observations [Fig 1], we achieved the accurate estimation of the flood extent and the definition of its characteristics. These characteristics were related with the boundaries, the depth and the speed of the flood. In this study the types of the flood boundaries were analyzed and categorized. The speed of the water during the flood reached 10 m / s, the depth reached 4.2 m and the flood area was 4.03 km2.

Figure 1. Display of the flood boundaries in the industrial area of Mandra with the use of UAV.

Conclusions

The UAV allowed the collection of aerial photographs in an extended area during flood flows despite that a large portion of it was inaccessible due to road closures and safety issues. This way a large part of the useful data was captured in short time during and after the flood. Especially in the case of flash floods which are characterized by a rapid rise and withdrawal of floodwaters, it is virtually impossible for a field survey team to reach different parts of the inundated area and make ground observations during the actual phenomenon. As flood effects and flood marks of all kinds (e.g. high water marks, flood deposits) were removed during cleanup efforts in the days following the disaster, there was limited time to cover the whole affected area with detailed ground observations. In this case, the integration of aerial observations in post-flood analysis provided guidance to intensify ground observations at key locations where it was needed, in time before crucial evidence disappeared. This work demonstrated that the combination of aerial and ground observations allowed an accurate reconstruction of the 2017 flood, contributing to flood extent and water depth determination, peak discharge estimation and detailed mapping of impacts. The approach is considered to have several advantages connected with the collection of data during flash flood investigations and is capable of providing a holistic overview of multiple aspects of a flood that can be valuable to both science and civil protection. Aerial observations can act as an extra point of observation that accompanies the traditional ground-based field survey and fits well in the opportunistic nature of this type of studies.

References

Diakakis, Μ, Andreadakis, Nikolopoulos, E.I., Spyrou, N.I., Gogou, M.E., Deligiannakis, G., Katsetsiadou, N.K., Antoniadia, Z., Melaki, M., Georgakopoulos, A., Tsaprouni, K., Kalogiros, J., Lekkas, E. (2018). An integrated approach of ground and aerial observations in flash flood disaster investigations. The case of the 2017 Mandra flash flood in Greece. International Journal of Disaster Risk Reduction, Elsevier, 33, pp 290-309 Suzette, M. K. (2016). Identifying and Preserving High-Water Mark Data. Chapter 24 ofSection A, Surface-Water Techniques Book 3, Applications of Hydraulics, USGS Gaume, E., Borga, M., 2008. Post-flood field investigation in upland catchment after major flash flood: proposal of a methodology and illustrations, Journal of flood Risk Management, 1 (4), 175-189

ABSTRACT. The climate changes are related necessarily to the increase of the earth’s temperature resulting to a sea level increase. Such continuous events, with smaller minor and greater intensity, were taking place during the alternation of warm and cool periods in the Earth during the Late Quaternary and the Holocene periods. However in the last decades, has taken place a particularly significant awareness by the scientific community, and consequently to the greater public, that a climatic change will take place very soon, or it is on going. As a consequence it is important to carry out soon actions. However such a case has not been recorded yet and the necessary actions are not required for the time been.

ABSTRACT. Introduction Landslides induced by the 2017 Lesvos Earthquake (North Aegean Sea, Greece) are presented along with their controlling factors and the engineering measures for landslide disaster mitigation. All presented data were derived from the research program applied in the earthquake-affected areas of southeastern Lesvos Island and conducted by the authors. The 2017 June 12 Mw 6.3 Lesvos earthquake On June 12, 2017 (12:28 GMT) an Mw 6.3 earthquake struck Lesvos Island (Northeastern Aegean, Greece) with focal depth of about 13 km and epicenter located offshore Plomari town (southeastern Lesvos). The main shock was generated by the rupture of the northern margin of the offshore Lesvos basin located between Lesvos Island in the north, Chios Island in the south and İzmir bay in the east (Papadimitriou et al. 2018). As regards the geodynamic setting, the North Aegean constitutes an extensional zone south of the North Anatolian dextral strike-slip fault zone and north of the Hellenic Trench (e.g. Le Pichon and Angelier, 1981). The small scale uplift of the Aegean area enables Anatolia to move with increasing velocity towards WSW resulting in the formation of the İzmir bay and the offshore Lesvos basin, which is bounded by E-W striking normal faults (Mascle and Martin 1990). Earthquake environmental effects Among the impact on public health (1 casualty and 15 injured people) and on the built environment (structural and non-structural damage in buildings), the earthquake also generated secondary environmental effects comprising mainly slope movements, ground cracks and a small-scale tsunami (Lekkas et al., 2017, Mavroulis et al., 2018). Slope movements were observed in several sites of the affected area resulting in partial damage to the road network including cracks and craters in the asphalt pavement and deformation of road protection barriers as boulders bounced across the roads, damage to adjacent building structures and related facilities and temporary or permanent traffic disruption (Mavroulis et al., 2018). Factors controlling the earthquake-induced landslides The observed slope movements are mainly attributed to pre-existing instability conditions formed in geotechnically unstable areas and landslide zones, presence of active faults forming intense relief with high and abrupt slopes and scarps, as well as suitable geometry of beds and discontinuities dipping towards the free face of slopes. Moreover, the eastern part of Lesvos Island is characterized by an arid to semi-humid climate, which is accompanied by relatively large surplus of water during the winter period (Karras, 1973). On the other hand, the western part of Lesvos Island is characterized by semi-arid climate with a small surplus of water during the winter period and high potential of evapotranspiration. The prevailing winds are northern and the southern winds follow. The distinction of the island into different climatic types reveals the difference in the occurrence of landslide phenomena between the two parts, with the eastern part having more landslide phenomena that the western one. Local geological and morphological setting and types of the observed earthquake-induced slope movements The research team conducted a detailed mapping of the sites affected by the earthquake-induced slope movements by combining not only the classical geological and geotechnical mapping but also modern and innovative mapping techniques including Unmanned Aerial Vehicles (UAV). The observed slope movements were classified into: • Wedge detachments, planar slides, toppling failures or movements due to combination of these slope movements attributed to the synergy of bedding, schistosity and fractures. • Rotational landslides and failures of the soil, of the weathering mantle and of the surficial parts of the loose rockmass of the schists and pyroclastic rocks. Slope movements were observed in the Agios Isidoros, Akrassi and Mesotopos areas and along Plomari – Melinta – Palaiochori road network. Agios Isidoros and Plomari – Melinta – Palaiochori areas are composed of alpine formations including blueschists and marbles of Carboniferous age. These series also comprise carbonaceous metaconglomerates and large masses of greenschists. The affected areas are characterized by intense morphological slopes and morphological discontinuities, which locally are equal to or larger than 100 %, while the majority of the affected areas are characterized by slopes varying mainly from 51 to 100% and secondarily from 11 to 50 %. During the 2017 earthquake, rockfalls, planar slides and wedge failures occurred in Agios Isidoros and Plomari – Melinta – Palaiochori areas. Akrassi area is located east of the homonymous village and along the road network leading from Akrassi to Plomari. This area comprises Neogene ignimbrites lain unconformably over marbles, schists and ophiolites. Ignimbrites are composed of massive sheets with strong cohesion with flat surface overlying eroded surfaces of alpine formations. This area is characterized by intense morphology and slopes varying mainly from 51 to 100 % and secondarily from 11 to 50 %. During the 2017 earthquake, the generated slope movements in Akrassi included rockfalls and landslides. Mesotopos area is located east of the main provincial road leading from Agra to Mesotopos. Ii is comprised by lava layers and pyroclastic rocks. During the 2017 earthquake, rockfalls were generated and affected the part of the aforementioned road. Proposed engineering measures for the landslide disaster mitigation The proposed engineering measures for the landslide disaster mitigation include the following: • Removal of hanging, unstable and isolated rock blocks or of the loose rockmass • Cleaning of the landslide materials accumulated behind retaining walls in order to create space for future slope movements and accumulation of mobilized material. • Construction of concrete retaining walls along the base of natural or artificial slopes • Simple and quick construction of gabion walls with flexibility to withstand foundation movement and with space behind them in order to receive and safely sustain loads of mobilized material • Support and reinforcement anchors along with fastening of wire meshes over slopes with highly fractured, brecciated and loose rockmass • Construction of concrete retaining walls along with landslides and rockfalls protection fenches on their top • Excavation of horizontal benches into slope face for protection from rockfalls and the reduction of tensional forces in the surface rock and of surface erosion rates • Construction of dynamic rockfall barriers • Combinations of systems often provide the most effective solutions

ABSTRACT. Seismic risk is determined by the combination of the probability of occurrence of a specified level of ground motion in a specified period of time (seismic hazard), the degree of damage expected to occur in structures after an earthquake (seismic fragility) and the assets exposed in a given area (economic exposure). Seismic risk assessment can provide critical information to stakeholders for the development of efficient risk reduction measures. However, in many cases observed ground motions are found to be underestimated by seismic hazard maps, due to lacking experience of strong earthquakes near urban areas and hence a questionable awareness of building stock endurance. In this work we present a physical risk model for the old part of Heraklion city (Crete). Crete is located in one of the most seismically active domains of eastern Mediterranean, marking the tip of the southern Hellenic subduction zone. Crete is considered also to be of high importance for the Greek tourism, estimated that contributes at around 47% of the GDP. Heraklion, is the third most populated city of Greece. It is situated at the north-central coastal area of Crete, thus it is prone to strong earthquakes as manifested by the seismic history of the area (Papadopoulos, 2011) and the presence of several active faults in its vicinity. During the history of the city, several shallow and intermediate depth damaging earthquakes have occurred. Although instrumental and historical evidence does not indicate that Heraklion was damaged by earthquakes triggered by nearby shallow faults producing adverse effects to the city, a future incident cannot be excluded (Papazachos, 1995). According to the effective Greek seismic code (ΕΑΚ-2000), Heraklion belongs to seismic hazard zone II for which predicted peak ground acceleration is PGA=0.24g. However, the above consists only an abstract approach, neglecting local conditions that may largely alter the effects of natural phenomena at a site. Therefore, a modern plan taking into account local conditions is required to facilitate effective interventions and mitigation policies. To this aim, we develop a comprehensive seismic assessment by combining the exposure and vulnerability model of the old part of Heraklion city with the SHARE seismic zones (Giardini et al., 2014) and site response deduced from geotechnical data and microtremors measurements in order to acquire both probabilistic and deterministic earthquake loss assessments. The GEM OpenQuake-engine (OQ - www.globalquakemodel.org/openquake) was used to identify the regions with the highest risk within the target site, the most vulnerable assets, and the expected economic losses for a number of return periods and also for the most hazardous seismic sources in the vicinity of the city. The public-private Global Earthquake Model (GEM) foundation is an international pioneer that hosts an open initiative to develop state-of-the-art, widely accepted datasets, models and open-source tools/software for seismic risk assessment. The herein work is organized as following. Path-effects were assumed after empirical GMPEs; site effects were approximated by experimental Horizontal to Vertical Spectral Ratios - HVSRs (Nakamura, 1989) obtained during an in-situ survey of microtremors measurements (ASPIDA, 2015) and geotechnical data (Auto-Seismo-Geotech, 1998). The census exposure model was available by EPANTYK (2009) and the corresponding fragility/vulnerability functions from the OpenQuake-platform (www.globalquakemodel.org/oq-platform). To assess the impact of soil response, the loss model was calculated with and without taking into account site amplification functions. Results were mapped using GIS tools. Fig. 1 presents the resolved Probabilistic Seismic Hazard Assessment (PSHA) for the old city of Heraklion using OQ, SHARE Area Sources (AS), attenuation laws from the literature and site amplification. Site amplification was approximated by VS30, derived from ambient noise HVSR (ASPIDA, 2015) and geotechnical borehole NSPT measurements (Auto-Seismo-Geotech, 1998). VS30 was obtained by inversion of the HVSR curves using ModelHVSR (Herak, 2008) and empirical relations (Tsiambaos & Sabatakakis, 2011) for the two data types, respectively. Probabilistic PGA values were found to range from about 370 to 470 cm/s2, somewhat higher than values predicted in the global maps of the SHARE project (http://www.efehr.org/en/hazard-data-access/hazard-maps) calculated for rock conditions (VS30=800 m/s), being of the order of 350 cm/s2. Moreover, these are significantly larger than the value of 0.24 g predicted for the area by the national seismic code (EAK-2000). Fig. 2 illustrates the outcome of a scenario-damage calculation regarding a Mw6.5 earthquake on a N-S trending, east-dipping normal fault source located west of Heraklion (SHARE-GRCS740 fault source). The scenario, appears relatively amenable for the building stock implying a small percent (6%) of the buildings prone to undergo extensive damage or collapse, corresponding to 220 buildings out of the ~4000 ones in the target site available from the census data. In conclusion, the ongoing analysis manifests a robust methodology that yields consistent seismic risk assessments, which could be of use of stakeholders towards decisions on mitigation measures.

Acknowledgements We would like to acknowledge G. Giannaraki, S. Mourloukos, P. Stoumpos, for their valuable help that greatly contributed in the current research. We thank A. Ganas and D. Kazantzidou-Firtinidou for discussions. I.K. thanks ASPIS-KRIPIS (MIS-448326) and HELPOS - Hellenic Plate Observing System” (MIS 5002697) research projects.

References ASPIDA, 2015: Infrastructure Upgrade for Seismic Protection of the Country and Strengthen Service Excellence through Action, project MIS-448326, implemented under the Action, Development Proposals for Research Bodies-ASPIS-KRIPIS (in Greek). Auto-Seismo-Geotech, 1998. Automated geotechnical program for the prevention and mitigation of seismic risk of seismic prone cities in the framework of analytical microzonation studies titled: Geological Survey of the Heraklion Crete area, H3A, Ministry of Development-GSRT, EPET II (in Greek). Boore, D.M., 2003. Simulation of ground motion using the stochastic method. Pure Appl Geophys 160, 635–676. EAK-2000 (2003) Greek National Building Code, Earthquake Protection and Planning Organization of Greece. EPPO Publ., Athens. EPANTYK (2009) Development of GIS software for the representation of the structural wealth of the municipalities of the country and of its structural vulnerability in buildings block level. YP.ES.A, H.D, KEDKE, TEE, pp 39 (in Greek) Giardini, D., Woessner J., Danciu L., 2014. Mapping Europe’s Seismic Hazard, EOS, 95(29), 261-262. Herak, M., 2008. ModelHVSR–A Matlab tool to model HVSR of ambient noise. Computer & Geosciences, 34, 1514-1526. Milutinovic, Z., Trendafiloski, G., 2003. An advanced approach to earthquake risk scenarios with applications to different European towns. ReportWP4: vulnerability of current buildings, Risk-UE. EC, Brussels, DOI: 10.1007/978-1-4020-3608-8_23. Nakamura, Y., 1989. A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. QR RTRI, 30, 25-33. Papadopoulos, G.-A., 2011, A seismic history of Crete, First Ed., Ocelotos Public., Athens. Papazachos, V., 1995. Faults of the big earthquakes (Ms>8.0) in the Hellenic arc, Proc. XV Congress of the Carpatho-Balcan, Geological Association, Athens, Greece. Tsiambaos, G., Sabatakakis, N., 2011. Empirical Estimation of Shear Wave Velocity from In Situ Tests on Soil Formations in Greece, Bull. Engineering Geology and the Environment, 70, 291-297.

ABSTRACT. Introduction According to the new Solvency II EU Directive, each insurance company specifies the required capital, in order to ensure that it will be able to meet its obligations over the following year, with a probability of at least 99.5%. In order to accurately calculate the Solvency Capital Requirements (SCR) for earthquake perils, insurance companies can utilize either the Standard Formula (SF) as defined in technical papers approved by the European Insurance and Occupational Pensions Authority (EIOPA), or an internal Earthquake CAT model. The SF is based on past earthquake events and their corresponding insured losses, thus inheriting problems related to the incompleteness and the inhomogeneity of the historical records and lower spatial resolution of hazard (e.g. Grützner et al., 2013; Papanikolaou et al., 2015). Furthermore, it incorporates rough assumptions so that it can fit every insurance company in EU, only by adjusting the country factor, the risk zone weights and the correlation matrix for all Catastrophe Risk Evaluation and Standardizing Target Accumulations (CRESTA) zones in each country (European Commission, 2010). Methodology A newly developed Synthetic Stochastic Earthquake Catastrophe model is applied in the Region of Attica, Greece. It consists of three basic modules: Hazard, Vulnerability (including the Exposure) and Loss modules. We use a fault specific seismic hazard assessment approach for the Hazard Module, in order to address problems related to the historical records incompleteness, aiming on the reconstruction of a more complete earthquake catalogue over a larger period of time (~15,000 years, i.e. during the Holocene), obtain higher spatial resolution and calculate more realistic source locality distances. The method of seismic hazard mapping from geological fault throw-rate data was firstly introduced by Papanikolaou (2003) and Roberts et al., 2004. It is based on an active faults database with 24 faults that are long enough to produce surface ruptures and can sustain damage in the Attica mainland in case of earthquake rupture, affecting the Attica Region (Deligiannakis et al., 2018) Epicenters induced by fault modeling, along with the catalogue events are stochastically simulated in order to project the future earthquakes. Attenuation relationships and amplification/attenuation factors based on the surface geologic conditions are then applied to each epicenter, in order to simulate future earthquake scenarios (Figure 2, Left) and assess spatial distribution of the MM Intensity. The structural damage in buildings and the corresponding loss is computed using the Vulnerability Module, which is based on existing values (e.g. Sauter & Shah, 1978; Degg, 1992) (Figure 2, Right). For the calculation of the SCR (Loss Module), a large dataset of simulated earthquake events is composed. The corresponding losses are either ranked in descending order, so that the appropriate arranged value can be selected, or a theoretical distribution is fitted over the whole sample of simulated losses. Results - Conclusion Overall, for the whole Attica Region buildings inventory, the SCR calculated using the SF is overestimated by 15% compared to the hereby presented EQ CAT Risk Model. However, in 7 out of 10 CRESTA Zones in Attica, the SCR calculated by the SF was 3 – 57% higher, while in the remaining 3 cases it was 19 – 49% lower. These variations result from the differences on the spatial analysis, the local site conditions and the variations in seismic intensity recurrences throughout the same CRESTA Zone. For example, in CRESTA Zone “14” (Figure 3, left) the postal codes with low or zero intensity VIII recurrence are the ones with the largest insured values and thus the Earthquake CAT Model estimates a 57% lower SCR than the SF. Similarly, our model calculates the smallest SCR for the CRESTA Zone “16”, compared to the rest of the CRESTA Zones of Attica. Nevertheless, there are still some Postal Codes within that Zone that have experienced intensity VIII and even IX in low recurrence (Figure 3, right). However, this CRESTA Zone is attributed to an extremely low CRESTA relativity factor (0.6), which seems to result in an SCR 55% lower than our model.

ABSTRACT. How and why catastrophic explosive volcano eruptions occur? These explosions are accompanied by the ejection of vast amounts of gases and pyroclastic material, glowing clouds, surges, etc., and lead to great human and material losses, as well as exerting a significant, in some cases, long-term impact on the Earth’s atmosphere and climate. It is assumed that this phenomenon is considered with degassing of magmas in relatively shallow transitional magma chambers beneath volcanoes, i.e. decreasing of gas solubility in the melt due to decrease of temperature and pressure. If the melt is saturated in volatiles, it can spontaneously expel the gas, i.e., begins to resurgent (retrograde) boiling. The scale of this process evidently depends on initial volatiles saturation in the melt and its energy state related to the formation and growth of gas bubbles in the melt because it is energy-consuming process (Sharkov, 2004). However, it is not clear yet why does magma degassing occasionally lead to catastrophic explosions which can last 2–4 months. Most geologists suggest that catastrophic explosions are related to an abrupt increase of magma volume in shallow chambers owing to degassing. The relevant models suggest the following causes of explosions: groundwater penetration into magma chamber, collapse of volcanic cone, emplacement of gas-saturated basaltic magma into dacite magma chamber, penetration of magma chamber by fractures–conduits, etc. Unfortunately, none of these models explains the vast scale and long duration of the process, as well as specific mechanism of the large-scale bubble formation required for such explosions. The above phenomena actually can affect the eruption style in some cases; however, they cannot cause the catastrophic scale. All these hypotheses consider the explosion itself, but do not explain the high gas content in melts and the mechanism of practically simultaneous separation of gas bubbles in a significant volume. We believe that the process is mainly controlled by kinetic factors, because the formation of a new interface requires significant energy consumption. This is typical of any phase transition, including resurgent boiling of melt, which is considered here. Therefore, the formation of numerous nuclei of a new phase (crystals, melt, or gas) in the previously homogeneous medium can occur only after an energy barrier is overcome. Then, the process proceeds without problems, since it operates within the stability field of the new phase. The formation of a few nuclei owing to fluctuations cannot be developed to a large-scale process, because the increase of an existing bubble-melt interface is energetically more favorable than the formation of a new one. Therefore, for example, local decompression because of a fracture in the chamber’s roof, can cause the growth of group of bubbles or lead to local magma foaming during filling of this fracture. According to experimental data (Fluids…,1991), the solubility of water and CO2 in mafic and felsic melts increases with pressure up to 3 GPa without extremes (Fig. 1). Unlike water, CO2 solubility significantly depends on the melt composition, being the lowest in the felsic and intermediate magmas. In other words, water should be the dominant component of the gas phase in rhyolites and dacites of calc-alkaline series, typical for convergent tectonic settings, whose eruptions are typically catastrophic. The experimental data also indicate that water solubility in the melts remains nearly constant during pressure decrease to about 0.1 GPa and then abruptly decreases. Unlike water, the CO2 solubility gradually decreases with decreasing pressure, and only weakly depends on the initial CO2/(CO2 + H2O) ratio. From this follows that subduction-related water-bearing andesite–dacite magmas can become oversaturated in H2O owing to abrupt pressure decrease under shallow conditions in peripheral chambers of volcanoes at depths of 3–4 km. In this case, melt in the magma chamber presents a “blasting” mixture, which is ready to explode at any moment owing to rapid degassing. Seismic observations show that the upper magma chambers beneath the most andesite–dacite volcanoes are located at these depths (2–8 km) (Macdonald, 1972). Hence, such situations frequently occur in nature. However, as follows from experimental data, even the water-oversaturated melt cannot boil spontaneously without any additional impact or can boil only by scoria formation, as takes place during the eruption of intraplate basalts. Large-volume separation of gas bubbles requires a mechanical shock-type impact: the melt must be abruptly compressed and subsequently decompressed (Stolper, 1982). In this case, gas bubbles begin to form over the entire magma volume in chamber. We believe that this mechanism can be applied to catastrophic volcanic eruptions. The volatile-saturated melt in a shallow chamber can explode owing to a strong earthquake, when pressure abruptly increases in the compression front and abruptly decreases in the subsequent expansion front. So, presence of volatile-rich magma as well as some energy pulse behaving as a “trigger,” which causes the rapid and extensive formation of gas phase nuclei, are necessary for a catastrophic explosion. This mechanism is especially efficient during a series of earthquakes, which usually precede catastrophic explosions; resurgent boiling begins at the moment when the energy barrier is overcome. During a further (stronger) impact, many homogeneously scattered gas bubbles are formed in magma. It is highly improbable that the entire chamber volume is spanned by this process, since pressure in the chamber can increase downward to 0.15–0.3 GPa (Macdonald, 1972), thus blocking further formation of bubbles. However, this pressure is sufficient for explosion and ejection of the material. At the moment of explosion, the magma chamber is impacted by the explosion-related shock wave, which is followed by the expansion front, thus again allowing large-volume degassing and a new explosion, and so on. Such a mechanism determines the layer-shape resurgent boiling zone related to frontal propagation of shock waves. However, in any case, this zone, owing to explosions, will migrate downward, primarily develop at the shallower sections of the magma chamber, and gradually remove the melt from it. If the chamber has a significant vertical extent, it can be emptied to depths of about 5–6 km, since the melt at larger depths may be undersaturated in H2O and retrograde boiling will stop. Calderas can form owing to the chamber emptying, and the volcano will become inactive until the formation of a new chamber by water-saturated magma replenishment, after which the process can repeat.

Fig. 1. Scheme illustrating the structure of the magmatic systems related to subduction zones at the active margins of continents and oceans. (a) Structure of the system: (1) continental lithosphere, (2) oceanic lithosphere, (3) subducted plate, (4) magma chamber. (b) Variations of H2O and CO2 solubility in silicate melt versus pressure (simplified after (Liquid…, 1991).

Thus, the most important prerequisites for the catastrophic explosive volcanic eruption are as follows: (1) presence of water-saturated felsic–intermediate melts in shallow chambers at depths of 3–5 km and (2) seismic activity of the region. The presence of other volatiles (CO2, SO3, etc.) does not play significant role. This could explain prior association of catastrophic explosions with subduction-related magmas and relative scarcity and small scale of explosive processes during intraplate magmatism, which is dominated by eruptions of basalts with CO2 as the main volatile. However, it does not exclude strong explosions in the shallow trachyte and trachyrhyolite chambers, which occasionally occur in plume-related large igneous provinces.

References Sharkov, E.V., 2004. Role of the energy of interface formation in the melting and retrograde boiling. Geochemistry Intern., 42(10), 950-961. Fluids and Redox Reactions in Magmatic Systems, 1991. Ed. by A. A. Kadik (Nauka, Moscow,) (in Russian) Macdonald, G. A., Volcanoes (Prentice Hall, Englewood Cliffs, 1972; Mir, Moscow, 1975). Stolper, E. 1982. The Speciation of Water in Silicate Melts. Geochim. Cosmochim. Acta 46, 2609–2620.

ABSTRACT. Assessment of risks to human health and the environment, related to exposure of metals in agricultural soil (arable land) and grazing land soil (grassland), is one of the requirements under the European Commission’s REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulation. The regulation required the development of pan-European harmonised soil geochemical data sets for agricultural and grazing land and, thus, the emergence of the GEMAS project (GEocheMistry of Agricultural and grazing land Soil) of the EuroGeoSurveys Geochemistry Expert Group. The project addressed the data gap and data quality requirements imposed by REACH, i.e., monitoring data were collected for metals in agricultural soil (arable land 0-20 cm) and grazing land soil (grassland 0-10 cm) from 33 European countries, using a harmonised sampling protocol, and all samples were prepared and analysed at the same laboratory for the same suite of determinands. Geochemical maps display a distinct element concentration break between northern and southern Europe delineating the limit of the last glaciation. This concentration break can be recognised for many elements, both nutrients (e.g., P, Mg, Zn, Cu) and toxic ones (e.g., Pb, As, Hg, Cd), and it is strongly controlled by underlying geology and climatic conditions. The signature from fertilisers and other land-use play subordinate role at the continental scale.

ABSTRACT. Introduction In Europe, three continental-scale geochemical projects were carried out at different times to fulfil a variety of purposes and uses. The first, the FOREGS Geochemical Atlas of Europe was carried out from 1997 to 2006, with the publication of a two-volume atlas (Salminen et al., 2005; De Vos, Tarvainen et al., 2006), as a contribution to the Global Geochemical Baselines project of the International Union of Geological Sciences for the establishment of the European Global Geochemical Reference Network (Darnley et al., 1995). It covered 26 countries and an area of 4.25 million km2. The second, European Groundwater Geochemistry (EGG) project was carried out from 2007 to 2010, with the publication of a one-volume atlas (Reimann and Birke, 2010); this rather unique cost-effective project used as sampling medium bottled mineral water as a proxy to the geochemistry of groundwater. The third, GEMAS (GEochemical Mapping of Agricultural and grazing land Soil), was carried out from 2008 to 2014, with the publication of a two-volume atlas (Reimann et al., 2014a, b); it covered 33 European countries and an area of 5.6 million km2. Materials and methods In the FOREGS Geochemical Atlas of Europe project, samples of stream sediment (n=799), stream water (n=807) and residual soil (top 0-25 cm; n=845; bottom >75 cm; n=788) were collected from drainage basins of <100 km2 in area, and floodplain sediment (top 0-25 cm; n=743) from drainage basins of 1000-6000 km2 in area; the average density of each sampling medium was approximately 1 sample/4700 km2. Methods of sample collection, sample preparation, laboratory analysis, quality control procedures and data processing are described in Salminen, Tarvainen et al. (1998) and Salminen et al. (2005). The EGG project bottled mineral water samples were purchased from supermarkets (n=884), and the analytical, quality control and data processing procedures are described in Reimann and Birke (2010). The field methods used in the GEMAS project for the sampling of agricultural soil (0-20 cm; n=2108), and grazing land soil (0-10 cm; n=2023), laboratory methods and quality control procedures are described in detail in EGS GEG (2008) and Reimann et al. (2014a).

Results and discussion As Li is an important critical element for future sustainable technologies according to UNEP (2009), but is not yet in the list of critical materials of the European Commission (2017), it is used as an example. The geochemical maps of Li in agricultural soil from the GEMAS project (Figs. 1a), and Li in floodplain sediment from the FOREGS project (Fig. 1b) display overall similar patterns. The most striking feature on all geochemical maps is the discrete element concentration break at the maximum extent of the last glaciation, a feature that is even shown on the map of Li in bottled mineral water from the EGG project (Fig. 1c). The agricultural soil, floodplain sediment and bottled mineral water maps, display overall lower Li values to the north of this break compared to those in the south. Hence, there are at least two distinctly different Li background ranges at the continental-scale. Comparing the geochemical maps with the Li mineralisation and mineral deposits map from the ProMine Mineral Database (Fig. 1d), the FOREGS, GEMAS and EGG project continental-scale geochemical maps exhibit overall anomalous or elevated concentrations in the vicinity of most of these occurrences. From the mineral exploration point of view, the anomalous samples shown on the bottled mineral water Li map (Fig. 1c) should be of even greater interest, as they depict the geochemistry at depth. It is stressed that in all projects the objective was to map the geochemical background element variation. However, all three geochemical maps (Fig. 1) show many areas that warrant more detailed surveys for the delineation of areas of mineral potential for Li. In conclusion, the results of the three continental-scale geochemical surveys demonstrate the variable geochemical background across Europe. It needs to be defined for each determinand in each sample medium. For environmental impact studies a site-specific background level will need to be established. Further, all data sets can be used for area selection for more detailed mineral exploration.

Acknowledgements The FOREGS, EGG and GEMAS projects are cooperative team efforts of the Geochemistry Expert Group of EuroGeoSurveys (http://www.eurogeosurveys.org/), and all teams are thanked for their input.

References Darnley, A.G. et al., 1995. A Global Geochemical Database for Environmental and Resource Management. Recommendations for International Geochemical Mapping – Final Report of IGCP Project 259. Earth Science Report 19. UNESCO Publishing, Paris, 122 p.; http://globalgeochemicalbaselines.eu.176-31-41-129.hs-servers.gr/datafiles/file/Blue_Book_GGD_IGCP259.pdf.

Figure 1. Geochemical maps showing the distribution of Li in (a) GEMAS agricultural soil (hot aqua regia extraction); (b) FOREGS floodplain sediment (total), and (c) EGG bottled mineral water; (d) Li mineral deposit map from the ProMine Mineral database (http://minerals4eu.brgm-rec.fr/); pale yellow indicates the 26 countries covered by FOREGS, and darker yellow the additional 6 countries covered by GEMAS (Albania was covered by FOREGS but not by GEMAS).

De Vos, W., Tarvainen, T. et al.., 2006. Geochemical Atlas of Europe. Part 2 - Interpretation of Geochemical Maps, Additional Tables, Figures, Maps, and Related Publications. Geological Survey of Finland, Espoo, 618 p; http://weppi.gtk.fi/publ/foregsatlas/. EGS GEG, 2008. EuroGeoSurveys geochemical mapping of agricultural and grazing land in Europe (GEMAS) – Field manual. Geological Survey of Norway, Trondheim, NGU report 2008.038, 46 p.; http://www.ngu.no/upload/Publikasjoner/Rapporter/2008/2008_038.pdf. European Commission, 2017. Study on the review of the list of Critical Raw Materials: Criticality assessments. Brussels, 13.9.2017, COM(2017) 490 final; 92 p.; http://doi.org/10.2873/876644. Reimann, C. and Birke, M. (Editors), 2010. Geochemistry of European Bottled Water. Borntraeger Science Publishers, Stuttgart, 268 p.; http://www.schweizerbart.de/publications/detail/artno/001201002#. Reimann, C., Birke, M., Demetriades, A., Filzmoser, P., O'Connor, P. (Eds.), 2014a. Chemistry of Europe's agricultural soils (A): Methodology and interpretation of the GEMAS dataset. Geologisches Jahrbuch, Schweizerbarth, Stuttgart, 528 p. Reimann, C., Birke, M., Demetriades, A., Filzmoser, P., O'Connor, P. (Eds.), 2014b. Chemistry of Europe's agricultural soils (B): General background information and analysis of the GEMAS dataset. Geologisches Jahrbuch, Schweizerbarth, Stuttgart, 352 p. UNEP, 2009. Critical metals for future sustainable technologies and their recycling potential. UNEP, DTI/1202/PA, Paris, 81 p. Salminen, R., Tarvainen, T. et al., 1998. FOREGS Geochemical Mapping Field Manual. Geological Survey of Finland, Espoo, Guide 47, 36 p.; http://tupa.gtk.fi/julkaisu/opas/op_047.pdf. Salminen, R. et al., 2005. Geochemical atlas of Europe. Part 1 – Background information, methodology and maps. Geological Survey of Finland, Espoo, 525 p.; http://weppi.gtk.fi/publ/foregsatlas/.

ABSTRACT. Introduction Agricultural soil (Ap-horizon, 0–20 cm) samples were collected from a large part of Europe (33 countries, 5.6 million km2) as part of the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) project (Reimann et al., 2014a, b). The survey area includes a diverse group of soil parent materials with varying geological history, a wide range of climate zones, and landscapes. The chemical composition of soil represents largely the primary mineralogy of the source bedrock, with superimposed effects of the last glaciation, pre- and post-depositional chemical weathering, formation of secondary products such as clays, and element mobility (Négrel et al., 2015), or continental-scale distribution of elements (Reimann et al., 2014a; Ladenberger et al., 2015). Magnesium is the eighth most abundant element in the Earth's upper continental crust (UCC), with an estimated elemental abundance of 14 955 mg/kg (Rudnick and Gao, 2003). Magnesium is essential for all organisms, not toxic under normal circumstances and is a key plant nutrient and essential for photosynthesis in plants. It is used in industry for example, in transport (automotive, aircraft, train), consumer electronics (laptop, mobile phone, tablet), steel industry, titanium and zirconium production, pharmaceutical and agricultural chemical production and medical implants. Magnesium may also be a preferenced material in all light-weight vehicle concepts, hydrogen storage and advanced battery technology but currently, Mg, as alloying element, is essential for the aluminium industry. The worldwide primary magnesium production in 2016 was around 878 Kt, and 85% of global demand was supplied by China. Magnesium’s criticality is not based on geographical lack of raw material in Europe, rather on trade issues, since China’s low-cost production and export policy made primary production in Europe redundant. The last smelter in Europe was closed in 2001, since European based smelters were unable to compete with low-cost Chinese production, and as a result European primary demand depends mainly on import from China. Worldwide demand is expected to increase in the next decade. In particular, the development of R&D technologies could significantly affect the long-term demand for Mg. The overall results of the 2017 criticality assessment, classified critical raw materials with respect to economic importance versus supply risk, identified 26 raw materials as critical (European Commission, 2017), comprising Mg and elements like Sb, Nb and Ge. The demand for ‘critical’ element resources activated all efforts to find new deposits and possibilities to extract them from mines throughout the world. The GEMAS data set offers European scale results for several so-called high-tech elements, and almost all listed on the Critical Raw Materials list by the European Commission (2017). Here, one of the major elements of the UCC, Mg, is used as a test critical element. The geochemical distribution of Mg in agricultural soil of Europe turns out to be a useful starting tool for identifying potential areas for the occurrence of new resources of high-tech elements. Materials and methods Agricultural soil samples were collected in 33 European countries at an average density of 1 site per 2500 km2, covering an area of about 5.6 million km2 (Reimann et al., 2014a, b). The methods for GEMAS sampling, sample preparation and analysis for major and trace elements were described in detail in Reimann et al. (2014a). Agricultural soil (Ap; 2108 samples) was collected from the ploughing layer of an agricultural arable field at a depth of 0–20 cm. Each sample (ca 3.5 kg) corresponds to a composite of five sub-samples taken from the corners and centre of a 10 × 10 m square. All composite samples were sieved to <2 mm, and milled to less than 63 μm for analysis by wavelength dispersive X-ray fluorescence spectrometry (WD-XRF). A series of project standards and replicates of project samples were used to monitor trueness, repeatability and accuracy, detection limits and QC (Reimann et al., 2011). Samples were also investigated using aqua regia and MMI extraction followed by ICP-MS multi element analysis not showed here. Results and Discussion Less than 5% of the 2108 samples of agricultural soil, analysed for Mg by XFR, are lower than the 50 mg/km detection limit. The median for Mg in the Ap samples in Europe is around 5488 mg/kg and the maximum close to 126,638 mg/kg. Compared to the UCC total Mg average, the median Mg concentration, measured by XRF, is substantially lower in the European agricultural soil samples (ratio median Ap/UCC = 0.367); this may suggest a possible overestimation of the UCC value; it may be also an indication of an overall depletion of the important plant nutrient Mg in agricultural soil. The combination plot histogram - density trace one-dimensional scattergram - boxplot (Fig. 2a) shows the Mg univariate data distribution. The one-dimensional scattergram and boxplot highlight the existence of a substantial number of outliers in the Mg distribution. The density trace and histogram are overall symmetrical in the log-scale. Liming and use of Mg fertilisers are the strongest anthropogenic interferences on natural Mg-cycles. Given the major human interference with Mg in agricultural soil, the map of Mg still clearly depicts geological process (Fig 2b). The southern limit of the last glaciation is thus still visible as a concentration break on the map, but the median Mg concentrations between northern and southern Europe are not as contrasted, as for many other elements (Reimann et al., 2014a, b). Basically, areas underlain by limestone (e.g., eastern and southern Spain), dolomite (Alps) and mafic/ultramafic rocks (Hellas, Norway, Finland) appear as large Mg anomalies on the map. The Central Scandinavian Clay Belt is also visible as a Mg anomaly on the map as well as the occurrence of Mg-silicates in northern Europe. Fig. 2. (a) Combination plot of histogram, density trace, one-dimensional scattergram and boxplot of the Mg distribution in European Ap samples following XRF analysis. (2b) map of XRF total Mg concentrations. (2c) Ca/Na versus Mg/Na ratios in Ap samples, average values for the main lithological end-members (Parker, 1967 for basalt, high and low Ca granite, clay, shale, sandstone, carbonate, ultramafic rocks and granodiorite; Négrel et al., 1993 for silicate, carbonate, evaporite).

Soil chemical composition represents to a large extent the primary mineralogy of the source bedrock, with superimposed effects of glaciation, pre- and post-depositional chemical weathering, formation of secondary products such as clays, and element mobility. Therefore, in soil, Mg, like Al and K, is often retained in weathering profiles, while Na and Ca are rapidly leached as dissolved ions. Comparison of Ca and Mg geochemical pattern in relation to general Na distribution in soil allows discrimination between carbonate and silicate parent materials and among various siliciclastic components (low Ca granite, sandstone and ultramafic rocks). With the knowledge that the most important Mg mineral resources are hosted by ultramafic lithologies and their weathering/alteration products (magnesite), carbonate rocks (dolomite) and chemical deposits (carnallite), GEMAS Mg anomalies can be used to look for potential regions for more detailed Mg exploration.

Acknowledgements The GEMAS project is a cooperative project of the EuroGeoSurveys Geochemistry Expert Group with Eurometaux (European Borates Association, European Copper Institute, European Precious Metals Federation, International Antimony Association, International Lead Association-Europe, International Manganese Institute, International Molybdenum Association, International Tin Research Institute, International Zinc Association, The Cobalt Development Institute, The Nickel Institute, The (REACH) Selenium and Tellurium Consortium and The (REACH) Vanadium Consortium), and a number of outside organisations (e.g., Alterra, The Netherlands; Norwegian Forest and Landscape Institute; Research Group Swiss Soil Monitoring Network, Swiss Research Station Agroscope Reckenholz-Tänikon, several Ministries of the Environment and University Departments of Geosciences, Chemistry and Mathematics in a number of European countries and New Zealand; ARCHE Consulting in Belgium; CSIRO Land and Water in Adelaide, Australia). References European Commission, 2017. Study on the review of the list of Critical Raw Materials: Criticality assessments. Brussels, 13.9.2017, COM(2017) 490 final, 92 pp. Ladenberger, A., Demetriades, A., Reimann, C., Birke, M., Sadeghi, M., Uhlback, J., Andersson, M., Jonsson, E., the GEMAS Project Team, 2015. GEMAS: Indium in agricultural and grazing land soil of Europe – its source and geochemical distribution patterns. Journal of Geochemical Exploration 154, 61–80. Négrel, Ph., Allègre, C.J., Dupré, B., Lewin, E. 1993. Erosion sources determined from inversion of major, trace element ratios and strontium isotopic ratios in river water: the Congo Basin case. Earth and Planetary Sciences Letters 120, 59-76. Négrel, Ph., Sadeghi, M., Ladenberger, A., Reimann, C., Birke, M., the GEMAS Project Team, 2015. Geochemical fingerprinting and sources discrimination in soils and sediments at continental scale. Chemical Geology 396, 1-15. Parker, R.L., 1967. Composition of the Earth's crust. U.S. Geological Survey Professional Paper 440-D, 17 pp. Reimann, C., Demetriades, A., Eggen, O.A., Filzmoser, P., 2011. The EuroGeoSurveys GEochemical Mapping of Agricultural and grazing land Soils project (GEMAS ): Evaluation of quality control results of total C and S, total organic carbon (TOC), cation exchange capacity (CEC), XRF, pH, and particle size distribution (PSD) analysis. NGU Report no. 2011.043, 90 pp. Reimann, C., Birke, M., Demetriades, A., Filzmoser, P., O'Connor, P. (Eds.), 2014a. Chemistry of Europe's agricultural soils (A): Methodology and interpretation of the GEMAS dataset. Geologisches Jahrbuch, Schweizerbarth, Stuttgart, 528 pp. Reimann, C., Birke, M., Demetriades, A., Filzmoser, P., O'Connor, P. (Eds.), 2014b. Chemistry of Europe's agricultural soils (B): General background information and analysis of the GEMAS dataset. Geologisches Jahrbuch, Schweizerbarth, Stuttgart, 352 pp. Rudnick, R.L., Gao, S., 2003. Composition of the Continental Crust. In: Holland, H.D., Turekian, K.K. (Eds-in-chief), Treatise on Geochemistry Volume 3: Rudnick, R.L. (Ed.), The Crust. Elsevier-Pergamon, Oxford, 1-64.

ABSTRACT. European wide data on arsenic concentrations in agricultural soils, waters and crops (AgriAs project) Timo Tarvainen1, Tarja Hatakka1 and Kirsti Loukola-Ruskeeniemi1 (1) Geological Survey of Finland, P.O.Box 96, 02151 Espoo, Finland, timo.tarvainen@gtk.fi

Arsenic is a toxic and carcinogenic substance. According to WHO, the greatest threat to public health from arsenic originates from contaminated groundwater. Food is another notable pathway for As exposure in humans. There are numerous arsenic-related publications and reports, but many of them focus on arsenic problems in South-East Asia or are limited to groundwater or contaminated soil. The AgriAs project (http://projects.gtk.fi/AgriAs/index.html; Water-JPI 2017) has focused on European data on agricultural soils and the quality of related surface water and groundwater. The AgriAs project has summarized European-wide databases and publications on As concentrations in soil and water. This was followed by a literature review and a questionnaire on national-level data sources of As concentrations in agricultural soil and water. A web-based AgriAs questionnaire on national and large-scale regional data sources on arsenic in soil, surface water, groundwater and crops in Europe was sent to 23 countries. The general findings concerning As concentrations in crops were summarized from the literature. Following the assessment of data availability, a list of major data gaps was reported. Reimann et al. (2009) have provided a comprehensive summary of the European-wide availability of data on As concentrations in soil and water. More up-to-date information on national and regional data sources were identified from the AgriAs questionnaire. The questionnaire revealed that regional-scale data are available on arsenic concentrations in soil and surface water. These data can provide a detailed insight into the European-wide anomalies found in the FOREGS (Salminen et al. 2005), Baltic Soil Survey (Reimann et al. 2003), GEMAS (Reimann et al. 2015; Tarvainen et al., 2015) and LUCAS surveys (Tóth et al. 2015a; 2015b). There are quite extensive European-wide datasets on As concentrations in agricultural soil, but more detailed regional mapping at the national level is needed, especially in those areas where anomalously high As concentrations in topsoil have been discovered. According the AgriAs questionnaire and literature study, European-wide data as well as nationwide data on As concentrations in crops are entirely lacking. There is no up-to-date map of arsenic concentrations in European groundwater related to agricultural sites. European-wide or large-scale regional databases very seldom combine arsenic concentrations in agricultural topsoil with concentrations in adjacent surface water or groundwater. According to the European-wide soil geochemical data, two study sites of the AgriAs project in Verdun, France and in Freiberg, Saxony, Germany represent anomalous As areas (Fig. 1). Arsenic anomalies can be either geogenic or anthropogenic, or the anomalies can be a combination of naturally high arsenic concentration and long history of mining and metallurgy like the study site in Freiberg. The study site near Verdun, France, represents anthropogenic anomaly: it is a chemical ammunition breaking-down facility of the interwar period converted into agricultural land. Thus the two test sites can be used to develop and demonstrate the objectives of the AgriAs project: develop recommendations/guidelines for sustainable management of arsenic risks together with stakeholders; to demonstrate arsenic removal technologies in Verdun and Freiberg to assess their technological and economic feasibility; and apply biological tools to manage ecological, environmental and human risks.

Figure 1. Geochemical map showing the distribution of As in GEMAS agricultural soil (hot aqua regia extraction) and the AgriAs project study sites in Verdun, France and in Freiberg, Saxony, Germany. Acknowledgements AgriAs is co-funded by EU and the Academy of Finland, L’Agence nationale de la recherché (France), Bundesministerium für Ernährung und Landwirtschaft (Germany) and Forskningsrådet FORMAS (Sweden) under the ERA-NET Cofund WaterWorks2015 Call. References Reimann, C., Siewers, U., Tarvainen, T., Bityukova, L., Eriksson, J., Gilucis, A., Gregorauskiene, V., Lukashev, V., Matinian, N.N. & Pasieczna, A. 2003. Agricultural Soils in Northern Europe: A Geochemical Atlas. Geologisches Jahrbuch, Sonderhefte, Reihe D, Heft SD 5, Schweizerbart'sche Verlagsbuchhandlung, Stuttgart: 279p. Reimann, C., Matschullat, J., Birke, M. & Salminen, R. 2009. Arsenic distribution in the environment: The effects of scale. Applied Geochemistry 24, 1147–1167. Reimann, C., Birke, M., Demetriades, A., Filzmoser, P. & O'Connor, P. (eds.) 2015. Chemistry of Europe's Agricultural Soils. Part A: Methodology and Interpretation of the GEMAS Data Set. Geologisches Jahrbuch Reihe B Heft 102. 523 p. Salminen, R. (Chief-Ed.), Batista, M.J., Bidovec, M. Demetriades, A., De Vivo, B., De Vos, W., Duris, M., Gilucis, A., Gregorauskiene, V., Halamic, J., Heitzmann, P., Lima, A., Jordan, G., Klaver, G., Klein, P., Lis, J., Locutura, J., Marsina, K., Mazreku, A., O’Connor, P.J., Ols-son, S.Å., Ottesen, R.-T., Petersell, V., Plant, J.A., Reeder, S., Salpeteur, I., Sandström, H., Siewers, U., Steenfelt, A., Tarvainen, T., 2005. Geochemical Atlas of Europe. Part 1 – Background Information, Methodology and Maps. Geological Survey of Finland, Espoo, Finland. Tarvainen, T; Birke, M.; Reimann, C.; Ponavic, M. & Albanese, S. 2015. Arsenic anomalies in European agricultural and grazing land soil. Pages 81 – 88 in: C. Reimann, M. Birke, A. Demetriades, P. Filzmoser & P. O'Connor (eds.) Chemistry of Europe's Agricultural Soils. Part B: General Background Information and Further Analysis of the GEMAS Data Set. Geologisches Jahrbuch Reihe B Heft 103. 352 p. Tóth, G. Hermann, T., Szatmári, G. & Pásztor, L. 2015a. Maps of heavy metals in the soils of the European Union and proposed priority areas for detailed assessment. Science of the Total Environment Tóth, G., Hermann, T., Da Silva, M.R. & Montanarella, L. 2015b. Heavy metals in agricultural soils of the European Union with implications for food safety. Environment International. Water-JPI (2017) Water JPI, Challenges for a changing world. http://www.waterjpi.eu/index.php?option=com_content&view=article&id=79&Itemid=686

ABSTRACT. The Geological Survey of Finland (GTK) has experience in geochemical mapping on a continental scale, a national scale, a regional scale and even on a local scale within urban areas. Since 2016, GTK has carried out soil geochemical baseline mapping around mining areas. A large Ni anomaly related to greenstone belt can be detected on the European scale and the national scale geochemical maps in Finnish Lapland. In the European-wide FOREGS map and on the regional scale geochemical map, the Ni concentrations in subsoil within the anomaly zone of Finnish Lapland are 40 – 100 mg/kg. In 2016, GTK took soil samples of 35 sites of the Kevitsa Ni mining area surroundings. The Ni concentrations were 18 – 228 mg/kg in subsoil and the calculated upper limit of baseline variation for Kevitsa mining area surroundings was 110 mg/kg. Thus, even the European-wide geochemical map provided a good estimate for the soil geochemical baseline for this anomalous zone. However, the much higher concentrations of potentially harmful elements have been found on the local scale baseline mapping around other mining area surroundings which are not so clearly detected on a European scale.

ABSTRACT. Thallium (Tl) is considered as toxic for human and animal organisms, microorganisms and plants (Peter and Viraraghavan 2005; Karbowska 2016). Thallium is redox active and has two oxidation states (Tl1+ and Tl3+), while Tl1+ is believed to be the most common in Tl minerals (Xiong, 2007; George et al., 2019);and, monovalent Tl (Tl1+), that is believed to be the most common in Tl minerals (Xiong, 2007; George et al., 2019), is very mobile, and potentially released into the environment under a range of physicochemical conditions, being easily transported in aqueous form due to its high solubility (Peter and Viraraghavan, 2005). Recent studies of terrestrial ore deposits have demonstrated the ability of pyrite to host concentrations from a few ppm up to weight percent (e.g. ≤3.5 wt%) levels of thallium (Tl) (Zhou et al., 2005; D’ Orazio et al. 2017; George et al., 2018; 2019; Muntean et al., 2011). Regardless its potential to release Tl into the environment under a range of physicochemical conditions, the speciation of Tl in pyrite is not very well understood. Metal incorporation in pyrite is complex (e.g., Deditius et al., 2014; Deditius and Reich, 2016), and it has not been evidently shown whether Tl enters the crystal structure of pyrite or tends to occur as micro- to nano-particles of Tl-bearing phases. It has been suggested that the occurrence of Tl+ in pyrite is coupled with the presence of Sb3+ and As3+. More specifically, the occurrence of Tl into As-pyrite (Tl+-bearing nanoparticles or structurally bound Tl) is strongly reliant on As contents, (Deditius and Reich, 2016); moreover, Tl+ can be lattice-bound in pyrite by a simple coupled heterovalent substitution, i.e. 2Fe2+ ↔ Tl+ + Sb3+ (D’ Orazio et al. 2017; George et al., 2018). However, more recent studies (George et al., 2019) have questioned the model of a coupled Tl+ and Sb3+ substitution, suggesting that Tl+ could occur in structural defects in pyrite. Understanding the pathways and processes of the mineralogical sequestration of Tl and other minor elements (e.g. As, Sb, Hg etc) is key to economic factors in SMS environmental impact, as well as prospecting and extraction; consequently investigation is required of how the minor elements (e.g. Tl, As, Sb) are distributed among key ore minerals and accessory SMS phases, and how this distribution is changed during precipitation, later recrystallization (dissolution–reprecipitation), and seawater weathering (halmyrolysis). The Kolumbo shallow submarine arc-volcano, located in the 5 Ma-to-present Hellenic Volcanic Arc (HVA) in Greece, hosts an active hydrothermal system currently forming polymetallic SMS mineralization, the only known SMS deposit associated with continental margin volcanism (Kilias et al., 2013). Polymetallic sulfide-sulfate (barite) chimneys are uniquely enriched in Tl (avg.: 510 ppm; max.: >1,000 ppm) and Sb (avg.: 8,330 ppm, max.: 2.2 wt. %) (±Hg, As, Au, Ag, Zn). The maximum concentrations of Kolumbo Tl (>1,000 ppm), are the highest reported from modern SMS deposits located on arc volcanoes, which rarely exceed 100 ppm (Monecke et al., 2016). Consequently, Kolumbo is an ideal natural laboratory to investigate the deportment of potentially toxic Tl (and other metal contaminants, As, Sb) in the Aegean Sea. The studied sulfide-sulfate chimneys exhibit concentric mineral zones formed at successive stages of chimney growth (Kilias et al., 2013): a lithified inner sulfide-sulfate core (ISSC) mantled by an outer As-sulfide layer (OAsL), which in turn is covered by a Fe-rich crust (SFeC) (Kilias et al., 2013). Pyrite is the dominant sulfide mineral in the ISSC, followed by marcasite, sphalerite, galena, Sb-Pb-sulphosalts, and minor, chalcopyrite, anglesite, Al-silicates, and Sb-Zn-sulfosalts. The OAsL consists chiefly of amorphous orpiment (As2S3)-like, and realgar (AsS)-like As-sulfides, stibnite, and Pb-Sb (-As) sulphosalts, in a barite matrix, and rare opal; the OAsL is overgrown by amorphous ferrhyhidrite-like Fe-oxyhydroxides (SFeC). Here we report LA-ICP-MS trace metal(loid) analyses and maps showing the concentration, distribution and zonation of Tl, Au, As, Sb, and Mo in: (1) primary colloform-crustiform and moss textured pyrite (Py 1–up to: 131 ppm Au, 5870 ppm As, 64600 ppm Sb, 22 ppm Mo and 10140 ppm Tl); (2) later recrystallized (dissolution–reprecipitation) fine-grained pseudobladed pyrite (Py 2–up to:65 ppm Au, 13290 ppm As, 36100 ppm Sb, 7.8 ppm Mo and 2390 ppm Tl); (3) euhedral zonal pyrite (Py 3–up to: 54 ppm Au, 17870 ppm As, 11580 ppm Sb, 2.2 ppm Mo and 1163 ppm Tl), and, (4) sphalerite(Sph) (up to:40 ppm Au, 3920 ppm As, 29700 ppm Sb, 12.1 ppm Mo and 7470 ppm Tl), from the ‘‘inner” ISSC zone; and, (5) colloform pyrite (Py1A– up to: 58.3 ppm Au, 7930 ppm As, 10.63 ppm Mo, 46800 ppm Sb and 1661 ppm Tl); (6) orpiment (As2S3)-type As-rich sulfides (“As2S3“)(up to: 861 ppm Au, 90 ppm Mo, 12300 ppm Sb and 82200 ppm Tl); (7) stibnite (Stb) (up to: 64 ppm Au, 21800 ppm As, 94 ppm Mo and 21800 ppm Tl); and, Sb-Pb sulfosalts (up to: 89.5 ppm Au, 6550 ppm As, 14 ppm Mo and 1381 ppm Tl) from the “outer” OAsL, zone. Ablation profiles for As, Sb, Tl, and Au can be either irregular or smooth, indicating both lattice substitutions and nanoparticle inclusions (e.g. George et al., 2019). ISSC pyrite and sphalerite, are particularly rich in Tl (≤10140 ppm, Py1; ≤2390 ppm, Py2; ≤1163 ppm, Py3; 7470, Sph), Sb (≤64600 ppm, Py 1; ≤29700 ppm), and As (≤ 17870 ppm, Py 3; 3920 ppm), and Stb in Tl (≤21800 ppm) and As (≤21800 ppm); Au may be present above 100 ppm in Py 1(≤131 ppm), and above 800 in “As2S3“ (≤861 ppm), and Mo may be present above 20 ppm in Py1 (≤22 ppm), As2S3 (≤90 ppm) and Stb (≤94 ppm). LA-ICP-MS analyses show good correlation of Tl and Sb (R2 = 0.52) in Py1, and Tl and Mo in Py1 (R2 = 0.86) and Py2 (R2 = 0.82) and Py1A (R2 = 0.57), and, Sb and Au in sphalerite (R2 = 0.76), and, Tl and As in stibnite (R2 = 0.52). Concentrations of Au, Sb, Mo and Tl drop significantly from Py1 to Py3, and further to Sph, in the ISSC, while, in the OAsL the opposite trend is observed, i.e. Au is increased in Py1A and “As2S3“, and, Mo and Tl are enriched in “As2S3“and stibnite, compared to the respective ISSC sulfide phases; Sb is generally comparatively decreased in the OAsL. Trace element mapping using LA ICP MS of colloform Py1 reveals a marked compositional zoning with respect to Tl, As, Sb, Au and Mo (also Pb and Ag). Based on the LA ICP MS mapping, Tl shows no clear correlative relationship with Au or As, but only with Sb and Mo. This is supported by interelement Tl vs Au, and Tl vs As trends, which show no correlation (R2 = 0.20 R2 = 0.13, respectively).

Our findings suggest that: 1. During the growth of each zone sequence, i.e. ISSC, OAsL, sulfide assemblages and their trace elements are modified by i.e. redox processes, overprinting fluids, recrystallization, exsolution of metastable phases, or boiling, during initial precipitation and later recrystallization (a dissolution–reprecipitation process); as a result a large proportion of these elements (Au, Sb, Mo and Tl) are expelled possibly as composite nano-particles (George et al., 2019), causing a zone refinement of the metals present in the various formed chimney minerals, strongly supporting zone refinement to be indispensable for polymetallic chimney growth, at Kolumbo. 2. Observed decoupled behavior between Tl, and Au and As, and, coupled behavior between Tl and Sb (at least in colloform Py1), contradicts the paradigm of strong dependence of Tl uptake on As and Au contents of pyrite (Deditius and Reich, 2016), as it has also been before documented for Au and Cu, for the Kolumbo SMS mineralization (Santoro et al., 2018). In addition, statistically significant coupled behavior exists between Tl and Mo in Py1 and Py2. 3. The incorporation of Tl into colloform pyrite seems to be facilitated by the presence of Sb, and not As that generally facilitates Au incorporation (Santoro et al., 2018) in the Kolumbo hydrothermal vent system. Our results corroborate that Tl is possibly incorporated in Py1 mainly in in micro- to nanoparticles (NPs) of other Tl-bearing phases, possibly Tl-stibnite, with important implications from an economic and environmental point of view.

Acknowledgements The “SeaBioTech” EU-FP7 project (Grant No. 311932) is thanked for funding the sampling.

References Deditius, A.P., Reich, M., 2016. Constraints on the solid solubility of Hg, Tl, and Cd in arsenian pyrite. Am. Mineral. 101, 1451–1459. Deditius, A.P., Reich, M., Kesler, S.E., Utsunomiya, S., Chryssoulis, S.L., Walshe, J., and Ewing, R.C., 2014. The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits. Geochimica et Cosmochimica Acta 140, 644–670. D’Orazio, M., Biagioni, C., Dini, A., Vezzoni, S., 2017. Thallium-rich pyrite ores from the Apuan Alps, Tuscany, Italy: constraints for their origin and environmental concerns. Miner. Depos. 52, 687–707. George, L.L., Biagioni, C., D’Orazio, M., Cook, N.J., 2018. Textural and trace element evolution of pyrite during greenschist facies metamorphic recrystallization in the southern Apuan Alps (Tuscany, Italy): initiation of Tl-rich sulphosalt melt formation. Ore Geol. Rev. 102, 59–105. George, L.L., Biagioni, C., Lepore, G.O., Lacalamita, M., Agrosì, G., Capitani, G.C., Bonaccorsi, E. and 'Acapito, F., 2019. The speciation of thallium in (Tl, Sb, As)-rich pyrite. Ore Geol. Rev. 107, 364–380. Karbowska, B., 2016. Presence of thallium in the environment: sources of contaminations, distribution and monitoring methods. Environmental monitoring and assessment 188(11), 640. Kilias, S., P. et al. 2013. New insights into hydrothermal vent processes in the unique shallow-submarine arc-volcano, Kolumbo (Santorini), Greece. Sci. Rep. 3, 2421; DOI:10.1038/srep02421. Large, R.R., Maslennikov., V. V., Robert, F., Danyushevsky, L.V., Chang,Z., 2007. Multistage sedimentary and metamorphic origin of pyrite and gold in the Giant Sukhoi Log deposit, Lena Gold Province, Russia. Econ. Geol. 102, 1233–1267. Monecke, T. et al., 2016. The minor element endowment of modern sea-floor massive sulfide deposits and comparison with deposits hosted in ancient volcanic successions. Rev. Econ. Geol. 18, 245–306. Muntean, J.L., Cline, J.S., Simon, A.C. and Longo, A.A., 2011. Magmatic–hydrothermal origin of Nevada’s Carlin-type gold deposits. Nature Geoscience 4(2), 122. Peter, A.L.J., Viraraghavan, T., 2005. Thallium: a review of public health and environmental concerns. Environ. Int. 31, 439–501. Santoro, L. et al., 2018. LA-ICP-MS evidence for coupled geochemistry of Au, Cu and As in As-pyrite from modern sea-floor massive sulphides, Kolumbo arc-volcano, Greece. Abstracts from the 2017–2018 Mineral Deposits Studies Group meeting, Applied Earth Science, 127:2, 46-79, DOI: 10.1080/25726838.2018.1487425. Xiong, Y., 2007. Hydrothermal thallium mineralization up to 300 °C: a thermodynamic approach. Ore Geol. Rev. 32, 291–313. Zhou, T.F., Fan, Y., Yuan, F., Wu, M.A., Hou, M.J., Voicu, G., Hu, Q.H., Zhang, Q.M., Yue, S.C., 2005. A preliminary geological and geochemical study of the Xiangquan thallium deposit, eastern China: the world’s first thallium-only mine. Mineral. Petrol. 85, 243–251.

ABSTRACT. Introduction The thrust belt in the Balkan Peninsula along the margin of the Apulian foreland is known as the External Hellinides in Greece,which has been divided into three tectonostratigraphic zones which are from east to west: the Gavrovo Zone, the Ionian Zone and the Pre-Apulian (or Paxoi) Zone. The rock successions in these zones consist of Mesozoic and Cenozoic strata, which have been thrust westwards onto the Apulian foreland. Form Eocene to Miocene, the migrating internal Hellinide orogeny to the west caused the simultaneous migration and the compressional deformation of the foreland in front of the orogen. (Underhill, 1985; Karakitsios, 1995; Karakitsios and Rigakis, 2007; Karakitsios, 2013) The major structural trends are recognized in Western Greece. In the first place, major thrust fault trend NNW-SSE. These are locally offset by east-west oriented faults, some of which, such as those in the Gulf of Corinth, may have been inherited from Early Mesozoic rifting (Robertson et al., 1991). In the Cenozoic, they acted either as wrench faults during thrusting (e.g. the Petoussi Fault) or as basin bounding normal faults (e.g. in the Gulf of Patras). Thirdly, a series of dextral NE-SW trending strike-slip faults are presented in Cephalonia fault in the South. These strike-slip faults appear to have taken up relative motion in the Neogene between the Anatolian-Aegean Plate and the African-Apulian Plate north of the Hellinides subduction zone (Walcott and White, 1998).

Materials & Methods For the purpose of this study, a detailed investigation has been made in the Ionian zone. Six sections have been studied, and 150 samples collected in order to make extended laboratory analyses. The reservoir parameters that examined are porosity and permeability through a Accupyc 1330 pycnometer and a Geopyc 1360, from Micrometrics respectively. Furthermore, thin sections have been constructed in order to verify the sedimentological characteristics of the involved carbonate rocks.

Results The principal lithofacies of Section F (Louros Section) is biolithitic (boundstone). Section B (Perivleptos Section) is characterized by the lithofacies biosparite (grainstone). The Pantokrator limestones give evidence of a depositional environment characterized by a carbonate platform with characteristics of both intertidal and subtidal settings. Vadose diagenesis of some redeposited carbonate clasts points a partly subaerial exposure. Section E (Vigla Section) consists of radiolarian biomicrite (wackestone) characterizing a low energy deep environment. In Section A (Koloniati Section), pisoid lithoface, is the only distinguished from all the other lithofacies. Pisoids have been described in the classical paper of Dunham (1962) and interpreted as caliche soil pisoids formed by subaerial vadose diagenesis during episodic lowstands of sea level. The range of depositional interpretations of these pisoids includes caliche formation in continental or coastal-spray-zone, supratidal settings, vadose-marine inorganic precipitation in inter and subtidal environments of formation in marine seepage or groundwater springs (Flugel, 2010). Within this section, the following lithofacies have been observed as well: biomicrite (mudstone-wackestone) which refers to deep depositional environment. In Section D (Asprageli-2 Section), the following three lithofacies have been observed: bioclastic (packstone), which represents a medium energy environment. Possibly, sediments have been transported within the basin from the platform, biomicrite (wakestone-packstone-floatstone) with plaktonic foraminifera, deposited in a medium energy pelagic depositional environment and biolithitic (bounstone) corresponding to the margin of the platform. In Section C (Asprageli-1 Section) the lithofacies that have been identified is biomicritic (packstone). Within this lithofacies pelagic foraminifera have been observed, that represent a medium energy environment, possibly corresponding to a deep depositional environment. Although it is natural to assume that permeability values depend on porosity, it is not simple to determine which is the appropriate relationship since this would require a detailed knowledge of size distribution and spatial arrangement of the pore channels in the porous medium. Generally, it is known that the higher the porosity, the higher permaebility we should have. However, because of the complexity and the large number of related parameters no simple single functions can exist. In our samples, it has been observed that as the porosity increases the permeability values seem to decrease. For instance, in Section E (Vigla Section), sample B3 with porosity 6,85% has higher permeability value (2,7017) than sample B10 which presented a higher porosity value (23,1%) but a lower permeability measurement (2,6811). This principle can be observed in several samples within our study area. For section F, the average porosity is 3,92%, while permeability values range between 2,6496 (sample Λ45) and 2,7319 (sample Λ25). For Section B the average porosity is 8,46%. According to the permeability measurements, for Section B, range between 2,6496 (sample Π18) and 2,7319 (sample Π12). For Section E the average porosity is 8,67%. For the permeability measurements, sample B1 showed the highest value (2,7277), while sample B10 showed the lowest value (2,6811). The average porosity from section’s A samples is 7,57%. On the other hand, permeability measurements range between 2,6707 (sample Κ28) and 2,718 (sample Κ8). For Section D the average porosity is 11,59%. Permeability values, for Section D, range between 2,6204 (sample A29) and 2,7411 (sample A24). For Section C the average porosity is 6,29%. The highest porosity value has been reported in sample A1 (16,88%) and the lowest value within the sample A13 (2,50%). For the permeability measurements, the highest value presented in sample A23 (2,7193), while the lowest appeared within sample A3 (2,5799).

References Dunham, R.J., 1962. Classification of Carbonate Rocks According to Depositional Texture. In W.E. Hamm (ed.), Classification of Carbonate Rocks, A Symposium, American Association of Petroleum Geologists, p. 108-121. [Journal Article] Flugel, E., 2010. Macrofacies of Carbonate Rocks. Springer-Verlag Berlin Heilderberg. [Book] Karakitsios, V., 1995. The influence of preexisting structure and halokinesis on organic matter preservation and thrust system evolution in the Ionian basin, northwestern Greece: AAPG Bulletin, vol. 79, p. 960–980. [Journal Article] Karakitsios, V., and Rigakis, N., 2007. Evolution and petroleum potential of western Greece: Journal of Petroleum Geology, vol. 30, no. 3, p. 197–218. [Journal Article] Karakitsios, V., 2013. Western Greece and Ionian Sea petroleum systems. AAPG Bulletin, vol. 97, no. 9, p. 1567-1595. [Journal Article] Robertson et al., 1991. Paleogeographic and paleotectonic evolution of the Eastern Mediterranean Neotethys. Paleogeography, Paleoclimatology, Paleoecology. 87, p. 289-343. [Journal Article] Underhill, J.R., 1985. Neogene and Quaternary tectonics and sedimentation in Western Greece. Ph.D Thesis. University of Wales, Cardiff. [Dissertation] Walcott, C.R. and White, S.H., 1998. Constraints on the kinematics of post-orogenic extension imposed by stretching lineations in the Aegean region. Tectonophysics, 298, p. 155-175. [Journal Article]

ABSTRACT. The field observations of the Lower Cretaceous “Vigla formation” in NW Peloponnesus (Gianniskari beach) and according to Bourli et al., (2019), indicate a fault-controlled formation that was accumulated into restricted basins. These basins were formed from normal faults with NNW-SSE direction and were influenced from ENE-WSW directed transfer faults. According to Bourli et al., 2019 the subdivision of the Ionian basin into asymmetric grabens resulted in variations in geometry and water depth and thus, sedimentary successions with different thicknesses were accumulated. The deeper deposits occur in the central part of each asymmetric graben, where the “Vigla shales” were deposited. The Lower Cretaceous “Vigla formation”, along the Gianiskari beach consists of two different members, the lower one made of “Vigla limestones” and the upper one made of strongly deformed “Vigla shales”. Vigla shales consist of thinly interbedded chert and shales, up to 60 m thick. The chert is mostly reddish but is also black or green, that characterizes in general cherts. Synsedimentary faults produced slumping within Vigla shales, during sedimentation. This slumping is up to 30m long and up to 40cm relief high. Synsedimentary faults have a general southward direction and strong deformation internally to the deposits. Finally, some of the faults produced also flower structures producing accommodation space that was filled up by successive deposits. Geochemical analysis in 31 samples with Rock-Eval VI, from the up to 60m thick succession, showed that there are at least eight (8) samples with more or close to 0.50% TOC (Table 1). From these results and according to the analytical restriction (when S2 is <0.2 then Tmax is not considered accurate), we concentrate on the Tmax values of three samples (G1R, G4 and G5).They indicate that the contained organic matter is immature. Although there are samples with high enough TOC content, the respective S1 and S2 values are very low. The visual inspection of the FID pyrolysis signals of the samples revealed a wide pattern of the S2 peak in most samples, without a clear maximum point. In several samples two different distributions may be identified within the S2 peak, corresponding to immature and over-mature organic matter. These distributions are shown for the samples G10 and G30 in Fig. 2. The presence of the over-mature kerogen may be attributed to transported reworked material before deposition in the current location. The low concentration of kerogen in the studied samples does not allow for the reliable determination of its origin and therefore a more detailed study is advisable to reveal the sedimentation history of the studied Vigla shales samples. Considering the above results and taking into account that Vigla shales are proposed as one of the possible sources for hydrocarbon production in the Ionian basin, further studies are needed to document their real hydrocarbon generation potential.

ABSTRACT. Background The eastern Mediterranean region has long been a region of interest concerning palaeoclimatic (Kaniewski et al., 2013; Triantaphyllou et al., 2014) and palaeoenvironmental (Pavlopoulos et al., 2012; Kouli et al., 2012; Avramidis et al., 2017) studies, due to climate heterogeneity and complex atmospheric circulation patterns that produce regional precipitation and temperature fluctuations. Studies of coastal sedimentological environments allow the recognition of coastline changes and give information about the rate of sedimentation, eustatic sea level changes and tectonic movements. Annually laminated lake sediments (varves), have proven to be excellent geoarchivies in order to interpret changes that occurred during the Holocene period, regarding elemental fluxes, palaeoclimate reconstruction, sea level fluctuation, tectonic activity etc. The distinct color, composition, texture structure and thickness, contained in all varve types, corresponds to different climatic driven mechanisms. Thus, the study of varved sedimentary records, can provide annually to seasonal climatic variations and mirrors sedimentological and environmental conditions taking place in the catchment. Objectives The study area is located at the east part of the Gulf of Corinth, an active rift and one of the most seismically active regions in the world. Until the 19th century, when an artificial channel was opened, lake Vouliagmeni lake completely separated from the sea. Anoxic conditions seem to prevail throughout the year, at least below 38 m water depth. Human occupancy in the area, as indicated from archaeological findings in the area, is recorded during the Bronze Age (3100-1700 BC) and Early Iron Age (1075-750 BC). The aim of the present study is the high-resolution analysis of a 6m varved core retrieved from Vouliagmeni lake, covering the last ~12000 years, in order to extract regional and long scale palaeoclimatic data. Methods Standard sedimentological analysis was conducted on 90 samples, including grain size analysis, Total Organic Carbon (TOC) and Calcium Carbonate content. For the X-ray Diffraction (XRD) analysis, a Brucker D8 device was used. XRF core log analysis was performed with a step of 0.5 cm, at the Institute of Geosciences at Kiel University (Germany), using an Avaatech system. Core scanning was performed with a Molybdenium tube set at 10 kV and 30 kV with an integration time of 60 second per measurement. The chronological framework of the core was determined by 8 AMS 14C radiocarbon dating, combined with laminae counting. For the exact determination of each lamination boundaries as well as an estimation of the bulk density throughout the core, CT scanning was performed, at General University Hospital of Patras in Greece. Results Through varve counting in the sediment core, combined with the AMS radiocarbon dating, the accumulation rates in the study area seem to change at around 3 ka BP (Fig. 1). Varved sediments interrupted by non laminated silty clay sequences were recognized in all core Units. Calcite rich layers alternating with organic rich layers, correspond to summer and winter depositions. Varve thickness was determined through the CT scan models that were produced for the core and was used as a seasonal intensity interval. Representative elemental ratios were constructed in order to recognize the different sedimentary processes taking place in the study area (Fig. 1). Some long-scale climatic events (8.2 ka BP, 6-5 ka BP, 3.2-3.8 ka BP) seem to be well reflected into the elemental composition of the core. Rb/Sr ratio which is a suitable indicator for precipitation/physical erosion in the catchment area, shows distinct climatic driven fluctuations. The aragonite rich laminations that occur in the core, are documented in the Ca/Sr ratio, with increased values distinguishing a terrigenous supply of CaCO3. The S and Pb content were used for marine inundations. Conclusion Vouliagmeni core, presents the oldest geoachive in Greece concerning varved sediments. Sedimentation rate of the study area seems to completely change at around 3000 cal BP and can be strongly associated with the relative sea level change at around that time. Paleoclimatic signals detected through the geochemical analysis conducted in the core, pronounce clear interaction between elemental composition and temperature/precipitation fluctuations. Future analysis and microscale examination especially in the varved sequences, will provide even more details regarding regional climatic fluctuations and will increase the spatial coverage on the already existing palaeoclimatic datasets.

ABSTRACT. The basin of Thermaikos Gulf is located at the Northwestern part of the Aegean Sea, North Greece. It is a tectonic draft with a varying depositional environment, formed as a result of the NNW-SSE trending rifting tectonic movements, which developed in this area during Tertiary. During the Pliocene to Pleistocene, the basement was effected by relatively rapid submergence. Consequently, the appropriate conditions were formed for the transportation and the deposition of sediments within the basin. In the present work, ten (10) samples of borehole cores from the area of the Internal Thermaikos Gulf were studied to examine their mineralogical, textural and lithological features. The samples were examined macroscopically and sieved in ≥2 and <2 mm subsamples. The ≥2 mm pebbles were inspected and characterized by using stereoscope and their textural and morphological characteristics were recorded. The <2 mm subsamples were treated according to Jackson techniques, and sand, silt and clay fractions were measured. The mineralogical composition of these fractions was studied by using X-ray diffraction (XRD). All the methods show that the deposition inside the study area took place in a coastal marine depositional environment, in conjunction with the rapid transportation of the sediments by the rivers and large streams, which leaked mainly through the hydrological basin of Thessaloniki and of Dendropotamos to some extent. The composition of Quaternary clastic materials of the Internal Thermaikos Gulf can be mainly considered as a result of the weathering which took place in the neighboring hydrological basins, where igneous and metamorphic rocks prevail. In addition, boulders of the Tertiary series (mainly from the Red beds) were also found.

ABSTRACT. Background & Methods The studied area of the Ionian Sea and the Western Greece margin, running from the Diapondia Islands-north of Corfu Island, to Filiatra in Southern Peloponnese, is characterized by the most external Hellenides zones and the Apulian Platform. It is well known that during the Tethyan rifting, taphrogenetic processes divided the uniform carbonate platform into shallower parts (the Apulian Platform, its margin the Pre-Apulian zone, and the Gavrovo-Tripolitza Platform) and deeper parts (the Ionian basin). From that time, different sedimentary evolution processes took place in each part, thus the zones exhibit distinct lithostratigraphic columns with different petroleum systems (Karakitsios, 2013). The external Hellenides units are separated by NW-SE trending thrusts. In the offshore areas of the Ionian Sea, a system of NE-SW strike-slip faults cross-cuts the Apulian, Pre-Apulian and Ionian units. The most important of these strike-slip faults is the Kefalonia Transform Fault Zone (KTFZ), dividing the offshore area in two (2) segments; the north and the south segments. For the purpose of this study, eight (8) wells have been selected in order to cover both geographically the three segments and stratigraphically the external Hellenides zones which are present in the area. In the north segment: East Ericoussa-1, Yanadhes-1, Paxos Gaios-1X, and Parga-1; and in the south segment: South Kefallinia-1, Agios Kirikos-1, Sosti-1 and Peristeri-1. A hierarchical approach to sedimentological description and interpretation has been applied to generate the present lithotypes/lithofacies (LTs/LFs) through cuttings and core data. The LTs/LFs have been grouped in bed-set scale units-depositional packages (DPs) with similar characteristics and internal organization. The vertical and lateral organization of the depositional packages can define the bed-set stack scale facies associations (FAs) with specific geometries and dimensions. These facies can be assigned to specific depositional environments. Results & Conclusions The wells which have been drilled on the Ionian zone, exhibit a wide range of both clastic and carbonate depositional environments, ranging from shallow marine, coastal, deltaic, to deep-water (Table 1). On the other hand, the wells which have been drilled on the Pre-Apulian unit, exhibit shallow marine carbonate deposits overlaid by deep-water to shallow-marine clastic sediments. Consequently, the aforementioned depositional environments have their distinct FAs and DPs in different proportions through geological time. The differences between north Segment and south Segment might be due to: • Different isopic domains (Jurassic, Ionian → deep Vs Pre-Apulian → shallow) • Rifting and paleogeography (Cretaceous to Eocene, development of new platforms in the area) • Shallowing (Oligocene-Miocene, relatively shallowing of northern Ionian domain, compared to the southern) • Coverage and well position issues (Oligocene-Miocene, higher coverage from well data in north segment) • KTZ juxtapose of FAs (Pliocene – Pleistocene, juxtaposition of deeper FAs of south segment westwards compared to northern segment) The depositional environments interpretation of this study, confirms the onshore data studies (Karakitsios et al, 2010b; Makrodimitras, 2011; Maravelis et al, 2014;). The available log data can give a first impression of the FAs with the best reservoir properties, such as the upper shoreface, proximal lower shoreface, channel, lobe and shallow shelf deposits. However, the hydrocarbon shows during the drilling program, might range and be present in a wide range of FAs (asterisk * on Table 1). This model confirms previous studies in western Greece areas (Getsos et al., 2007), where Pre-Apulian Zone deposits were assigned to inner carbonate ramp, and external to middle Ionian Zone assigned to middle to outer carbonate ramp conditions. The well data which correspond to inner ramp conditions are the evaporitic, sabkha, lagoonal and tidal flat deposits of Paxos Gaios-1X and South Kefalinia-1. The middle to outer ramp conditions represented by the slope and base of slope deposits, were observed mostly in South Kefalinia-1. The tectonism of the External Hellenides, which is moving to the SW, along with the presence of the major strike slip faults, leads to a juxtaposition of depositions from different geological environments, making them present quite far from the place initially deposited and even further from the source of sedimentation regarding the clastic sediments. Due to the structural setting of the area and the distance between the wells, any attempt to correlate specific FAs among wells is very speculative, leading us to correlate only coeval deposits in terms of age

ABSTRACT. Objectives The late Miocene has been considered as one of the most climatically stable periods of the Cenozoic, characterized by minor long-term cooling and ice growth (Zachos et al., 2001). Especially, the Tortonian-Messinian Transition (TMT) is recognized as a priority for paleoenvironmental reconstruction and climate modelling due to the significant paleoenvironmental changes preceding the Messinian Salinity Crisis (MSC) (Blanc-Valleron et al., 2002; Drinia et al., 2007) and the development of the modern Mediterranean-type climate (Mertz-Kraus et al., 2009) respectively. This time window is of particular importance for the paleoceanographic evolution of the entire Mediterranean Sea, because it covers the successive closure of the marine Mediterranean-Atlantic gateways, which culminated in the onset of the MSC. The basin experienced a dramatic hydrological and biological crisis induced by a powerful combination of geodynamic and climatic drivers (Roveri et al., 2014; Karakitsios et al., 2017a; Krijgsman et al., 2018). The change of the Mediterranean's connections with both the Atlantic Ocean and the freshwater Paratethyan basins, caused high-amplitude fluctuations in the hydrology of its basins (Karakitsios et al., 2017b; Vasiliev et al., 2019), which had a great impact on the subsequent geological history of the Mediterranean area, and on the salinity of the global oceans. The geological expression of this evolution was the omnipresent cyclic marl/sapropel succession because freshwater input was not constant, but strongly pulsed at precessional time-scales (Hilgen et al., 1995). In the present study, we present an integrated study based on sedimentological, micropaleontological, and geochemical data from the pre-evaporitic sedimentary sequence of the Faneromeni section (Crete Island, eastern Mediterranean), which provides an excellent illustration of the progressive restriction of the Mediterranean basin in response to paleoclimate. The observed sedimentary cyclicity corresponds to lithological alternations from laminated to indurated homogeneous marls and clayey limestones, and covers the late Tortonian and earliest Messinian stages (7.6-6.7 Ma; Moissette et al., 2018). Outcropping marine sediments in Crete, which preserve the foraminiferal signal intact, provide windows into the Mediterranean that have not been recovered by deep sea drilling, because the late Miocene sedimentary record from this area is buried under thick layers of salt deposited when the Mediterranean desiccated. Methods The tools used by the Miocene palaeoclimate community have changed over time, and researchers continue to use the most sophisticated and independent techniques available for reconstruction. Proxies have been developed to estimate different aspects of the environment, but surface ocean temperatures and salinities are by far the primary data generated, since together they control ocean water density and thereby thermohaline circulation. Initially, the foraminiferal record was qualitatively evaluated for dissolution by X-ray micro-computed tomography. Stable oxygen (δ18O) and carbon (δ13C) isotopes were also used to estimate salinities, and indirectly ice volume. Moreover, primary temperature proxies, including foraminiferal Mg/Ca and Sr/Ca ratios, were utilized for the paleotemperature reconstruction. Those proxy techniques have strengths and limitations (Kontakiotis et al., 2011, 2016; Antonarakou et al., 2019), but each plays an important role in our conceptual understanding of the late Miocene Earth. The use of multiple proxies is of great benefit to gaining more robust and detailed estimates of the palaeoenvironment as long as the relative limitations of various techniques are recognized. Results We present the first evidence for changes in the upper water column reflected by sea surface temperature (SST) and salinity (SSS) variations that correlate with pronounced paleoclimatic fluctuations. Our planktonic isotope record, in combination with paired mixed layer Sr/Ca-derived SST data, reveal that the very warm late Tortonian interval was followed by a strong long-term cooling and desalination trend (up to 100C and 10‰ respectively) during the earliest Messinian. This change in the upper water column just after the T/M boundary attributed to the paroxysmal phase of the so-called “siphon” event. Especially, the climate shift that occurred at the end of a global carbon isotope decrease suggests that changes in the carbon cycle were instrumental in driving late Miocene climate dynamics (cooling and aridity) in the progressively isolated eastern Mediterranean Sea. The observed salinity variability during that time interval also provides further insights about seasonal freshwater inputs, and gives new support to the much-debated hydrological regime preceding the deposition of evaporites.

Conclusions This study focuses on and further extends the application of the foraminiferal Sr/Ca paleothermometer to late Miocene Mediterranean sections, and inserts the climate history of this setting into the framework of global climate through this time period. Our findings reveal a non-gradual increase in sea surface salinity prior to the onset of the MSC, but substantial variability in response to climatic oscillations, supporting the concept of a stepwise restriction of the Mediterranean Sea. References Antonarakou, A., Kontakiotis, G., Vasilatos, C., Besiou, E., Zarkogiannis, S., Drinia, H., Mortyn, P.G., Tsaparas, N., Makri, P., Karakitsios, V., 2019. Evaluating the effect of marine diagenesis on Late Miocene pre-evaporitic sedimentary successions of eastern Mediterranean Sea. IOP Conference Series: Earth and Environmental Sciences, 221: 012051. [Journal Article] Blanc-Valleron, M.M., PierreI, C., Caulet, J.P., Caruso, A., Rouchy, J.M., Cespuglio, G., Sprovieri, S., Pestrea, S, Di Stefano, E., 2002. Sedimentary, stable isotope and micropaleontological records of paleoceanographic change in the Messinian Tripoli Formation (Sicily, Italy). Palaeogeogr. Palaeoclimatol. Palaeoecol., 185, 255–286. [Journal Article] Drinia, H., Antonarakou, A., Tsaparas, N., Kontakiotis, G., 2007. Palaeoenvironmental conditions preceding the Messinian Salinity Crisis: A case study from Gavdos Island. Geobios, 40, 251–265. [Journal Article] Hilgen, F.J., Krijgsman, W., Langereis, C.G., Lourens, L.J., Santarelli, A., Zachariasse, W.J., 1995. Extending the astronomical (polarity) time scale into the Miocene. Earth Planet. Sci. Lett., 136, 495–510. [Journal Article] Karakitsios, V., Cornée, J.-J., Tsourou, T., Moissette, P., Kontakiotis, G., Agiadi, K., Manoutsoglou, E., Triantaphyllou, M., Koskeridou, E., Drinia, H., Roussos, D., 2017b. Messinian salinity crisis record under strong freshwater input in marginal, intermediate, and deep environments: The case of the North Aegean. Palaeogeogr., Palaeoclimatol., Palaeoecol., 485, 316–335. [Journal Article] Karakitsios, V., Roveri, M., Lugli, S., Manzi, V., Gennari, G., Antonarakou, A., Triantaphyllou, M., Agiadi, K., Kontakiotis, G., Kafousia, N., de Rafelis, M., 2017a. A record of the Messinian salinity crisis in the eastern Ionian tectonically active domain (Greece, eastern Mediterranean). Bas. Res., 29, 203–233. [Journal Article] Kontakiotis, G., Mortyn, P.G., Antonarakou, A., Drinia, H., 2016. Assessing the reliability of foraminiferal Mg/Ca thermometry by comparing field-samples and culture experiments: A review. Geol. Quart., 60 (3), 547–560. [Journal Article] Kontakiotis, G., Mortyn, P.G., Antonarakou, A., Martínez-Botí, M.À., Triantaphyllou, M.V., 2011. Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: core top results from the Aegean Sea (eastern Mediterranean). Geochem. Geophys. Geosyst., 12 (9), Q09004. [Journal Article] Krijgsman, W., Capella, W., Simon, D., Hilgen, F.J., Kouwenhoven, T.J., Meijer, P.Th., Sierro, F.J., Tulbure, M.A., van den Berg, B.C.J., van der Schee, M., Flecker, R., 2018. The Gibraltar Corridor: Watergate of the Messinian Salinity Crisis. Mar. Geol., 403, 238–246. [Journal Article] Mertz-Kraus, R., Brachert, T.C., Reuter, M., Galer, S.J.G., Fassoulas, C., Iliopoulos, G., 2009. Late Miocene sea surface salinity variability and paleoclimate conditions in the Eastern Mediterranean inferred from coral aragonite δ18O. Chem. Geol., 262 (3-4), 202–216. [Journal Article] Moissette, P., Cornée, J.-J., Antonarakou, A., Kontakiotis, G., Drinia, H., Koskeridou, E., Tsourou, T., Agiadi, K., Karakitsios, V., 2018. Palaeoenvironmental changes at the Tortonian/Messinian boundary: A deep-sea sedimentary record of the eastern Mediterranean Sea. Palaeogeogr. Palaeoclimatol. Palaeoecol., 505, 217–233. [Journal Article] Roveri, M., Flecker, R., Krijgsman, W., Lofi, J., Lugli, S., Manzi, V., Sierro, F.J., Bertini, A., Carnerlenghi, A., De Lange, G., Govers, R., Hilgen, F.J., Hubscher, C., Meijer, P.T., Stoica, M., 2014. The Messinian Salinity Crisis: Past and future of a great challenge for marine sciences. Mar. Geol., 352, 25–58. [Journal Article] Vasiliev, I., Karakitsios, V., Bouloubassi, I., Agiadi, K., Kontakiotis, G., Antonarakou, A., Triantaphyllou, M., Gogou, A., Kafousia, N., de Rafélis, M., Zarkogiannis, S., Kaczmar, F., Parinos, C., Pasadakis, N., 2019. Large sea surface temperature, salinity, and productivity-preservation changes preceding the onset of the Messinian Salinity Crisis in the eastern Mediterranean Sea. Paleoceanography and Paleoclimatology. 34. [Journal Article] Zachos, J., Pagani, M., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rhythms, and aberrations in global climate 65 Ma to present. Science, 292(5517), 686–693. [Journal Article]

ABSTRACT. 1. Introduction Gravitative sedimentation dominates deep basins in the Mediterranean and so far has received little attention in the Aegean Sea. An increase to sedimentation rates by a few orders of magnitude has been reported along the Hellenic Trench (Blanpied and Stanley, 1981; Anastasakis and Piper, 1991) and also in the South Aegean ( Koumoutsakou and Anastasakis, 1997;). Especially in the South Aegean volcaniclastic sedimentation can locally overprint any other sediment source (Anastasakis, 2006). However it is evident that there must be significant sediment source contributions from the recycled orogen.

2. Objectives The purpose of this study is to present and discuss univocal evidence on the different provenance of turbiditic sequences that were deposited in the deepest two basins of the South Aegean, the Karpathos Basin and the east Karpathos Basin, during the Upper Quaternary. A tight stratigraphic control, based on sapropel stratigraphy and tephrostratigraphy (Koumoutsakou and Anastasakis, 2017), provides a chronological framework in order to evaluate sediment parameters such as texture and provenance. 3. Methodology Two long Kullenberg piston cores, LC20 and LC23, were retrieved during Marion Dufresne Cruise 81 (MAST II PALAEOFLUX PROGRAMME EU-funded, 1995). The cores were scanned for magnetic susceptibility and then were sampled directly on board immediately after retrieval and splitting. Sediment Color was determined using the ‘Revised Standard Color Chart’ (1991). Samples were oven dried at 40 oC at the Department of Historic Geology-Paleontology.. Calcium carbonate content (%) was measured using the carbonate Bomb method (Muller and Gastner method,1971). Grain size analyses were performed by wet sieving for any sand fraction present and then using a Sedigraph 5100 with a MasterTech 051 auto sampler. Bulk mineralogy was determined by powder X-ray diffraction (XRD) (Siemens D8000, CuKa radiation, graphite monochro- mator, 35 kV and 35 mA, using a 0.02o step size and 1 s per step counting time), on randomly oriented samples ground with pestle and mortar. Minerals were estimated by measuring peak areas of main peaks on diffractrograms and peak heights after Muller and Mann method (1979). method (1979). Core No Location Latitude Longitude Water Depth Core Length LC-20 Karpathos Basin 35 40.05’N 26 52.10’E 2490m 23.70m LC-23 East Karpathos Basin 35 31.48’N 27 22.08’E 2154 19.33m

4. Results Four main sediment types were recognized in the two cores and were distinguished on the basis of magnetic susceptibility properties, colour, grain size and composition. Hemipelagic sediments, dark-coloured organic rich sapropel layers, tephra layers and turbidites that interrupt and distort all lithologies. Hemipelagic muds consist mostly of yellowish (10YR6/3) to brownish grey (10YR3/2 ) biogenic clayey marls and marly clays, with 25-65% CaCO3 and fine silt grain size. They are characterized by bioturbation and frequent foram /fossils tests. Mud turbidites are classified with enhanced direct grading as their main feature and their sandy fraction base. The sand fraction is mainly composed of quartz and calcite clasts and pelagic forams and pteropod fragments. (fig. 2). Many micro-turbidite layers have been identified in each core showing high sedimentation rates in both basins (Koumoutsakou & Anastasakis 1997). Dinstictive organic rich sapropel layers occur in both cores. They were classified based on the definitions by Kidd et al (1978) and found to be severely affected by reworking processes as described by Anastasakis and Stanley (1984). They are mostly well laminated with varied thicknesses turbidites developed over erosional bases and contain abundant pelagic and benthic foraminifera and pteropods. Tephra layers are characterized mostly by high susceptibility, can be reworked forming a volcaniclastic tourbiditic sequence. In between and within the above lithologies are developed mostly base cut out turbiditic units of Tde and rarely of Tbe and Tce Bouma sequence development. Median and modal diameters of tourbidites range from 500 μ to 1,1 μ. Bulk mineralogy of all lithologies has revealed that the most important provenance indicator is Dolomite. All turbidites with a medium sized sand to coarse silt base display Dolomite contents higher than 7% reaching as high as 30%. Core LC-20 retrieved in the deepest Karpathos Basin contains a higher proportion of coarse based, dolomite rich turbidites apparently originating from the west Karpathos and north Kasos shelf and flowing along the steep slopes. 5.Conclusions We clearly identify a high proportion of base cut out turbiditic sequences that display excellent textural sorting and fining upward grain size trends in both Karpathos and East Karpathos Basins. With the exception of a few volcaniclastic coarser turbidites all other coarser than medium silt turbitites contain significantly enhanced Dolomite contents , clearly denoting provenance of the sediments from the surrounding island shelfs. Sedimentation rates in the studied cores are at least one order of magnitude higher than the surrounding margins. Turbidites are more frequent during rapid first stages of transgressions.

6. References Anastasakis, G. C., & Stanley, D. J. (1984). Sapropels and organic-rich variants in the Mediterranean: sequence development and classification. Geological Society, London, Special Publications, 15(1), 497–510. Anastasakis, G., Piper, D.J.W., 2005. Late Neogene evolution of the western South Aegean volcanic arc: sedimentary imprint of volcanicity around Milos. Marine Geology 215, 135–158. Blanpied, Christian and Stanley, Daniel J. 1981. "Uniform Mud (Unifite) Deposition in the Hellenic Trench, Eastern Mediterranean." Smithsonian Contributions to the Marine Sciences. 13:1–40 Koumoutsakou O. and Anastasakis G., 1997. Lithostratigraphic framework of dynamic sedimentation in the SE Aegean Sea. 5th Symposium of Oceanography and Fishery, Athens, 1997. Koumoutsakou O., Anastasakis G., Smith V.C., Vougioukalakis G., Economou G. 2017 Tephrostratigraphic framework of sedimentation in the Karpathos basin, SE Aegean Sea. 5th RCMNS Conference “Exploring a “physical laboratory”: the Mediterranean Basin” 2017. Athens. Mann, U., Müller, G., 1979. X-ray mineralogy of Deep Sea Drilling Project Legs 51 through 53, western North Atlantic. Initial Rep. Deep Sea Drill. Proj. 51–53, 721–729. Müller, G., Gastner, M., 1971. The “Carbonate Bomb, a simple device for the determination of the carbonate content in sediments, soils, and other materials. N. Jb. Mineral., vol. 10, pp. 466–469.

ABSTRACT. Upper Cretaceous–Lower Eocene deposits of the Ionian basin are the major target in hydrocarbon exploration as they represent the reservoir rocks. These deposits mostly are composed of calciturbidites interbedded with breccia-microbreccia deposits. According to Bourli et al., 2019 the studied outcrops from Araxos area (internal Ionian sub-basin) showed that the breccia - microbreccia deposits are structureless, with a channelized geometry and calciturbiditic blocks internally to the channels; whereas most of the clasts were sourced from the underlying Lower Cretaceous “Vigla limestones”. Moreover, microfacies analysis indicate deep-water deposits and reworked shelf deposits. The intense extensional tectonic activity in the Ionian basin during the early Cretaceous, with synthetic and antithetic faults, produced active platform margins and asymmetrical grabens. During the late Cretaceous, the uplifted margins of the grabens caused erosion of the pre-existing deposits of the early Cretaceous “Vigla formation”. In order to have a better understanding of Upper Cretaceous-Lower Eocene evolution of the Ionian basin, two new-outcropped sections were selected around Amphilochia – Arta area (middle Ionian sub-basin). Amphilochia section is directed parallel to the thrust faults (NNW-SSE), whereas Arta section is directed parallel to the transfer or strike slip faults (NE-SW). In the new Ionian road, Amphilochia section, and although geological map showed the presence only of the Upper Cretaceous deposits, in the new sections the lower stratigraphic deposits correspond to the Lower Cretaceous Vigla shales or Vigla limestones, whereas Upper Cretaceous limestones rest unconformably over the Lower Cretaceous sediments. Lower Cretaceous deposits are characterized by strong discontinuity along the NNW direction, that mostly influenced by syn-sedimentary transfer faults. In addition, slumps were observed throughout the sections with E-W direction with a sliding from the east. These slumps are result of an instability probably produced from the N-S directed normal faults (Figure 1a). The dip direction of the beds is NNE-SSW. In the new Ionian road the Arta section, with a NNE-SSW direction, is strongly deformed due to many reverse faults, probably branches of the major thrust fault, situated west of the studied section. The above deformation is owed to the compressional regime (Eocene to Miocene) that influenced the whole area after the sedimentation. These deformations are recorded in many outcrops along the Ionian road and their general dip is 230o/50o (Figure 1b). Microfacies analysis carried out in thin sections from selected samples from Amphilochia, Arta and Kerasonas showed that most of the sediments deposits belong to deep marine environment (FZ 1 & 2), some of them showed a slope to shelf environment (FZ 3 & 4) and only a few showed shallow water environment. The main textural and compositional characteristics, as well as the sedimentary features of the distinguished microfacies are summarized in Table 1, corresponding to different depositional environments or facies zones (FZ: Flügel, 2010). More specifically, the “Vigla limestones” were classified as packstones/wackestones with scattered planktonic foraminifera and radiolarian limestones (standard microfacies SMF 3), indicating a deep-sea basin environment (FZ 1). Upper Cretaceous incudes pelagic wackestones with planktonic foraminifera (SMF3); microbreccia biolithoclastic packstones to grainstones (bioclasts, planktonic and benthic foraminifera (SMF4) indicating slope environment (FZ4) – toe of slope (FZ3), and, allochthonous bioclastic packstone to rudstone/floatstone breccia containing rudist and gastropod fragments, planktonic and benthic foraminifera, geopetal fractures (SMF5) indicating a slope environment (FZ4). Fenestral cavities and geopetal fractures in allochthonous material may indicate a source from a restricted or shallow shelf environment (FZ4) with the influence of meteoric water. The Paleocene pelagic grainstone containing planktonic and benthic foraminifera (SMF2), corresponding to a deep shelf environment (FZ 2) and finally, Eocene pelagic wackestones with planktonic foraminifera (SMF3), indicating a toe of slope environment (FZ3). In the Amphilochia new cross-section, with a N-S direction, the lower Cretaceous Vigla limestones and Vigla shales were outcropped for first time. This section is directed parallel to the paleo Ionian basin axis and the fact of the lateral discontinuity of Vigla limestones and Vigla shales indicate that during the sedimentation of these two formations there was a restriction along the paleo basin axis, probably due to synsedimentary transfer fault activity. In the Arta new cross-section, with a NE-SW direction, the upper Cretaceous Senonian deposits showed strong deformation that took place during the compressional regime that affected the Ionian basin after sedimentation. This deformation is stronger in the western part, close to a major thrust, and seems that this deformation could produce a high secondary porosity increase of upper Cretaceous deposits. The unconformably overlying Upper Cretaceous Senonian limestones are characterized by micro-breccia, calciturbidites and slumps, as recognized and in other areas (Bourli et al., 2019). Microfacies analysis showed in general a deep-sea environment with few exceptions with shallow environment character, introducing the existence of platforms, close to the studied sections.

ABSTRACT. Introduction The Aegean Region is characterized by a dense pattern of seismogenic faults, whose terminations at depths are not always well defined. Rheological modelling, by means of strength profiles calibration and realization, is used to determine the depth of the brittle-ductile transition (hereinafter BDT) within the broader area. In the present paper we focus on the Hellenides fold and thrust belt and Hellenic subduction zone comparing our results (in terms of BDT depth) with the depth of the recorded seismicity. The primary aim is to constrain some of the principal seismotectonic parameters for better defining the seismogenic potential of the active faults. Data and Methods We realized eight transects in the Aegean Region (see Fig. 1a). The first three start offshore Corfu (western Greece) and terminate around Thessaloniki (northeastern Greece) thus entirely crossing a continental collision setting. A second group of three transects is almost parallel but it has been traced across the active western Hellenic subduction zone of oceanic Nubian/Ionian lithosphere below the Aegean microplate; it initiates offshore of southwestern Peloponnesus and ends in the Attica region. Two more transects have been designed parallel to the axis of the Hellenides fold and thrust belt in order to cross and link the other two groups; one runs in a distal offshore position and the other mainly onland. The crosscutting geometry of the transects array allows to use the two intersections both as control points and as 3D-view insights on the thermo-rheological characteristics of the western Hellenides region. Each transect (except for the NNW-SSE trending ones, which are longer) has a total length of ~430 km and results from the projection of well-calibrated 1D strength profiles onto the transect direction (mean inter-space between the 1D profiles along a transect is ~10 km). By interpolating the closely-spaced strength profiles we obtained BDT depth, strength and temperature distributions at depth (here we limit the analysis to the first 100 km) for the eight transects. In order to realize the rheological transects we collected literature data for the values of the input parameters of the constitutive rheological equations from different studies, methods and sources. The literature data were then integrated with our geological and tectonic considerations in order to select the proper values and obtain reliable profiles. For the purposes of thermo-rheological modelling we used the simplified approach first proposed by Brace and Kohlstedt (1980) and then widely used in the literature (e.g. Ranalli and Murphy, 1987; Ranalli, 1995). Such a method consists in taking into account only the frictional sliding (brittle) deformation mechanism and the dislocation creep one, for respectively, the brittle and the ductile behavior. Results As regards the BDT depth, in the western 180-200 km the southern group of profiles (profile EE’, see Fig. 1c) displays a deeper transition than the northern one, with values comprised between 35 and 40 km. This is probably due to the (cold and old) oceanic nature of the crust in those sectors. After the 200 km mark, the sudden shallowing of the BDT to depths comprised between 15 and 10 km in the Oichalia and Kalamata regions is related to the upward shift of the rheological transition from the downgoing Ionian plate to the overriding Aegean plate. In the northern group of profiles (profile BB’, Fig. 1b) a similar trend of rapid shallowing of the BDT after ca 170-180 km is also observed. In this case however, the BDT is no ever deeper than 33 km even in the low surface heat-flow region at the western end (Corfu area). Such a behaviour is related to the continental nature of the crust within the undergoing plate and the associated intermediate/felsic typical lithologies (we selected quartzite and granulite for the upper and the lower crust, respectively) which tend to yield at lower shear stresses (and therefore minor pressures and depths) with respect to mafic lithotypes. After the 200 km mark the BDT shallows to depths comprised between 15 and 20 km, being therefore deeper than the corresponding sectors of the southern profiles. This could be explained by the lower surface heat-flow characterizing Epirus and northern Hellenides area with respect to Attica and northeastern Peloponnesus regions. From a rheological point of view the comparison between continental collision (BB’) and oceanic subduction (EE’) settings emphasizes the following differences and peculiarities: i) the occurrence of a deeper brittle layer just below the uppermost one in the continental settings, which is instead absent in the oceanic crust; ii) a thinner brittle layer in the back-arc region for the oceanic subduction setting; iii) the presence in the continental settings of brittlely deforming layers occurring in the intermediate and lower crust even below considerably thick ductile layers, especially when geothermal gradient and surface heat-flow are particularly low. Application to seismotectonics We used the depth of the BDT as a tool for constraining the geometrical (width and hence expected maximum magnitude) characteristics of some selected seismogenic sources taken from the GreDaSS database (Caputo et al., 2012). The selected sources crosscut either the transect BB’ or the EE’ and correspond to the South Kourveleshi Thrust (composite source, BB’), Paleochori Fault (individual source, BB’), Pamisos Fault (composite source, EE’) and the Fili Fault (individual source, EE’). The South Kourveleshi Thrust lies in the central-western sector of the BB’ transect, where on average the BDT is ~21-22 km deep; assuming a dip angle of 45° for this reverse fault and using empirical relationships a maximum expected magnitude of 7.1-7.2 is obtained which is consistent with the estimate of the GreDaSS database. The Paleochori Fault lies instead in the central-eastern portion of the BB’ transect. Here aftershocks of the 1995 Kozani-Grevena earthquake are distributed down to depths of ca 15-16 km (Rigo et al., 2004; Resor et al., 2005), being consistent with the BDT depth from our rheological modelling equal to ca 16 km. The maximum expected magnitude is in the order of 6.8, which is slightly higher than the value of Mw=6.5 of the 1995 earthquake. However, the estimate is considered to be acceptable, also considering that the 1995 earthquake did not produce surface ruptures and aftershocks did not occur any shallower than 4 km (Resor et al., 2005), indicating that probably the seismogenic rupture did not propagate for the entire thickness of the seismogenic layer (while our estimate are always conservative meaning that all the seismogenic thickness is ruptured coseismically). As regards the Pamisos Fault, this lies on the central sector of the EE’ transect; Also in this case the seismological data are in agreement with the BDT depth obtained from the rheological modelling, which is around 16 km. The calculated maximum expected magnitude corresponds to values around 6.8, which is consistent with the estimate given in the GreDaSS database equal to 6.7. The last selected source, corresponding to the Fili Fault is located close to the eastern termination of the EE’ transect. The BDT in this region is quite shallow, with depth of ca 9-10 km, consistent with the focal depth of the 1999 Athens earthquake being on average ~10-11 km and most of the aftershocks occurring above 11-12 km (e.g. Louvari and Kiratzi, 2001; Papadimitriou et al., 2002; Papadopoulos et al, 2004). We obtained a maximum expected magnitude of 6.3-6.4, which is slightly greater than the value of the 1999 mainshock. Also in this case however, it must be taken into account that the rupture only propagated upwards to depths as shallow as 3-5 km, and therefore the maximum magnitude associated to the Fili Fault could be greater and comparable to our estimate in the case of a rupture fully propagating throughout the entire seismogenic layer.

Figure 1. a) Terrain map of the Central-Eastern. Mediterranean Region showing the position of the investigated profiles; b) section of the difference between brittle (blue) and ductile (red) strength for the BB’ profile. The whitish colors indicate the brittle-ductile transition zones; c) same as b) but for the EE’ profile.

References Brace W.E., Kohlstedt D., 1980. Limits on lithospheric stress imposed by laboratory experiments. J. Geophys. Res. 85, 6248-6252. Caputo R., Chatzipetros A., Pavlides S., Sboras S., 2012. The Greek Database of Seismogenic Sources (GreDaSS): state-of-the-art for northern Greece. Ann. Geophys. 55(5), 859-894. Louvari, E., Kiratzi, A., 2001. Source parameters of the 7 September 1999 Athens (Greece) earthquake based on teleseismic data. Journal of the Balkan Geophysical Society 4(3), 51-60. Papadimitriou, P., Voulgaris, N., Kassaras, I., Kaviris, G., Delibasis, N., Makropoulos, K., 2002. The Mw= 6.0, 7 September 1999 Athens earthquake. Natural Hazards 27(1-2), 15-33. Papadopoulos, G. A., Matsumoto, H., Ganas, A., Karastathis, V., Pavlides, S., 2004. Deformation patterns associated with the M5.9 Athens (Greece) earthquake of 7 September 1999. Journal of Seismology 8(3), 381-394. Ranalli G., 1995. Rheology of the earth. 2nd ed. Chapman & Hall. Ranalli G., Murphy D.C., 1987. Rheological stratification of the lithosphere. Tectonophys. 132, 281-295. Resor P.G., Pollard D.D., Wright T.J., Beroza G.C., 2005. Integrating high-precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 Kozani-Grevena earthquake, Greece. J. Geophys. Res. 110, B09402. Rigo A., de Chabalier J.-B., Meyer B., Armijo R., 2004. The 1995 Kozani-Grevena (northern Greece) earthquake revisited: An improved faulting model from synthetic aperture radar interferometry. Geophys. J. Int. 157, 727-736.

ABSTRACT. Introduction Tectonic activity is a factor that affects the stability of fault-controlled escarpments in three ways (Brideau et al., 2005, 2009): (i) weakness zones develop along faults; (ii) it is associated with high relief and steep gradients and (iii) it can transfer can transfer inherited structures into the rocks to sites that are more susceptible to failures, e.g. they cause tilting of the fault-blocks by increasing the dips of the bedding. The relationship between active tectonics and landslide occurrence along marginal normal fault has been well established and described. However, the finding of such phenomena in older sedimentary sequences is more problematic. The occurrence of compressional structures within the Neogene and Quaternary deposits in the post-orogenic basins on the frontal part of the Hellenic arc has been observed and described in the last 4 decades (e.g. Meulenkamp et al., 1988; Alexopoulos 1990). Notwithstanding, their interpretation and the involvement of alpine rocks in these remains to be clarified. They have been described as structures of local importance, associated with faults that have significant horizontal displacement component (e..g. Fassoulas, 1999; ten Veen and Postma, 1999), or that they form part of syn-sedimentary landslide complexes (Meulenkamp et al., 1988). Recently, an older view, expressed by Mercier (1976) and re-emerged, in the sense that these structures are associated with large-scale compressional events that took place in the Upper Miocene- Pliocene, affecting the post-orogenic basins, in the form of out-of-sequence thrust faults (Tortorici et al., 2010). This paper focuses on a number of cases where compressional structures are observed within syn-tectonic deposits or, where alpine rocks are found to overlie Late Miocene – Pliocene sediment in basins of central Crete and the Northern Peloponnese. Tectonic setting The Peloponnese and Crete are the topographically higher frontal parts of the mountain chain that has been formed during the subuction of the African plate beneath the Eurasian one in Greece. Their evolution since the Upper Oligocene includes a series of tectonic episodes, through the formation of large compressional nappes, the exhumation of metamoprhics through extensional detachment faults and the formation of hanging-wall syn-tectonic basins; and ultimately the development of a complex network of high-angle brittle faults that bound the active tectonic basins (e.g. van Hinsbergen et al., 2006). Description and interpretation of the compressional structures A series of E-W trending, fault-controlled basins (terrestrial or marine ones) were formed in central Crete in the Upper Miocene. Sedimentation in these basins lasted until the Pliocene. One such example is the Spili basin, where Tortonian conglomerates are steeply tilted against the Spili boundary fault, at the foot of Mt Kedros. These conglomerates are overlain by Mesozoic carbonates of the Tripolis unit and the whole structure is covered by lateral scree and colluvial wedges. Such positioning of the Tripolis carbonates is attributed to landsliding that occurred at the late stages of rifting. The Apostolon-Amari basin (close to the Fourfouras village), located along the south-western flanks of Mt Psiloreitis, the geometry of the Tefelia and Vrysses formations is fault-controlled, and display N-NNE dips which become S-SSW close to the basin margin. The deposition in this basin took place on a highly faulted basement with intense palaeorelief and was controlled by a normal NW-SE fault that caused local dragging folds in the syn-rift sediemnts. Nowadays, along this fault zone, Late Pleistocene lateral scree has covered most of these structures. To the north, in the Rethymno basin and to the south of Perama, there are sediments of the Vrysses Group with slight northern slopes. Locally, small south-dipping reverse faults are also observed: these are related slumping events that occurred on the weakness planes defined by the bedding of the post-alpine deposits. Two more cases are examined, at Northern Peloponnese, along the southern margin of the Corinth rift. At the southern flanks of Mt Ziria (Kyllini) and north of Lake Stymfalia, a strip of Tripolis carbonates in sandwiched between steeply tilted (>30ο) synrift conglomerates. North of Mt Khelmos, east of Kalavrita, fluvial conglomerates are capped by Tripolis and Pindos carbonates, which in turn are covered by thick cohesive multimictic breccia, related to glacier erosion. Such positioning of the Mesozoic carbonates is attributed to landsliding that occurred at the early stages of rifting, during the deposition of the conglomerates. The ensuing flank uplift associated with the Corinth rift evolution cause the southward tilting of the early synrift deposits, while from the geomorphological viewpoint it led to the formation of the closed hydrological basin of Stymfalia. Conclusions The tectonic activity on the outer part of the Hellenic Arc since the Middle Miocene has led to the formation of basins bounded by normal faults. The continuing activity on these faults led to the formation of weakness zones, high relief, and the necessary depositional space. Locally –and where conditions were favorable- slides along the then marginal faults transported blocks of alpine rocks downhill, where they were finally emplaced atop the syn-tectonic sediments. The stratigraphic context of these slides (i.e. the age of the syn-tectonic sediments they are associated with), suggests that such activity took place during the late stages of basin evolution. The parallelism of the landslides with the margins of the basins highlights their close relationship, eventually rejecting the scenario for occurrence of a broad compressional event in the Upper Messinian- Lower Pliocene.

ABSTRACT. The south Aegean Sea and its adjacent areas is a highly segmented tectonically active domain, characterized by high-rate extension and severe crustal thinning. The different segments (blocks) that make up the south Aegean crust are bounded by significant fault zones and/or dislocation surfaces whose their relative motion varies in size and direction. The present study studies the kinematic characteristics of the southern Aegean crustal segments using geodetic data of 47 permanent GNNS stations distributed over the eastern Peloponnesus, Attica, Cyclades, Dodecanese, Crete and the coast of western Anatolia. Hitherto kinematic studies of the Aegean Plate have mainly focused on the regional strain field and large-scale relative motion between the Aegean, Anatolian and Eurasian plates, either using the ITRF coordinate frame or remote poles of rotation located in Western Europe or Africa. This approach does not facilitate discrimination of local-scale relative motion between tectonic blocks. Herein we are mainly interested in local-scale effects and base our analysis on a local reference point situated at Anavyssos, Attica. Given the reference point, westward of longitude 24E, the relative motion of tectonic blocks is somewhat uncertain as the majority of estimated relative velocities exhibits large errors, although least four well estimated vectors clearly indicate that the eastern Peloponnese slides in a roughly N210–N220 direction, expectedly and approximately normal to the strike of the western half of the Hellenic Trench. Eastward of longitude 24E errors are rather small and the distribution of velocities allows the identification of four major blocks with different kinematics, summarized as follows: 1) the Cyclades islands define a block that is moving in a SW (N210-N220) direction and is bounded by left-lateral dislocation surfaces of SW-NE orientation. 2) Crete is moving in a SE (N160) direction with an average velocity of 2.00 mm/yr. 3) The Dodecanese is moving in a SE (N120) direction with an average velocity of 7.35 mm/yr.; Crete and the Dodecanese appear to be ‘separated’ by unknown dislocation surface(s) of approximately N-S orientation located between east Crete and Karpathos/ Kasos islands. 4) The Cyclades and Crete-Dodecanese blocks appear to diverge at a variable rate that increases from east to west; the onset of the divergence coincides with the onset of severe crustal thinning in the Cretan Sea. In conclusion, the south Aegean appears to deform with a rather complex kinematic pattern, the origin of which remains to be confirmed and validated with future research.

ABSTRACT. Carbonate platforms have been a subject of research for more than twenty years. Much research work has focused on the effects that sea-level change, oceanographic factors and climate have on carbonate platform stratigraphic characteristics. In this contribution we aim to better understand the tectonostratigraphy of Carbonate platforms by showing examples from the eastern (Levant Basin) and the western Mediterranean (Offshore Greece; Papadimitriou et al., 2018). In particular, we propose that by comparing the evolution and the geometries of carbonate platform we can have a better of Carbonate platform basin systems. Four carbonate platforms (three Mesozoic and one Cenozoic) separated by main seismic surfaces have been identified on top of a basement high at the western margin of the Levant and western Greece (Figs. 1 and 2). The main seismic boundaries identified on top of carbonate platforms refer to erosional truncations, major flooding surfaces, downlap surfaces and slope onlap surfaces, whereas the seismic sequences in the deep basin are marked only by flooding and geometric unconformities (marine onlaps). The Tethyan Carbonate platform shows a lot of differences. For instance, to the east the Egyptian and the Levant platforms were invaded by terrigenous siliciclastics during the Jurassic- Cretaceous interval (Fig 3; Hawie et al., 2013; Tassy et al., 2015a). In contrast, the Eratosthenes and Apulia platforms located in a long distance from the continent were free from the continental influence (Fig. 3; Borgomano, 2000). Finally, the Mesozoic carbonate pile within the Cretan margin, is more likely associated to the Gavrovo-Tripolitza carbonate platform, which is well- known from studies in western Greece showing reservoirs in Early Jurassic and Cretaceous limestones. The seismic interpretation offshore Crete shows isolated carbonate buildups which appeared beneath the Messinian salt. The Tethyan carbonate platforms seem have been developed on basements highs. The position of basement-high is controlled by structures inherited from the Tethyan rifting (i.e., transform faults and a different crustal thickness between the Eratosthenes Seamount and the Levant Basin; Sagy et al., 2015; Granot 2016). Furthermore, the distance of the paleo-relief from the continent has a fundamental role in the evolution of a carbonate platform. For instance, these platforms have either been isolated (e.g., Apulia platform) or attached to the continent (Levant and Egyptian platforms).

Hence, this study can be used as a paradigm for further understanding of the predominant factors that control carbonate factories for other Carbonate platforms that can be found in the region.

References Borgomano, J., (2000). 'The Upper Cretaceous carbonates of the Gargano-Murge region, southern Italy: A model of platform-to-basin transition.' AAPG Bulletin, 84, pp. 1561-1588 Hawie, N., Gorini, C., Deschamps, R., Nader, F. H., Montadert, L., Granjeon, D. and Baudin, F. (2013) ‘Tectono-stratigraphic evolution of the northern Levant Basin (offshore Lebanon),’ Marine and Petroleum Geology. Elsevier Ltd, 48, pp. 392–410. doi: 10.1016/j.marpetgeo.2013.08.004. Papadimitriou, N, C. Gorini, F.H. Nader, R. Deschamps, V. Symeou, J.C. Lecomte, Tectono- stratigraphic evolution of the western margin of the Levant Basin (offshore Cyprus), Marine and Petroleum Geology, Volume 91, 2018, Pages 683-705, ISSN 0264-8172, https://doi.org/10.1016/j.marpetgeo.2018.02.006. Robertson, A. H. F. (1998) ‘Tectonic significance of the Eratosthenes Seamount: A continental fragment in the process of collision with a subduction zone in the eastern Mediterranean (Ocean Drilling Program Leg 160)’, Tectonophysics, 298(1–3), pp. 63–82. doi: 10.1016/S0040-1951(98)00178-4. Sagy, Y., Gvirtzman, Z., Reshef, M. and Makovsky, Y. (2015) The enigma of the Jonah high in the middle of the Levant basin and its significance to the history of rifting’, Tectonophysics. Elsevier B.V., 665, pp. 186–198. Santantonio, M., Scrocca, D. and Lipparini, L., 2013. The Ombrina-Rospo Plateau (Apulian Platform): Evolution of a Carbonate Platform and its Margins during the Jurassic and Cretaceous. Marine and Petroleum Geology,[online] 42, pp.4–29. Available at: . Tassy, A., Crouzy, E., Gorini, C., Rubino, J. L., Bouroullec, J. L. and Sapin, F. (2015a) ‘Egyptian Tethyan margin in the Mesozoic: Evolution of a mixed carbonate-siliciclastic shelf edge (from Western Desert to Sinai)’, MPG, pp, .565–581.

ABSTRACT. Abstract Although the geotectonic zones in western Greece are clearly thrusted on top of each other from east to west, in Crete these nappes are piled up cropping out thanks to tectonic windows. In western Greece, the Ionian islands provide a lot of information with regards to the most external parts of the Hellenides Thrust-and-Fold Belt (TFB). In addition, several wells and a dense seismic grid confirm the geological knowledge of the area and mitigate the uncertainty about the petroleum system there. In contrast, the area south of Crete includes only four (4) very small islands providing scattered information of the geological setting in the Cretan margin, along with a sparse seismic grid and the lack of wells. Despite more than forty (40) years of geological and geophysical work in the region, the geodynamic and tectonic processes have been debatable and controversial. An initial attempt to distinguish and outline the geotectonic zones present in the area south of the island of Crete has been done based on the integration of seismic data and onshore geology. However, because of the above-mentioned limitations the attempt remains speculative. The use of the seismic data allowed for a more accurate mapping of the three (3) distinct geological areas south of Crete; Cretan margin, Backstop and Mediterranean Ridge. The Cretan margin includes stacked nappes similar to those onshore Crete, the Backstop includes probably the most external Hellenides, while the Mediterranean Ridge cannot be assigned to any of the known Hellenides.

ABSTRACT. In this paper we integrate offshore and onshore data from the Katakolo area, NW Peloponnese, Greece, in order to examine the interaction of strike slip faulting and salt diapirism. Reprocessing of the legacy 3D seismic data in the offshore area show that the previously identified salt diapir is a narrow, elongated NNE-SSW to N-S trending salt wall that penetrates the Plio-Quaternary sedimentary rocks. The overburden adjacent to the salt structure is deformed by a series of NE-SW striking conjugate extensional faults. The later, close to the salt wall display a progressive ~20°-30° counter-clockwise rotation resulting in NNE-SSW strike which is consistent with a dextral shearing. Some faults show growth strata and listric geometry, while other are planar domino-style normal faults that root into deeper faults and the alpine rocks of the Ionian unit. In order to trace the northward continuation of the offshore faults we performed geological mapping in 1:5.000 scale at the Katakolo peninsula. We mapped two formations: i) The lower “Vounargos” formation and ii) the upper “Katakolo” formation. The contact between them is marked by an angular unconformity that can be nicely observed in the western part of the peninsula. The unconformity dips to the west-southwest and is submerged at the southern and southwestern part. The overall geometry of the Plio-Quaternary rocks shows that the whole peninsula is a fault block, tilted to the west-southwest and is bounded by a NNE-SSW trending fault at the southern part and an N-S trending fault at the eastern. Along these faults thermogenic gas seepages indicate connection with a deeper salt structure. Systematic fracture analysis on omnipresent extensional fracture sets from the Katakolo formation resulted in the calculation of the minimum horizontal stress that has a NW-SE strike, consistent with extension within a NNE-SSW trending dextral shear zone. From the geometry and the faulting pattern of the Plio-Quaternary sedimentary rocks in the offshore and onshore Katakolo, we conclude that the salt wall is supported by a deeper feeder and is formed along an active strike slip zone.

ABSTRACT. Subduction is key for driving for plate tectonics. Yet it is still unclear where and how subduction initiates in the oceanic domain. It is widely accepted that it critically depends on the rheology of the oceanic lithosphere (Nikolaeve et al., 2010) and can occur upon failure of the load-bearing crustal and mantle layers. When oceanic lithosphere is too strong, high shear strength of the oceanic lithosphere does not permit failure, and subduction may occur by deforming a passive margin at ocean-continent transition. However, weakening processes such as zones of serpentinized mantle may affect the strain localization (Maffione et al., 2015; Stern, 2004). Therefore, a series of experiments conducted to determine the favourable rheological and kinematic conditions that lead to the development of subduction zones in the intra-oceanic domain. These experiments involving both oceanic and continental domains which incorporate weak zones of realistic dimensions in the oceanic crust. Model results show that the key factor for the strain localisation is the difference in strength between the continental and oceanic upper crust. Analysis of deformation is used to define a boundary of rheological conditions enabling subduction in oceanic or in continental domain. Additionally, addition of a weak zones in a thick and strong oceanic lithosphere doesn’t affect the deformation pattern. However, presence of a weak zone in a relatively younger oceanic lithosphere (60 ± 10 My) may induce strain localization in the oceanic crust rather than at passive margin. This shows the importance of geological inheritance and thermo-mechanical feed-backs for the locus and evolution of subduction zone.

ABSTRACT. The Geohazard Supersites and Natural Laboratory initiative (GEO-GSNL) is a voluntary international partnership aiming to improve, through an Open Science approach, geophysical scientific research and geohazard assessment in support of Disaster Risk Reduction. This goal is pursued promoting broad international scientific collaboration and open access to a variety of space- and ground-based data, focusing on areas with high geohazard and risk levels. GEO-GSNL coordinates a global network of eleven geohazard Supersites, over which an international effort is carried out: space agencies provide satellite imagery at no cost for scientific use, monitoring agencies provide ground-based data, the international scientific community employs these data to generate new scientific results which are eventually delivered to national decision makers by the Supersite coordinators.

ABSTRACT. In this work the response of the build environment, after four strong earthquakes, is observed in Peloponnesus, Greece. Particularly the research is focused on monumental and other masonry buildings with load carrying masonry walls. This response is correlated with the recorded accelerations of the ITSAK accelerograph network. These records are postprocessed and numerical values of effective accelerations and of spectral accelerations are given for comparison reasons. The considered earthquakes are Kythera Eq., Koroni Eq., Leonidio Eq. and Achaia – Ilia Eq. At the location of each record, various levels of accelerations were recorded. These values vary from low to high. The response of the build environment was examined and recorded by visual inspections from ITSAK research groups, at the stricken areas. The buildings under research are subdivided in five categories. In the first category are classified buildings with mudbrick masonry walls and clay mortar. The second category contains buildings with stone masonry walls and clay mortar. In third category are classified buildings with stone and/or brick masonry walls and lime mortar. In the fourth category are classified the temple buildings and the surrounding structures. In the fifth category are classified castles, ancient ruins and other structures build with stone and masonry walls with or without mortar. For Kythera, Koroni and Leonidio Eqs were observed only cracks on masonry buildings while for Achaia-Ilia Eq were additionally observed total and partial collapses. It was found that in masonry buildings that are subjected to strong earthquakes first damages appear as cracks at the top floor. Probably this may attributed to the insufficient connection of the wooden roof with the walls. Also at the top storey the axial load of the piers are low and also the spandrels are not well wedged. The bell towers are usually constructed in contact with the building of the main temple. In these cases damages appear at the bell towers at the location of the top of the temple. This is justified by the consideration of the different way of oscillation of the two structural systems. Temple structural system is stiffer than the bell tower structural system. In many masonry buildings the distress and deformation of the walls are close to the failure values. This happen, mostly due to the absence of maintain in combination with antiquity. For these reasons after an earthquake usually appear cracks at the walls due to additional forces and deformations. From the field observations and by the use of the postprocessed earthquake records, resulted that the analysis seismic accelerations for monumental masonry buildings should be significantly lower than the recorded ones. In this work are given scientifically validated reasons for the reduction of analysis seismic loads by the reassessment of material properties and appropriate values are proposed. Also case studies are given, from the analysis of different monumental masonry buildings that are simulated by finite element models and the considered assumptions are approved.

ABSTRACT. Introduction Hydrocarbon seeps, mainly methane (CH4) of microbial and thermogenic origin, formed during sediment burial. Seabed fluid determines a wide range of fluids (gases and liquids) passing from seabed sediments to seawater. The significance of seabed fluid flow goes beyond the geosciences, since they have a major impact to marine ecology and chemistry, representing also an important greenhouse gas source for the atmosphere (e.g., Etiope, 2004; Papatheodorou et al., 2007; Etiope and Ciccioli, 2009). Moreover gas seeps could be a geo-hazard for the social community, the constructions and the industry. The link between gas emission and seismicity has been the subject of a wide number of multidisciplinary studies. Mellors et al. (2007) found significant statistical correlations between large earthquakes (M > 5.5) and the eruption of mud volcanoes. Signals recorded by Ocean Bottom Seismometers (OBSs) were explained as due to bubbles coming from gas seepage at the seafloor (Tary et al., 2012). Embriaco et al. (2013), suggested a link between seismic energy release and methane seepage using data from a multiparametric benthic observatory along the North Anatolian Fault in the Sea of Marmara. Two major harbour in Western Greece, have been established over active, intense gas seepage areas, Patras Harbour (Christodoulou et al., 2003) and Katakolo Harbour (Etiope et al., 2006). Laboratory of Marine Geology & Physical Oceanography, participating among others, in three EU projects, has been used underwater benthic observatories for seepages activity monitoring. Geological Setting In Patras Gulf, a pockmark field has been developed in soft, layered Holocene silts, showing episodes of gas venting from the Pleistocene/Holocene interface which forms a gas accumulative horizon (Christodoulou et al., 2003; Papatheodorou et al. 1993). It is one of the most well documented pockmark field regarding its activity and the relationship with seismicity. On July 14th, 1993 an earthquake of magnitude M=5.4 on Richter scale was recorded in the active Patras graben. In a temperature recording station in the pockmark field, the temperature increased anomalously on three occasions prior to the earthquake and the earthquake occurred just after the last peak of increased temperature. Furthermore, it was noted that some pockmarks few days after the earthquake were still venting gas bubbles as is indicated by the extremely high reflectivity plumes shown on the sonographs (Hasiotis et al., 1996). On June 2008, after a major earthquake of ΜW=6.4R, which occurred on the Northwestern Peloponnese and for a period of fifteen days, gas plumes were recorded in the water column above pockmarks and methane measurements showed high concentrations of dissolved methane in the water column all over the pockmark field (Christodoulou et al., 2009). Katakolo is one of the most productive thermogenic gas seepage zones in Europe and the biggest methane seep ever reported in Greece. The gas seepage takes place over an extended area in the Katakolo harbour and along two main normal faults off the harbor. Based on side scan sonar sonorgraphs at least 823 gas bubble (10-20 cm in diameter) plumes escaping over an area of 94,200 m2 were recorded, at depths ranging from 5.5 to 16 m. The gas consists mainly of methane and has H2S levels of hundreds to thousands ppmv, and shows significant amounts of other light hydrocarbons like ethane, propane, iso-butane and C6 alkanes. Due to the shallow depth, more than 90 % of CH4 released at the seabed enters the atmosphere and the gas seeps may produce severe geohazards for people, buildings and construction facilities due to the explosive and toxicological properties of methane and hydrogen sulfide, respectively (Etiope et al., 2005; 2006; 2013; Christodoulou, 2010). Methodology and Results In Patras Gulf gas monitoring module (GMM) has been developed for continuous and long-term measurements of seabed gas seepage integrated with seawater physical parameters data. GMM equipped by three semiconductor methane sensors, an H2S electrode microsensor and a CTD SBE-37-SI Microcat (Sea Bird) for measurements of temperature, conductivity (C), temperature (T), and depth (D, or pressure, P) sampled every 10 minutes (Marinaro et al., 2006). GMM was deployed at the base of a large pockmark, at a water depth of 42 m. Recordings were carried out in two consecutive campaigns over a period of about 6.5 months. This was the first long-term monitoring ever done on gas leakage from pockmarks by means of CH4+H2S+T+P sensors. The results showed frequent T and P drops associated with gas peaks, more than 60 events in 6.5 months, likely due to intermittent, like pulsation, seepage. Decreases in temperature below an ambient T, were associated with short-lived pulses (10-60 min) of increased CH4+H2S concentrations. This seepage “pulsation” can either be an active process driven by pressure build-up in the pockmark sediments, or a passive fluid release due to hydrostatic pressure drops induced by atmospheric wind. A newer version of GMM, equipped among others sensors, with a current meter, deployed at the eastern part of the Katakolo harbor at water depth of -7m, where intense gas seepage and oxygen concentration reductions have been identified during preparatory surveys. GMM monitoring lasted 3.4 months (101 days). From detailed observation of the GMM parameters (CH4, O2, temperature, turbidity, current speed and direction) and wind speed obtained from the local meteorological station, 8 main periods were observed when dissolved oxygen concentration decreases and reaches hypoxic up to quasi-anoxic levels. Within these 8 periods, 54 short term (scale of hours) hypoxia events and 43 short term CH4 peaks were observed, which in more than 95% of cases were followed by O2 decrease. Current speed in combination to elevated CH4 concentrations appeared to be the key factor responsible for the hypoxia and quasi-hypoxia events. When current speed is relatively steady and low (<4 cm/s) for a considerable amount of time (>4 h) and at the same time CH4 concentration rises, dissolved oxygen concentration lingers at hypoxic levels and may even reach quasi-anoxic levels. The longest event of continuous hypoxia was almost 2 days, which was coupled with low current speed and elevated CH4 concentrations. At the same place a prototype fiber-optics-based monitoring system implemented both a distributed temperature sensor (DTS) and an intelligent distributed acoustic sensor (iDAS) of Silixa, Ltd. As far as we know, this was the first time that DTS and iDAS were used in marine environment. The iDAS system makes it possible to observe the acoustical signal along the entire length of an unmodified optical cable, detecting bubble plumes and allowing seepage detection and quantification. The DTS system can measure temporal variations of the gas plumes. A large metal pyramid frame was constructed, where fiber optic cable wrapped, and deployed on the seabed. The preliminary analysis and interpretation of the collected data showed that the lower temperature values indicate gas leakage points. The cooler monitoring points are, at the same time, the points with the smallest typical daytime temperature deviations. Furthermore, a certain spatial pattern and a systematicity has been observed regarding the location of the colder monitoring points. This indicates possible permanent leakage points. iDAS data (acoustic footprint of the bubbles upon escape) is in agreement with the spatial temperature distribution of the DTS. Confirmation of these possible gas escapes also results from submarine optical reception of the fiber-optics-based monitoring system. Small local earthquakes of 1.3 to 2.8R, during the experiment, do not appear to affect the leaks. Acknowledgements The surveys presented in this chapter were carried out within the framework of three European Union funded projects (ASSEM, contr. EVK3-CT2001-00051, PYTHAGORAS II. Social Funds, HYPOX project EC Grant 226126, ENV.2008.4.1.2.1, FP7). References Christodoulou, D., 2010. Geophysical, geotechnical, sedimentological and remote sensing monitoring of active pockmark fields in high seismicity region, Western Greece. PhD Thesis, University of Patras. 296p. Christodoulou, D., Papatheodorou, G., Fakiris, E., Etiope, G., Ferentinos, G., 2009. The activation of the Patras gulf pockmark field triggered by the June 8, 2008 earthquake. In Proceedings of 9th Panhellenic Symposium of Oceanography and Fisheries, p. 3-8. Christodoulou, D., Papatheodorou, G., Ferentinos, G., Masson, M., 2003. Active seepage in two contrasting pockmark fields in Patras and Corinth Gulfs, Greece. Geo-Marine Letters 23,194-199. Embriaco, D., Marinaro, G., Frugoni, F., Monna, S., Etiope, G., Gasperini, L., Polonia, A., Del Bianco, F., Namik Çaǧatay, M., Ulgen, U.B., Favali, P., 2013. Monitoring of gas and seismic energy release by multiparametric benthic observatory along the North Anatolian Fault in the Sea of Marmara (NW Turkey). Geophysical Journal International, 196 (2), pp. 850-866. Etiope, G., Christodoulou, D., Kordella, S., Marinaro, G., Papatheodorou, G., 2013. Offshore and onshore seepage of thermogenic gas at Katakolo Bay (Western Greece). Chemical Geology 339, 115-126. Etiope, G., Ciccioli, P., 2009. Earth’s degassing – A missing ethane and propane source. Science, 323, 5913, 478. Etiope, G., 2004. GEM – Geologic Emissions of Methane, the missing source in the atmospheric methane budget. Atmospheric Environment, 38, 19, 3099-3100. Etiope, G., Papatheodorou, G., Christodoulou, D., Favali, P., Ferentinos, G., 2005. Gas Hazard Induced by Methane and Hydrogen Sulfide Seepage in the NW Peloponnesus Petroliferous Basin (Greece). Terrestial, Atmospheric and Oceanic Sciences 16, 897-908. Etiope, G., Papatheodorou, G., Christodoulou, D., Ferentinos, G., Sokos, E., Favali, P., 2006. Methane and hydrogen sulfide seepage in the NW Peloponnesus petroliferous basin (Greece): origin and geohazard. AAPG Bulletin. 90, 701-713. Hasiotis, T., Papatheodorou, G., Kastanos, N. Ferentinos, G., 1996. A pock-mark field in the Patras Gulf (Greece) and its activation during the 14/7/1993 seismic event. Marine Geology 130,333-344. Marinaro, G., Etiope, G., Lo Bue, N., Favali, P., Papatheodorou, G., Christodoulou, D., Furlan, F., Gasparoni, F., Ferentinos, G., Masson, M., Rolin, J-F., 2006. Monitoring of a methane-seeping pockmark by cabled benthic observatory (Patras Gulf, Greece). Geo-Marine letters 26, 297-302. Mellors, R., Kilb, D., Aliyev, A., Gasanov, A. & Yetirmishli, G., 2007. Correlations between earthquakes and large mud volcano eruptions, Journal of Geophysical Research, 112, B04304. Papatheodorou, G., Hasiotis, T., Ferentinos, G., 1993. Gas charged sediments in the Aegean and Ionian Seas, Greece. Marine Geology 112, 171-184. Papatheodorou G., Christodoulou D., Geraga M., Etiope G., Ferentinos G (2007) “The pockmark field of the Gulf of Patras: An ideal natural laboratory for studying seabed fluid flow” In: ZELILIDIS, A., PAPATHEODOROU, G. and GERAGA, M. (eds.): Sedimentology of western and central Greece from recent to Triassic. 25th IAS Meeting of Sedimentology, Patras, 2007, Field Trip Guidebook, p. 43-62. Tary, J.B., Geli, L., Guennou, C., Henry, P., Sultan, N., Cagatay, M.N. & Vidal, V., 2012. Micro-events produced by gas migration and expulsion at the seabed: a study based on sea bottom recordings from the Sea of Marmara, Geophysical Journal International, 190, 993–1007.

ABSTRACT. This study aims to highlight the potential of structural stability risk assessment for the areas of Nafplio and Lavrion part of the EnCeladus hellenIc Supersite under the terms of the research project STructural stABiLity risk assEssment (STABLE). The project will introduce a strategy and select most efficient methods and tools for harmonization of data, criteria and indicators to be addressed for tracking of impact of environmental changes on tangible cultural heritage (CH) assets, buildings and monuments, including structural deterioration processes at a city/village scale. The material and structural properties of heritage buildings, with special attention to foundation conditions, will be the focus of interest in order to assess their behaviour when exposed to ground motions. These valuable information need to be complemented, calibrated and tested with ground data (e.g. geotechnical information), site scale monitoring (e.g. ground monitoring stations, laser scanners etc.) and risk forecasting models (earthquake) to derive end-user driven products (e.g. hazard, vulnerability and risk maps). The target customers of the project are the public bodies in charge to preserve the CH, Urban Planners, Academic Communities and private enterprises active in the specific sector. The project addresses the design and development of an IT service platform, combining advanced satellite technologies with existing ground-based data and risk forecasting modelling for the long term and continue monitoring and update of structural stability of the architectural heritage and in particular of historical centers affected by geo-hazards. The platform will provide alert models (geotechnical/structural risk forecasting models) based on a fixed infrastructure where technical parameters, gathered in the GIS environment (EO products, ground-based data, documentation etc.), are implemented for each test site. The platform will offer information in support to prevention of damage at CH in the form of regularly updated maps of element at risk, allowing to follow and predict the evolution of a risk, and consequently being able to give information usable for a priori actions before damages or disaster can occur. This information will enable the authorities responsible for the preservation of CH sites to carry out an effective planning and implementation policy of preventive maintenance and drastically improve the resilience factor of the CH asset. STABLE aims to bring together the excellence of Research Centers and SMEs with interdisciplinary skills built around CH but ranging from Civil and Geo-technical engineering, to Information Technology and remote sensing. The project implements knowledge exchange and interdisciplinary actions, to go forward in research towards novel techniques and improved monitoring and managing tools specifically developed for CH. More specifically, the objectives of STABLE are the following: • Obj-1: Collection of data from different monitoring techniques, such as satellite, terrestrial and autonomous airborne inspection systems as well as ground techniques, to perform the monitoring of CH sites and related surrounding areas, thus integrating novel remote sensing technologies. • Obj-2: Definition of risk modelling systems enabling the forecast of structural stability of CH in different scenarios of seismic movements. More specifically, the objective will focus on the use of novel models taking advantage of data derived from satellite and ground-based techniques, for the definition of ad-hoc risk models of the structural stability of the CH and its resilience to different earthquakes scenarios. • Obj-3: Development of a web-GIS tool for risk analysis of structural stability of CH integrating risk forecasting models with ground and remote sensing datasets. Demonstration activities will be carried out in the selected test cases in order to validate the approach. • Obj-4: Address the importance of new technologies for sites monitoring and management with specific focus on the viability and sustainability of future commercial services based on the technologies improved, developed and verified in Obj-1 to Obj-3. • Obj-5: Push innovation through the development of an initial research and training network that will focus its activities on the development, effective integration and increased utilization of existing and innovative technologies in the field of structural stability of CH. • Obj-6: Provide researchers and professionals with the opportunity to go beyond the current state-of-the-art in the specific field, through a multidisciplinary and international approach based on a wide spectrum of technological tools and methods that can contribute to a more effective CH preservation and conservation. • Obj-7: Build up specific complementary and market oriented skills to allow the European researchers and professionals to face the new challenge in terms of technology development and future services and improve their ability to face new opportunities in the emerging markets. In order to carry out the demonstration and validation of the platform, 2 Greek case studies have been selected: i) the old city center of Nafplio and ii) the ancient Lavrion. Both are located in the area of the EnCeladus hellenIc Supersite.

Acknowledgements This work was prepared in the framework of the STructural stABiLity risk assEssment project (STABLE), H2020-MSCA-RISE-2018 with Grant Agreement number: 823966.

ABSTRACT. Characterizing active faults and quantifying their activity are major concerns in Greece. Geodetic measurements including GPS and leveling have provided valuable observations of crustal deformation. The GPS network, with stations generally spaced less than 10 km apart, could highlight mainly regional and in some cases local displacements. However, these measurements do not provide the high spatial resolution needed to detect in detail surface creep on individual faults. Monitoring of active faults in areas of high exposure both building store and population is of great importance, providing useful information to assess seismic hazards and risks. Our study area is located in the Beotian geographic department of Greece (Kaparelli – Plataies area) and ends up in the eastern Gulf of Corinth (Kalamaki bay). Surface topography and geomorphology of the Corinth Gulf are clearly associated with seismic activity along large normal faults. The 1981 earthquake sequence, which was characterized by shallow earthquakes (<10km) and magnitudes greater than 6 (Abercrombie et al., 1995), and especially the third shock, ruptured the Kaparelli fault which was activated during that period and produced extensive ground deformation. The fault is characterized as a complex fault zone due to its numerous fault segments. It is a south dipping normal fault with an active fault plane dipping at about 45o. This fault is a segment of a greater normal fault zone that is situated to the north of Parnitha Mountain in Central Greece. Recent geological data (Drakatos et al., 2005) showed that the Kaparelli area forms the boundary between fast-slipping normal faults in Corinth-Perachora regions and slow-slipping faults in Viotia, Attica. Spaceborne Synthetic Aperture Radar (SAR) interferometry is a technique that produces 3D topographic data of Earth’s surface directly from two SAR images (Bamler and Hartl, 1998). An extension of the basic technique, called differential SAR interferometry (DInSAR), allows measurements of land deformation and it has various applications in the fields of volcanology, cartography, crustal dynamics, slope instabilities and land subsidence. Using large stacks of SAR images acquired over the same area, long deformation time series can be analyzed using multi-temporal differential SAR interferometry techniques like Permanent Scatterers Interferometry (PSI) (Ferretti et al., 2001), Small Baseline Subset (SBAS) (Berardino et al., 2002), Interferometric Point Target Analysis (IPTA) (Werner et al., 2003), Stanford Method for Persistent Scatterers (StaMPS) (Hooper et al., 2004), Coherent Pixel technique (CPT) (Blanco-Sanchez et al., 2008). Multi-temporal DInSAR is nowadays a well-documented technique for the characterization of ground motions over large spatial areas and is capable of detecting movements with metric resolution and millimetric accuracy. The area of interest is a part of the Corinthian Gulf characterized by active tectonism and seismic activity. The main purpose of this paper is to detect potential displacement along the Kaparelli fault and its strands by the synergy of MTInSAR and geological field observations. Concerning MTInSAR a rich dataset of 92 ascending and 55 descending SLC Sentinel 1 A & B scenes covering the period October 2014 to November 2018 were processed using the SARPROZ s/w following the Persistent Scatterers Interferometry technique (PSI). Field observations include a fault scarp height model (based on field data) and a map of the main ruptures’ traces (based on field measurements, using Field Move Clino app). Combining interferometric results and geological field work can lead to a better understanding of a fault’s movement and the ground deformation that it causes and thus contribute to seismic hazard assessment. Although monitoring concerns a short period few patterns of low rate of deformation are detected and an attempt to associate them with the local tectonism.

ABSTRACT. With increasing growth of the urban environment as population migration dominates land use, the resilience of urban ecosystem services is under critical pressure. Urban soils provide many significant functions for wider urban management and identifying their role as a source or sink of urban pollution is critical if we are to resolve their contribution to remediating and sustaining healthy urban ecosystems. A series of projects linked to defining the state and function of urban soils in a number of European cities provides opportunities to study source terms and baseline conditions for typical metallic (potentially toxic elements – PTEs) and organic pollutants (e.g. PAHs, PCBs). These studies highlight high levels of variability due to the wide range of inputs and the sources of contamination from air pollution through to direct introduction of wastes and the effects of urban management practice. Work includes the derivation of sources from the multivariate analysis of data on soil pollution from metallic elements, soil properties and basic indicators. The tools developed to assess impacts on desired soil function e.g. in supporting urban green infrastructure such as forestry, agriculture and recreational space and must form part of the management strategy to ensure reliable clean up and maintenance of urban ecosystems.

ABSTRACT. The environmental impact of urban development is a major concern of our times and the management of contaminated urban areas is a significant societal challenge at global scale with legal, financial and possible human health implications as over 50% of the global population resides in cities. Potentially harmful elements (PHEs) including trace metals and metalloids are always high in the agenda of urban environmental studies because of: a) their multiple industrial, domestic, medical and technological applications that have led to their wide distribution in urban environments, and b) their non-degradable character. An increasing body of scientific evidence suggests that measuring the total concentration of PHEs in soil and other environmental compartments in big cities does not provide an effective basis for the evaluation of potential adverse effects to humans and the environment and tends to overestimate the risks and induce unnecessary remediation costs (Cipullo et al. 2018 and references therein). Rather, the elemental mobility and bioaccessibility of the contaminants have central role in understanding human exposure, as the chemical structure of PHEs and associated mineral phases affect their solubility in physiologic fluids and influence the absorption capacity of the human body. Risk-based environmental management decisions can also be impaired due to the fact that exposure to contaminant mixtures is often overlooked and receptor population vulnerabilities that can be profound in big cities are not taken into account. Here, we present results from a series of studies concerning the urban environment of Athens Greece with the aim to demonstrate how geochemical mapping at different spatial scales, combined with chemical methods and mineralogy can provide insights for better interpretation of PHEs environmental mobility. The ultimate aim is to contribute to improved planning and management of the urban development of Athens, the capital city of Greece with a population of over 3 million people. Initially, a geochemical baseline study of surface soil, based on a systematic sampling survey covering the Greater Athens and Piraeus area, was implemented (Argyraki and Kelepertzis, 2014). The near total concentrations of the major elements Fe, Al, K and Ca, and PHEs Ni, Cr, Co, Mn, As, Pb, Zn, Cu, Cd, Sb and Sn were determined. Principle Component Analysis and Cluster Analysis, combined with analysis of soil heterogeneity and spatial variability, were implemented in order to distinguish the sources of elements and their classification as geogenic or anthropogenic. The geochemical maps showing the overall spatial distribution patterns of elemental concentrations were plotted using a GIS and the Inverse Distance Weighted (IDW) interpolation method with a power of 2. Geographically Weighted Regression was used to evaluate the spatial correlations between the studied elements. It was found that the major factor controlling variability of the chemical composition of surface soil is the bedrock chemistry, resulting in a significant enrichment in concentrations of Ni, Cr, Co and possibly As. Anthropogenic influences are also significant, controlling elements that are typical of human activities, i.e. Pb, Zn, Cu, Cd, Sb, and Sn. The highest concentrations of the classical urban contaminants are observed in the surface soil from roadside verges and in the older parts of the city, as well as the densely populated areas. Spatial distribution patterns of PHEs demonstrated an increase in concentrations of the anthropogenic PHEs towards the city core (Figure 1). The aqua regia extracted (pseudototal), potentially phytoavailable, mobilizable, orally bioaccessible and reactive pools of PHEs were subsequently operationally defined by applying adequate chemical reagents on 45 urban top-soil samples (Kelepertzis and Argyraki, 2015). Despite the elevated pseudototal concentrations of geogenic elements (Ni, Cr, As and Co) in Athens soil, their availability is limited because of their sequestration in stable mineral phases. The pseudototal content of the anthropogenic group of elements (Pb, Zn, Cu, Cd) is the predominant factor controlling their availability. An association between available fractions of this group of elements and amorphous Fe oxides has been observed based on detailed mineralogical analysis of soil grains by Scanning Electron Microscopy- Energy Dispersive Spectroscopy (SEM-EDS) (Figure 2). The study of Pb isotopic ratios in selected soil and house dust samples indicated that Pb in Athens soils is a mixture of local soil background Pb with high 206Pb/207Pb ratios and Pb derived from the re-suspension of particulates deposited from past vehicular exhaust emissions of leaded gasoline with a low 206Pb/207Pb ratio (Kelepertzis et al., 2016). The house dusts exhibit anthropogenic enrichment of vehicular traffic-related Pb, Zn and Cu in relation to the urban soil. Furthermore, anthropogenic PHEs in house dust were found to be associated with the magnetic fraction that is enriched in magnetite (Kelepertzis et al., 2019). Examination of selected spherules (size > 30 μm) by electron back scatter diffraction (EBSD) in a Field Emission SEM instrument produced pattern image quality maps that helped to verify the magnetite crystal phases, while the focused ion beam (FIB) technique confirmed the high-temperature industrial origin of the magnetite spheres (Figure 3). Such spherical particles have also been identified in the exterior soil indicating that they are ubiquitous in the urban chemical environment of Athens. The similarity in the Pb isotope results and the microstructure of particles between the urban soil and the house dust material suggests that these two environmental sampling media share common industrial and traffic-related sources. We conclude that combining data of geochemical mapping from micro- to macro-scale with chemical data and detailed mineralogical observations can provide invaluable information for further studies of exposure assessment and environmental management in urban areas.

ABSTRACT. Urban deposits (road dusts and gully sediments) are reflective of a wide range of anthropogenic activities, and are a useful resource for evaluating the level and distribution of trace metal contaminants in the surface environment. Τhe drainage system of the cities might play an important role in terms of capturing or releasing trace metal contaminants to the receiving aquatic bodies (Duzgoren-Aydin et al., 2014). Monitoring of the urban environment of Greece’s capital, Athens, provides important information about how trace metal concentrations behave within the seasons and how they contribute to the urban pollution. Chemical partitioning of the contaminants in both road dusts and gully sediments can therefore be useful to evaluate the long-term fate of the contaminants in the urban system. Urban sediment samples have been collected and analyzed in different altitudes within the Athens basin based on the hydrographic network of the area. A total of 26 urban sediments and soil samples were collected and analyzed for 33 elements following aqua regia dissolution. The soil organic carbon content, soil pH and grain size distribution have been determined and magnetic susceptibility measurements and mineralogical analysis by powder X-ray diffraction were also performed in order to identify possible factors explaining the variability of elemental concentrations. The BCR sequential extraction protocol was subsequently applied to a set of ten selected samples with the highest concentrations of trace metals (Cd, Co, Cr, Cu, Ni, Pb, Zn). Seasonal sampling of the selected sampling sites over one year was also performed followed by analysis after a 0.43 M HNO3 extraction. Aqua regia concentrations in analyzed sediments reached maximum values of 18mg/kg for As, 2mg/kg for Cd, 14mg/kg Co, 193mg/kg Cr, 640mg/kg Cu, 25600mg/kg Fe, 112mg/kg Ni, 3092mg/kg Pb and 1469mg/kg Zn. The median values of the studied elements were estimated to be 13mg/kg for As, 1mg/kg for Cd, 8mg/kg Co, 98mg/kg Cr, 215mg/kg Cu, 17154mg/kg Fe, 70mg/kg Ni, 267mg/kg Pb and 598mg/kg Zn respectively. With the exception of Co and As, both maximum and average values were found to be much higher than those presented for Athens soils in a previous study (Kelepertzis et al., 2015). Cluster analysis on the results identified two major groups of elements based on a > 43.59% criterion of similarity. The first cluster contains elements of geogenic origin including Co, Fe, Mn and Ni. The parameters of % soil organic carbon, magnetic susceptibility, Cu and Cr are grouped together in a second cluster showing similarity level > 65% while a third cluster groups together Pb, Zn and Cd and is interpreted as anthropogenic. Sequential extraction results correspond to this grouping as the anthropogenic elements tend to be released in the first two extraction steps. Cadmium and Zn are the only metals showing significant association with the exchangeable fraction, reaching 40%, suggesting that they are the most susceptible metals to mobilization during runoff. Moreover, Cu and Pb are largely associated with the oxidisable fraction. Metal fractions identified as showing larger associations with the reducible and oxidisable fractions will continue to be vulnerable to mobilization as a result of changes in ambient pH and/or redox conditions (Robertson et al., 2002). No significant seasonal variation has been observed for all the studied elements except Cd which displayed significantly lower concentrations during the December sampling period. Due to the close proximity to human population, soils and dust in cities and towns that are contaminated by trace metals, either of natural or anthropogenic origin, represent a potential risk for the residents through several pathways (Kelepertzis et al., 2013). Urban surface drainage deposits are the main sinks where dust, urban soil and anthropogenic sediments can be trapped. Briefly, it was documented that the type and extent of contamination in the surface environment of the Athens basin reflects the characteristics of the anthropogenic activities taking place, and that traffic- related activities are the primary sources of contaminants in the city.

ABSTRACT. High nitrate (NO3-) concentrations in groundwater occur in many areas around the world, largely as a result of excessive application of fertilizers, animal manure and inappropriate sewage management. A series of recent publications have established that naturally-occurring Cr(VI) is prevalent in groundwater associated with ultramafic aquifers in Greece (for example Kaprara et al., 2015). There is some evidence that increased NO3- in alluvial aquifers of agricultural areas may exacerbate the mobilization of Cr(VI) via intensive groundwater recharge through the vadose zone and associated increased contact with Cr-containing minerals or nitrification of ammonium in fertilizers (Mills et al. 2011). Coupled nitrogen and oxygen isotopes of NO3- have proven useful in providing detailed information regarding the NO3- sources and transformations in groundwater systems. Here, we applied the combined use of the δ15Ν and δ18Ο in NO3- from groundwater systems in Greece, previously identified to contain elevated Cr(VI) concentrations (for example Pyrgaki et al 2016), with the aim to determine the NO3- sources and examine the possible linkage of N cycling to Cr(VI) mobilization. The porous aquifers from Schinos, Central Evia and Thiva regions have served as prime examples where both anthropogenic NO3- contamination and ultramafic-derived Cr(VI) affect the groundwater chemistry. A total of 28 groundwater samples from productive wells and bores were collected from the three study areas during November 2017 (dry period): 9 samples from Schinos (borehole depth ranging from 4 to 55 m), 13 samples from Evia (depth ranging from 4 to 250 m) and 6 samples from Thiva (depth ranging from 150 to 250 m). Concentrations of dissolved NO3- and Cr(VI) were determined after well-established international protocols for water sampling, handling, preservation and analysis. The δ15Ν and δ18Ο of NO3- were analyzed using the bacterial denitrification method. Hexavalent Cr concentrations for this specific data set ranged from 10 to 112 μg/L in Thiva, 12 to 121 μg/L in Schinos and 11 to 189 μg/L in Evia. Nitrate concentrations showed a different distribution, with the highest concentrations determined in Evia (median 120 mg/L, range from 18 to 334 mg/L), followed by those in Thiva (median 66 mg/L, range from 21 to 151 mg/L) and Schinos (median 46 mg/l, range from 9 to 70 mg/L). The isotopic composition of NO3- for the whole data set ranged from 2.4 ‰ to 21 ‰ for δ15N, and from -0.73 ‰ to 15.3 ‰ for δ18Ο. Potential sources of NO3- in the studied aquifers include the application of synthetic fertilizers and manure in the agricultural fields of Evia and Thiva regions, and the existence of residential waste cesspools in Schinos and Evia areas. The NO3- isotope ratios in most studied water samples fall in the compositional range of NH4+ in fertilizer, soil N and manure/septic waste (Fig. 1). The soil N cannot be considered to be the main origin of NO3- because NO3- concentrations were much higher than expected concentrations produced by the mineralization of soil organic N. A cluster of samples from Schinos and Evia exhibited δ15N values close to or higher than 8 ‰, falling in the field of animal and/or human waste; especially for Schinos and given the absence of intensive agricultural practices in this area, it is deduced that domestic sewage is the main source of NO3- in groundwater. On the other hand, isotope data indicated that nitrification of NH4+-based fertilizers is responsible for the high NO3- concentrations measured in groundwater from Thiva, and partially from Evia. The high [NO3-]/[Cl-] ratios identified in these water samples signified the chemical fertilizers as the principal source of dissolved NO3-. No clear relationship could be established between Cr(VI) and NO3- in this study when the entire data set was taken into account; several samples with elevated Cr(VI) concentrations exhibited low NO3- concentrations and vice versa. Nonetheless, we found a significantly positive correlation between these solutes in the case of Schinos groundwater system (r=0.83, p=0.005) which might indicate an enhanced Cr(VI) generation when sewage wastes interfere with Cr-containing ultramafic source material. For Evia and Thiva groundwaters, the nitrification of NH4+ in fertilizers, as evidenced by the isotope data of δ15Ν and δ18Ο in NO3-, could be responsible for the production of environmentally relevant amounts of Cr(VI) because the increased concentrations of H+ may increase the mobility of Cr(III) and its subsequent oxidation on Mn oxides (Mills et al., 2011). Although, it is difficult to support a direct link between the isotope data and Cr(VI) concentrations (Fig. 1), it appears that the process of nitrification, either from human/animal waste or synthetic fertilizers, trigger the geochemical occurrence of geogenic Cr(VI) in groundwater. Both NO3- and Cr(VI) occur primarily in oxic groundwater, deduced by the high Eh and dissolved oxygen (DO) values measured in the samples, providing a deciding geochemical environment that promotes the persistence of these constituents in solution. Locally in the aquifer, decreasing DO concentrations along flowpaths favor the process of denitrification. This is evident in one groundwater sample from Schinos (δ15Ν and δ18Ο values of 21.5 ‰ and 15.3 ‰, respectively) that exhibited the lowest Cr(VI) concentration (8 μg/L) determined in the data set. The results of this study assist in the clear identification of NO3- contamination origin and provide science-based information to the general public and municipal key stakeholders for a more effective water management planning.

ABSTRACT. Geochemical environmental monitoring, as a prerequisite for environmental risk assessment, is crucial in abandoned mining and mineral processing sites, where one of the most important environmental problems relates to the disposal of extraction waste, as well tailings, directly into streams or at the edge of them, the generation of acid mine drainage and the resulting environmental pollution of soils, stream sediments, surface and underground waters. However, in most of the cases, environmental monitoring is severely restricted, due to the chronic lack of funds and consequently environmental geochemists need of a cost-saving alternative method to classical laboratory analysis programs, dealing efficiently with remote or harsh field conditions. Nowadays, portable X-ray fluorescence (pXRF) analyzers are a key technique for investigating in a wide range of fields (Lemiere, 2018), as they have introduced real – time data into the field, making it possible to create real-time geochemical mapping of areas, to identify elements of interest and to gain an understanding of the trends in elemental soil or sediments pollution. This paper explores the potential for a wider use of Field Portable X-Ray Fluorescence Spectroscopy instruments (pXRFs) in geochemical environmental assessment, in the abandoned Kirki mine area, northern Greece. The results demonstrate that handheld XRF analyzer in the Kirki mine area, has provided a rapid and practical tool for fast, real-time, cost-effective environmental surveys for heavy metal dispersal in a short period of time

ABSTRACT. Recent technical developments in nanometrology have shown great potential for the quantification and characterization of nanoparticles in complex environmental samples. This work aims to identify nanoparticles in the marine environment, appoint sources to each material, and quantify their presence and persistence in the sea water. For that purpose, a comprehensive toolbox will be developed for comparing the physicochemical characteristics and population dynamics of engineered, incidental, and natural nanoparticles.

ABSTRACT. 1.Introduction Quaternary sea level cycles are well imprinted in the marine sediments of continental margins worldwide. The Aegean hosts several locations where excellent preservation of these cycles is manifested on seismic reflection records (Lykousis, 2009; Anastasakis and Piper, 2013). Seismic records of medium and high resolution are not capable to fully resolve and describe the complete association of sedimentary lithofacies that normally develop around 4th and 5th order sea level fluctuations. This is only possible by direct sampling and studying of the sedimentary sequences formed in response to sea level fluctuations. Reworking of the sediments can locally distort the lithostratigraphic continuity, but such processes can readily be identified on the basis of textural and compositional parameters.

2.Objectives The objective of this study is to establish a core transect across the outer shelf and shelf break of the SaronikosGulf in order to establish and evaluate the sedimentary sequences developed during the last sea level cycles. Compositional and textural parameters are established in relation to the sea level curve.

3.Methodology Four gravity cores (SAR3,4,5 and6)presented in this study were retrievedby the Department of Historic Geology-Paleontology, during the 2011 Saronic research expedition utilizing a trawler boat. The cores were scanned for their magnetic susceptibility, split and photographed. Cores were sampled at a few cm resolution based on macroscopic and susceptibility differentiations. Samples wereoven dried at 45oC. Carbonate content (%) was measured on all samples following the Muller and Gastner (1971) method.Organic carbon content was measured on selected samples using a combustion technique. Selected samples were also picked for grain size analysis. Core SAR5,recovered at160m water depth, which displays the well-established EasternMediterranean lithostratigraphy,was chosen for detailed X-ray bulk mineralogy. Carbonate minerals were estimated by measuring peak areas of main peaks on diffractograms and utilizing published calibration curves. Other well crystallized minerals were measured using peak heights and mineral correction factors (Muller and Mann, 1979).

4.Results SAR-3 was recovered at 110 m depth and is entirely composed of bioclastic sands dominated by coarse calcareous algae fragments, bivalves and gastropods. Carbonate contents range in-between 60-80%. At the base of the core an unconformity is observed. The basal section of this core displays a significant percentage of well rounded, sub-spherical terrigenous grains, plus many iron-coated mostly foraminifera tests. Coarse biogenic grains are broken and rounded. All the above suggest exposure to a sub-aerial wave dominated coastal environment. SAR-4, retrieved at 138 m depth, consists of medium to fine carbonate sands with frequent large sized shells. Generally carbonate contents are decreasing upwards ranging from 50-70%. SAR-5 obtained at 160 m depth, on the slope, displays well developed cyclothematic lithoface associations starting from the bottom with coarse grained carbonate sands,enriched on biogenic fragments andtheir carbonate content to rangefrom 90% at the base to 55% on the top of the core. A well developedsapropelic layer is developed on the upper section of the core. Grain size mean diameters are around-1φat the lower half of the core, due to coarse biogenic tests and rapidly decrease upwards from below the sapropelic sequence to the top of the core. There is also a concomitant to the grain size decrease in carbonate contents. Detailed bulk mineralogy of this core also displays well expressed trends. Terrigenous minerals score highest percentages at the upper section of this core. Illite is the most dominant mineral varying from 3 to 17 %, quartz is the second in abundance scoring 2-16% respectively. There are two levels with enhanced feldspar contents, around 7%, most likely associated with cryptotephras. Carbonate minerals consist mostly from Mg-rich calcite, calcite and aragonite while dolomite is present in trace amounts. From top of the core until below the sapropelic layer Mg-calcite varies from 20-38%, calcite scores 16-21% and aragonite varies from 6-15%.At a well expressed stratigraphic interval below the sapropelic lithoface, there is a coarse calcareous algae sand lithoface that presents aragonite contents up to 32%. Below this layer, there is a step-wise increase of Mg-rich calcite paralleled by a concomitant decrease of calcite and aragonite. Mg-rich calcite scores up to 74%. SAR-6 is located at 212 m depth within the basin of South Saronikos. It is generally composed of a fine sandy marl with carbonate contents generally decreasing upwards from 65-45%. A thin 6 cm sapropelic horizon is developed on the uppermost section, from 26-32 cms. Carbonate contents score the highest percentages of 68% around 10-20 cm below the sapropelic layer and then steadily decrease to the bottom of the core varying in-between 40-50%. Grain size shows little variability along this core with the finest sediments attaining median diameters of around 3,7φ at the top 10 cm. An indicative high resolution chirp profile along the bathymetric transect established along the coring stations presented in this study shows: a.a 8-20 m thick horizon developed in water depths greater than 190m. b.a less than 1m thick surface horizon developed in-between 190-120m. c.a clinoform package developed at 115-120 m attributed to the last glacial sea level strandline. This clinoform package is bounded to the north by a ca 5-m high sandy barrier.

5.Conclusions A bathymetric transect,in-between water depths of 110-212 m, obtained by coring stations along the South Saronikos shelf revealed the following: 1)There is direct evidence of subaerial exposure in core SAR-3 recovered in water depth of 110 m. Terrigenous grains at the time of this exposure suggest littoral transport along this paleo-coast presumably developed during the last glacial sea level drop as mapped on seismics by the identification of a clinoform wedge at 115-120 m. 2)Cores recovered down to water depths of around 140m display a coarse sandy carbonate facies. 3)Deeper cores display cyclothematic lithofacies associations with a thin sapropelic layer developed in the upper 30 cm. Texture of sediments becomes coarser below the uppermost sapropelic horizon, as a result mostly of coarser biogenic grains precipitated in shallower water depths during reduced sea levels of MIS 2 and 3. There appears to be terrigenous sediment trappinglandwards to the north, behind a sediment barrier developed in Saronikos shelf during the lowest and lower sea levels. 4)Mg-calcite contents at a core recovered at 160 m w.d. display slightly reduced percentages at the colder stratigraphic interval of MIS 2 and further show a drastic increase throughout MIS 3 as compared to MIS 1. This paradox can be attributed to the enhanced contribution to the biogenic carbonate factory of Mg-calcite secreting organisms, such as coralline red algae, bryozoans and echinoids. This is due to the fact thatMIS 3 sea level consisted of an initial rise to alevel of approximately 60 m for the first half of MIS 3 andsubsequent drop to 80 m for the remainder.

References Anastasakis, G., Piper, D.J.W., 2013. The changing architecture of sea-level lowstand deposits across the Mid-Pleistocene Transition: South Evoikos Gulf, Greece. QuaternaryScience Reviews 73, 103–114. doi:10.1016/j.quascirev.2013.04.018 Lykousis, V., 2009. Sea-level changes and shelf break prograding sequences during the last 400ka in the Aegean margins: Subsidence rates and palaeogeographic implications. Continental Shelf Research 29, 2037–2044. doi:10.1016/j.csr.2008.11.005 Mann, U., Müller, G., 1979. X-ray mineralogy of Deep Sea Drilling Project Legs 51 through 53, western North Atlantic. Initial Rep. Deep Sea Drill. Proj. 51–53, 721–729. Müller, G., Gastner, M., 1971. The “Carbonate Bomb, a simple device for the determination of the carbonate content in sediments, soils, and other materials. N. Jb. Mineral., vol. 10, pp. 466–469.

ABSTRACT. Soft-sediment deformation structures formed during, or immediately after deposition, during the first stages of the sediment's solidification. These structures are formed mainly in shallow marine areas and in deep basins with the presence of turbiditic currents. This is because these environments have high deposition rates, which allows the sediments to pack loosely. The deformation is related mostly to the drastic decrease in shear resistance in water saturated and unconsolidated sediments. The Cretaceous succession differs between the three sub-basins of the Ionian zone. The lower Cretaceous Vigla limestone in the external Ionian sub-basin, where the studied Kastos Island is situated, consist of white, light grey to yellowish micrites and radiolarian biomicrites (wackestones to packstones and rarely mudstones). Usually they are thin-bedded to platy with chert intercalations and chert nodules. (Skourtsis-Coroneou et al., 1995). In Kastos Island, the lower Cretaceous Vigla formation outcrops on the east side of the island, and consists of, in the lower part, carbonates in restricted outcrops with estimated thickness up to 350 m, whereas the upper part with interbedded cherts and shales (Vigla shales) is up to 100 m thick. The Vigla limestones, consist of thin to medium bedded limestones, with up to three strongly deformed horizons, internally to undisturbed limestones, representing slumps. This deformation appears stronger than in the NW Peloponnesus (Bourli et al., 2019) and is interpreted as syn-sedimentary slumping. According to Bourli et al., (2019) Vigla limestones in NW Peloponnesus are characterized by synsedimentary deformation. On the upper part of this deformation paleo relief filled up by breccia showing that, sedimentation was active during and after the deformation. Measurements of this deformations showed that there is a “fold” axis with E-W direction. Moreover, the steep side of this deformation dips northwards. The above introduce that slumps directed northwards and produced from transfer faults with E-W direction (Fig. 1). In Kastos island and although the estimated thickness for Vigla limestones is about 350m only 30m are outcropped along the eastern cost of the island. Vigla limestones are unconformably underlines Vigla shales and this contact is characterized by strong deformation. This deformation has different laterally thickness ranging from 1 to 3m thick. Such horizons also were recognized internally to Vigla limestones. In two studied sections with NW-SE and SW-SE directions (Figs. 2,3), two different directed slump horizons were recognized. In the NW-SE section, an E-W deformation axis was recognized, probably related with a transfer fault activity; whereas in the SW-NE section deformation is stronger with two or three different directed axes (either N-S or E-W) introducing slump development from both normal and transfer faults activity. It seems that the slumps produced from the normal fault activity are thicker and strongly deformed in contrast to these that produced from transfer faults. Except of Vigla limestones also within Vigla shales slump horizons were recognized. In these horizons paleo relief produced from slumping is up to 40cm (Gianniskari Vigla shales on Bourli et al., 2019); whereas in Kastos Island this paleo relief is up to 1m? or more (Fig. 4). From the above we conclude that in both areas (NW Peloponnesus and Kastos island) Vigla limestones are characterized by intensive deformation during sedimentation due to both normal and transfer faults activity. Further study is needed in order to show how and when this deformation took place. It is obvious that deformations of Vigla shales is lower and the reasons for the above is under investigation.

ABSTRACT. Background The understanding of palaeoenvironmental changes through sedimentological, palaeontological, geochemical and mineralogical studies provide information regarding depositional environments, elemental fluxes, palaeoclimate reconstruction, sea level fluctuation, tsunamigenic phenomena and tectonic activity (Kontopoulos and Avramidis 2003; Vött, et.al., 2009, 2011; Avramidis et al., 2013; Emmanouilidis et al., 2018). Coastal aquatic systems are considered environmentally sensitive areas formed behind sand or gravel barrier shorelines, at the terminal area of the coastal alluvial plains or at river mouths. They are shallow and highly dynamic ecosystems at the interface between coastal and marine environments, which can be permanently open or intermittently closed off. The study of sedimentary facies in lagoonal systems reveal transition patterns concerning sediment runoff, physical erosion in the catchment area, human activity etc. High resolution geochemical profiles, relative changes and altering trends of elemental concentration imprint these palaeoenvironmental changes as well as micro facies that would not be detected otherwise. Many researchers use geochemical proxies such as Rb/Sr, Fe/Mn, Ca/Ti, Sr/Ti, Zr/Rb, Zr/Ti to delineate existing physical, sedimentological and geochemical processes such as evaporation, precipitation, dissolution of solid phases, Eh and pH changes, chemical and physical weathering. Objectives Mouria and Agoulinitsa lagoons are located in western Peloponnese, Greece. Palaeoenvironmental studies conducted in western Greece, reveal continuous transitions in the geomorphological evolution of coastal aquatic systems. Marine inundations, human activity and fluvial influx comprise major aspects into the lifespan of those systems. In this framework, the present study reveals such sedimentary transitions in both studied sites based on sedimentological and geochemical proxies. Methods Two sediment cores were retrieved using an Eijelkamp vibrating corer with closed barrel tubes. After the extraction, the cores were sealed with cling film and transported for analysis in the laboratory of sedimentology, University of Patras, Greece. Standard sedimentological analyses were carried out, on a total of 80 sediment samples including: (1) grain size analysis and calculation of moment measures such as mean, sorting, kurtosis and skewness, (2) color determination and RGB profile plot, (3) Total Organic Carbon (T.O.C.), (4) Total Carbon (T.C.), (5) Total Nitrogen (T.N.), (6) Calcium Carbonate Content (CaCO3), (7) Total Phosphorus (T.P.) content and (8) Magnetic susceptibility measurements. U-channels were extracted from the sediment cores for XRF core-log analysis using the Avaatech system at the Institute of Geosciences of Kiel University. Core scanning was performed with a Molybdenum tube set at 10 kV and 30 kV with a step of 0.5 cm and an integration time of 60 second per measurement. Results Compiling all the sedimentological and geochemical data, 3 main lithological units were distinguished for Mouria core (Fig. 1) and 2 for Agoulinitsa core. For Mouria core, Units 1 and 2 consist of coarser material and present the highest values in geochemical ratios Si/Ti, Ca/Fe, Sr, Cl, S, Zr/Rb (Fig. 1). The increase of Cl and S indicate the marine influence in the study area whereas Mn/Fe ratio reflects the oxic conditions (Fig. 1). Magnetic susceptibility is mostly associated with terrestrial input in the study area, thus presenting the lowest values at these units (Fig. 1). Unit 3 consist of fine organic rich sediment. Elemental ratios such as Ti and Rb/Sr are strongly associated with clay minerals and provide a clear signal concerning the physical erosion and fine sediment deposition in the study area. Concerning Agoulinitsa core, the two sediment units that were recognized, present similar trends with Mouria core. The first two meters of the core, are characterized by organic rich sediment, presenting high values for the terrigenous elements. Mn/Fe ratio, indicates anoxic conditions, validating the high organic content and thus presents a more lacustrine environment. Sandy units at the lower parts of the core (>2 m) present an open lagoonal environment. Higher values of S, Cl and Br indicate constant marine inundations into the system. Conclusion The sedimentological, geochemical and magnetic susceptibility measurements from both sediment cores (ML-1 and AG-1), indicate different sediment transport and depositional processes. Non-destructive analysis conducted on both cores, imprints all the palaeoenvironmental and palaeogeomorphologial changes that occurred in the study area as well as the interplay between those coastal aquatic systems and marine environment.

ABSTRACT. Background & Approach The Ionian Sea can be distinguished in the northern and the southern part. The north part, above the Kefalonia Transform Fault (KTF), is characterized by the obduction of the Hellenides Thrust and Fold Belt (HTFB) to the Apulian margin (continental crust). The southern segment, south of the KTF, is characterized by the activity of two dextral strike-slip faults, the subduction of a thinned continental-oceanic crust below the HTFB (continental crust) and the development of the Mediterranean Ridge (MR), the Backstop and the Hellenic Trench. The methodology followed was the study of the available literature, the interpretation of the well data and the 2D seismic survey acquired by PGS in 2012, the 2D modelling and the integration in order to establish a framework for the assessment of the hydrocarbon prospectivity. Results & Conclusions: Geological Evolution, Petroleum System and Plays North Ionian Sea covers the southern margin of the greater Apulian platform. Seismic interpretation led to the development of a 2D model that simulates the evolution of the area. The reconstruction enables us to visualize and validate our seismic interpretation. North Ionian Sea has mainly carbonate plays equivalent to the ones in the Adriatic Sea and Italy the source rocks are expected to be Upper Triassic (Burano Fm.), Jurassic (Complesso Anidritico Fm. and Calcare di Aptici Fm.), Toarcian to Aalenian (Rosso Ammonitico Fm.), Late Valanginian to Hauterivian (Maiolica Fm.), Early Aptian (Selli OAE, Marne a Fucoidi Fm.) and Late Santonian to Early Campanian pelagic sediments (shales) (Beicip, 2014; Nikolaou, 2001; Kosmidou, 2018). Geochemical analysis from well samples suggest type I-II oil-prone source rocks with higher TOC values in the Cretaceous and Jurassic series (up to 11.7% and 19.1%); and Triassic shale fragments (up to 16.1%). Play A: Oligocene-Late Miocene shallow-water carbonate build-ups (eq. Castro Fm. and Novaglie Fm.) sealed by fine-grained pelagic marls. The trap is stratigraphic pinch-outs. Analogues are the Giove and Medusa discoveries in Italy. Outcrop data in Italy suggest efficient vertical communication between the Cretaceous karstified reservoir and the overlying Oligocene – Miocene carbonates. Play B: Reservoirs of microbreccious limestone and/or calcareous gravity-mass deposits (slope-fan) with locally bioclastic base-of-slope aprons (eq. Scaglia). The trap is stratigraphic pinch-outs sealed by muddy-cherty deep-sea sediments. The main challenges associated with this play are the lateral extent and the distribution of the reservoir quality properties. Analogue discoveries are the Aquila, Rovesti and Griffone in the Adriatic Sea. Secondarily; Play C: Intra-platform plays rimmed platform deposits/reefs with stratigraphic traps (pinch outs) with lagoonal silty sediments in the Cretaceous series. Play D: Karstified sections sealed by pelagic sediments. The South Ionian Sea is the area offshore western Peloponnese which is subdivided into the MR to the west and the HTFB and its offshore extension. important unconformities (Burdigalian and Messinian) and mass transport deposits overlie the Mesozoic carbonates. The depositional environment is shallow marine/platform (eq. Gavrovo Fm. and Paxi Fm.) changing westwards to distal slope and deformed ramp anticlines have been interpreted. The presence of the Apulia platform south of the KTF is estimated only in offshore Kefalonia. The Burano evaporites play a key role as a decollement but they are found in three main geometric configurations: in place, as diapirs, and reworked. They are believed to have facilitated the migration of the hydrocarbons in the carbonate reservoirs. The Messinian evaporites are deformed, due to the westward movement of the MR. Both Triassic and Messinian evaporites act as cap rock in specific leads. The Backstop is the extension of the lower Hellenic continental margin and its geometry is a pop–up structure with a flat summit. Geophysical data suggest a unit of high seismic velocity. To the west, there is the MR, an accretionary wedge with fluidized mud from the decollement zone(s). The upper part is characterized by highly deformed Plio- Pleistocene sediments and Messinian Evaporites. There are signs of two decollement levels and structural elements in the Mesozoic carbonate units. The area is highly tectonized with intensive shortening and imbrication. The plays are mainly carbonate with clastic plays in channels originated from the Hellenides. The carbonate plays can be summarized in the following: Type A: Carbonate slope deposits/ reefs; the reservoirs are expected to be of Middle Jurassic - Eocene age charged by thermogenic mature type I-ΙI source rocks Lower Cretaceous Vigla shales and Triassic Breccias. Type B: Carbonate faulted blocks with karstified tops sealed by evaporitic and shale deposits. It is believed to have the same source rocks as Play type A. Type C: Middle-Upper Pliocene intercalations of (calcareous) sandstone and shales/siltstone with gas shows with expected source rock in the Paleogene-Neogene clastic basins. References Beicip Franlab, 2014. New Exploration Opportunities in Offshore Western Greece and South of Crete. Kosmidou, V., Bellas, S., Bassias, Y., 2018. Offshore Western Peloponnese: Structural Elements and differences from Northern Ionian, Greece. First EAGE Workshop on Geophysical and Geological Challenges in the Hydrocarbon Provinces of the Eastern Mediterranean, St. Julian’s, Malta. Kosmidou, V., Makrodimitras, G., Papatheodorou, N., 2018. Depositional Environments and Hydrocarbon Potential of Northern Ionian Sea. AAPG GTW Alpine Folded Belts and Extensional Basins, Granada, Spain. Nikolaou, K.A., 2001. Προέλευση και Μηχανισμός Μετανάστευσης των Κυριότερων Ενδείξεων Υδρογονανθράκων της Δυτικής Ελλάδας. Bulletin of the Geological Society of Greece, Vol. XXXIV/3, Proceedings of the 9th International Congress, Athens, Greece, p. 1213-1219

ABSTRACT. According to Bourli et al., (2019) upper Cretaceous–Lower Eocene deposits of the Ionian basin is the major target in hydrocarbon exploration as they represent the expected reservoir rocks. These deposits are mostly composed of calciturbidites interbedded with breccia-microbreccia deposits. Calciturbidites can be of great economic importance and they can serve as viable reservoir rocks because of their high porosity and permeability values, which can be additionally enhanced by the development of nodules that in turn increase secondary porosity. Studied Cretaceous limestones in Araxos peninsula (NW Peloponnesus, internal Ionian sub-basin) and Kastos Island (external Ionian sub-basin) showed that both lower Cretaceous “Vigla limestones” and upper Cretaceous “Senonian limestones” are characterized by the presence of siliceous nodules. Siliceous nodules within the Vigla limestones are of smaller in relation to the Senonian limestones. The above difference in nodules size could be related with the different porosity of hosted deposits. Pelagic limestones of lower Cretaceous Vigla limestones must have reduced pores or lower porosity than the porosity of calciturbidites. Nitrogen absorption-desorption was performed with the Quantachrome Nova 2200e at the Research Laboratory of Minerals and Rocks, Department of Geology, University of Patras. The relative pressure against the nitrogen adsorption was used and a full isotherm diagram was produced based on the adsorption and the desorption isotherms. For determination of the specific surface area, the BET equation (Brunauer, Emmett, & Teller, 1938) was used in the form of a linear plot. The BJH method (Barrett, Joyner, & Halenda, 1951) was applied within the range from 2 to 50 nm and average cumulative surface of pores (SBJH), average volume of mesopores (VBJH) and average diameter of mesopores (DBJH) were calculated. According to IUPAC (Sing et al., 1985), pores are classified into three groups according to their diameter: micropores (diameter < 2 nm, mesopores (diameter 2 - 50 nm), and macropores (diameter > 50 nm). Moreover, results processing with software NovaWin helped us in order to classify isotherms according to Sing et al. (1985), where five (5) groups (I to V) were determined and isotherm hysteresis loops into four types (H1-H4). Lower Cretaceous limestone samples (V1, V3, I5, GN1 and GN2) and Upper Cretaceous limestone samples (S1, Ark7 and Ar40d), from both studied areas were analyzed for their specific surface area (SBET) and the average diameter of mesopores (DBJH) by Nitrogen porosimetry. Porosity measurements for both areas showed that the isotherms of the samples, according to IUPAC classification (Sing et al., 1985), are type IV, indicating mesoporous (2 – 50 nm) studied rocks. The characteristic feature of type IV isotherm is the presence of the hysteresis loop, typical for the mesoporous material, which is associated with pore condensation (Fig. 1). The hysteresis loop of the studied type IV isotherms classified in the H3 type, indicating pores with slit shape overall of the sample, from non-rigid aggregated of platy particles. Also, if the network consists of macropores, then these are not completely filled with the condensate (Thommes et al., 2015). Furthermore, the H3 loop hysteresis suggests the presence of mainly accessible pore network, because otherwise it would not create hysteresis (Liu et al., 2014). The adsorption and desorption branches of some samples approach a nearly vertical direction above the 0.8 relative pressure indicating the presence of outer surface, which is characteristic of isotherm II (red circle in figure 1A). The above could support the idea that although the studied samples were classified into the type IV due to the presence of the hysteresis loop, the pores present broad size distribution and could also suggest the presence of some larger porous, perhaps of type II. In cases where an incomplete equilibrium during the measurements occur, an open loop hysteresis is observed (Bertier et al., 2016) at very low relative pressure (red circle in Fig. 2) that refers to the slow diffusion of adsorptive in micropores, structural deformation of the sample or even chemisorption (Rouquerol et al. 2014). On the other hand, the hysteresis loop for the rest of the samples has a narrower shape indicating the presence of slit-shaped mesopores with a non-uniform size (see red box in Fig. 1B). Nitrogen sorption isotherms of the studied samples have similar shape, classified as an H3 of the type IV isotherm. According to the BJH method the pore volume (VBJH) ranges from 0.001 to 0.002 cc/g, the pore diameter (DBJH) ranges from 3.550 to 3.663 nm and the cumulative surface area (SBJH) ranges from 0.376 to 0.826 m2/g while the total specific area (SBET) through the BET calculations ranges from 0.577 to 0.933 m2/g. Only one sample had different values as far as the BJH pore volume (0.007 cc/g) and the BJH cumulative surface area (2.321 m2/g), even though the BJH pore diameter is 3.550 nm, while the BET specific surface area with the BET calculation is 3.193 m2/g. According to the above and taking into account that both, Early Cretaceous Vigla limestones and Late Cretaceous Senonian calciturbidites, showed that now they are mesoporous, a secondary higher increase of pores within Early Cretaceous Vigla limestones than in Late Cretaceous calciturbidites, could be caused due to fracturing owed to the nodules development, as suggested by Spence and Finch (2015).

ABSTRACT. The Messinian was a period of drastic paleoenvironmental and paleoceanographic changes in the Mediterranean. During this time interval, tectonic processes together with glacio-eustatic sea level oscillations led to the Mediterranean isolation from the Atlantic Ocean triggering the formation of thick evaporite successions during the so-called “Messinian Salinity Crisis” (MSC, 5.97-5.33 Ma; Krijgsman et al., 1999; Roveri et al., 2014). Studies of Messinian sediments preserved in marginal and/or peripheral Mediterranean sub-basins have provided much information on the sedimentology, cyclostratigraphy, palaeontology, and geochemistry of that period (Karakitsios et al., 2017a,b; Moissette et al., 2018; Antonarakou et al., 2019; Vasiliev et al., 2019). Especially the cyclic bedded biosiliceous deposits of the Tripoli Formation that preceded the MSC (6.96-5.98 Ma) records an important depositional change that occurred after the monotonous deposition of Tortonian to lowermost Messinian marls in deep open marine conditions, and consists of lithological alterations of marls, limestones, diatomites and organic-rich sapropelitic layers. Overall, this typical Late Miocene cyclic succession likely resulted from orbitally-driven variations in freshwater input due to the African Summer Monsoon modifications, reflects precessionally-controlled dry-wet climate fluctuations influencing the hydrological budget of the entire Mediterranean Sea (Rohling et al., 2015).

We present the first continuous non-diatomaceous Messinian record in eastern Mediterranean based on the combined sedimentological, micropaleontological, and geochemical approach, recovered from sampling the Agios Myron section. The study section, is located in the north-central Crete, and consists of a continuous, pelagic sedimentation (alternations of hemipelagic homogenous marls and sapropels) covering the ∼7.2-6.5 Ma time interval. To ascertain the potential correlation between the increase in calcareous sediments on Crete and the beginning of the diatomite sequences on Gavdos, we further compare our results from the time-equivalent interval with one of the most suitable, well-astronomically dated, and complete Miocene sections in the Mediterranean Sea, the Metochia section (Schenau et al., 1999; Drinia et al., 2007). An integrated correlation between Agios Myron and Metochia sections is shown in Figure 1. The sections were correlated using their characteristic sedimentary cyclic pattern, planktonic foraminiferal biostratigraphy and the ash layers. Both sections were characterized by the same sedimentary cluster pattern, with the only difference of the presence/absence of the diatomite sequence at the top. The characteristic sedimentary cycles have been also correlated to the astronomical target curve, in particular the precession interference pattern in isolation curve. Astronomically calibrated biostratigraphic events were used as reference points in order to check the correct sequence of sedimentary cycles. We have identified 3 planktonic foraminiferal bioevents: the First and the Last Common Occurrence (FCO and LCO) of Globorotalia nicolae and the re-appearance of Globorotalia miotumida group (Fig. 1). We also detected two different tephra layers in the Agios Myron section: the Cretan ash-layers 1 and 3 which have an astronomical age of 6.941 Ma and 6.771 Ma respectively (Hilgen et al., 1997; Kuiper et al., 2004). The resulting integrated stratigraphy for the lower Messinian at Agios Myron, including biostratigraphy, cyclostratigraphy, and tephrostratigraphy, is consistent with both bio- and magneto-stratigraphic dated pre-MSC sections in eastern Mediterranean Sea. Finally, we further complement this study with stable isotope (δ18O, δ13C) and distributional planktonic foraminiferal data with the aim to monitor the mutual interplay between paleoclimatic/paleoceanographic evolution and the sedimentary environment across the pre-MSC time interval in this marginal setting.

References Antonarakou, A., Kontakiotis, G., Vasilatos, C., Besiou, E., Zarkogiannis, S., Drinia, H., Mortyn, P.G., Tsaparas, N., Makri, P., Karakitsios, V., 2019. Evaluating the effect of marine diagenesis on Late Miocene pre-evaporitic sedimentary successions of eastern Mediterranean Sea. IOP Conference Series: Earth and Environmental Sciences, 221: 012051 doi:10.1088/1755-1315/221/1/012051. [Journal Article] Drinia, H., Antonarakou, A., Tsaparas, N., Kontakiotis, G., 2007. Palaeoenvironmental conditions preceding the Messinian Salinity Crisis: A case study from Gavdos Island. Geobios, 40, 251–265. [Journal Article] Hilgen, F.J., Krijgsman, W., Wijbrans, J.R., 1997. Direct comparison of astronomical and 40Ar/39Ar ages of ash beds: potential implications for the age of mineral dating standards, Geophys. Res. Lett., 24, 2043–2046. [Journal Article] Karakitsios, V., Roveri, M., Lugli, S., Manzi, V., Gennari, G., Antonarakou, A., Triantaphyllou, M., Agiadi, K., Kontakiotis, G., Kafousia, N., de Rafelis, M., 2017a. A record of the Messinian salinity crisis in the eastern Ionian tectonically active domain (Greece, eastern Mediterranean). Bas. Res., 29, 203–233. [Journal Article] Karakitsios, V., Cornée, J.-J., Tsourou, T., Moissette, P., Kontakiotis, G., Agiadi, K., Manoutsoglou, E., Triantaphyllou, M., Koskeridou, E., Drinia, H., Roussos, D., 2017b. Messinian salinity crisis record under strong freshwater input in marginal, intermediate, and deep environments: The case of the North Aegean. Palaeogeogr., Palaeoclimatol., Palaeoecol., 485, 316–335. [Journal Article] Krijgsman, W., Hilgen, F.J., Marabini, S., Vai, G.B., 1999. New paleomagnetic and cyclostratigraphic age constraints on the Messinian of the Nothern Apenines (Vera del Gesso Basin, Italy). Mem. Soc. Geol. It., 54, 25–33. [Journal Article] Kuiper, K.F., Hilgen, F.J., Steenbrink, J., Wijbrans, J.R., 2004. 40Ar/39Ar ages of tephras intercalated in astronomically tuned Neogene sedimentary sequences in the eastern Mediterranean. Earth Planet. Sci. Lett., 222, 583–597. [Journal Article] Moissette, P., Cornée, J.-J., Antonarakou, A., Kontakiotis, G., Drinia, H., Koskeridou, E., Tsourou, T., Agiadi, K., Karakitsios, V., 2018. Palaeoenvironmental changes at the Tortonian/Messinian boundary: A deep-sea sedimentary record of the eastern Mediterranean Sea. Palaeogeogr. Palaeoclimatol. Palaeoecol., 505, 217–233. [Journal Article] Rohling, E.J., Marino, G., Grant, K.M., 2015. Mediterranean climate and oceanography, and the periodic development of anoxic events (sapropels). Earth-Sci. Rev. 143, 62–97. [Journal Article] Roveri, M., Flecker, R., Krijgsman, W., Lofi, J., Lugli, S., Manzi, V., Sierro, F.J., Bertini, A., Carnerlenghi, A., De Lange, G., Govers, R., Hilgen, F.J., Hubscher, C., Meijer, P.T., Stoica, M., 2014. The Messinian Salinity Crisis: Past and future of a great challenge for marine sciences. Mar. Geol., 352, 25–58. [Journal Article] Schenau, S.J., Antonarakou, A., Hilgen, F.J., Lourens, L.J., Nijenhuis, I.A., Van Der Wejden, C.H., Zachariasse, J.W., 1999. Organic rich layers in the Metochia section (Gavdos, Greece): Evidence for a single sapropel formation mechanism in the eastern Mediterranean during the last 10 Myr. Paleoceanography, 153, 117–135. [Journal Article] Vasiliev, I., Karakitsios, V., Bouloubassi, I., Agiadi, K., Kontakiotis, G., Antonarakou, A., Triantaphyllou, M., Gogou, A., Kafousia, N., de Rafélis, M., Zarkogiannis, S., Kaczmar, F., Parinos, C., Pasadakis, N., 2019. Large sea surface temperature, salinity, and productivity-preservation changes preceding the onset of the Messinian Salinity Crisis in the eastern Mediterranean Sea. Paleoceanography and Paleoclimatology. 34. [Journal Article]

ABSTRACT. Introduction-Geological setting The middle Eocene to early Oligocene transition (EOT) is of particular interested because it corresponds to significant climatic changes in the Cenozoic (Maravelis and Zelilidis, 2012). The EOT marks the shift from greenhouse to icehouse conditions and the last major extinction of marine fauna (Miller et al., 1992). Calcareous nannofossils are abundant in submarine fan deposits and are regarded as very good biostratigraphic indicators (Winter and Siesser, 1994). Thus, calcareous nannofossil analysis has been employed for determining the age of such sediments. The submarine fan deposits in the Pindos Foreland Basin, western Greece offer a case study to precisely define the EOT and investigate potential fingerprints of this climatic change at low latitude settings. The basin is bounded to the east by the Pindos Thrust and to the west by the Ionian thrust and is further dissected by smaller thrusts (Gavrovo, internal and middle Ionian thrusts). Although the studied deposits are Eocene to Oligocene in age, detailed biostratigraphic analysis to define their time span has not been yet conducted and the EOT has not been documented. In view of the absence of such data, calcareous nannofossil analysis has been carried out, adding constraints on the depositional age of the submarine fan deposits in Pindos Foreland Basin and documenting the EOT in western Greece.

Material and methods For calcareous nannofossil analysis, 70 samples were collected from the submarine fan deposits in Pindos Foreland Basin. These deposits correspond to the infill of the basin, as a result of the growing Pindos Thrust (Konstantopoulos and Zelilidis, 2012). The submarine fan system documents progradation and therefore, outer fan deposits are stratigraphically below inner fan sediments (Konstantopoulos and Zelilidis, 2012). Prior to sample selection and collection, systematic field work was performed to assure that the samples are placed to the right stratigraphic position and cover the entire sedimentary succession. The sample preparation was made using standard smear slide techniques, as described in Bown and Young (1998) and Giunta et al. (2003). Smear slides were analyzed with an optical Optica Italy B-1000POL microscope at 1250× magnification. Calcareous nannofossils were generally abundant and well preserved. The biostratigraphy was based on the biozonal definitions of Martini (1971) and Agnini et al. (2014).

Results and conclusions The biostratigraphic analyses of more than 70 samples in outer fan deposits, until now, calcareous nannofossils (fig.1; fig.2) confirm the late Eocene to early Oligocene time interval. The studied samples referred to a 221 m total sequence that rest uncomfortably over the Eocene limestones. The transition zone from carbonates to clastic deposits showed a late Eocene age. The Eocene-Oligocene boundary is observed in the lower part of the turbiditic system. In particular, the presence of Discoaster barbadiensis, Discoaster saipanensis, Ericsonia formosa, Cyclicargolithus floridanus, Reticulofenestra floridana, and Sphenolithus predistentus confirms late Eocene. The presence of C. floridanus, Reticulophenestra bisecta, R. floridana, S. predistentus, Sphenolithus distentus and Sphenolithus ciperoensis in combination with the absence of D. barbadiensis, D. saipanensis indicates the early Oligocene time interval in the middle/upper part of outer fan deposits. In conclusion, the sedimentation in western Greece started on late Eocene and continues on early Oligocene. Subsequently, further investigation is to be conducted for: • The biostratigraphic analysis of outer and inner fan deposits using calcareous nannofossils and planktonic foraminifera. • The foraminiferal analysis (both planktonic and benthic foraminifera) because of the palaeoclimatological, palaeoenvironmental and palaeoecological interest of Eocene-Oligocene epoch.

Acknowledgements This work was funded by the H.F.R.I. (Hellenic Foundation for Research & Innovation) and GSRT (General Secretarial for Research and Technology) through the research project “Global climate and sea-level changes across the Latest Eocene-Early Oligocene, as reflected in the sedimentary record of Pindos foreland and Thrace basin, Greece, 80591”.

References Agnini, C., Fornaciari, E., Raffi, I., Catanzariti, R., Pälike, H., Backman, J. Rio, D. 2014. Biozonation and biochronology of Paleogene calcareous nannofossils from low and middle latitudes. Newsletters on Stratigraphy 47, 131–181. Bown, P.R., Young, J.R., 1998. Techniques, in: Bown, P.R. (Ed.), Calcareous Nannofossil Biostratigraphy. British Micropalaeontology Society Series. London, UK: Chapman & Hall, p. 16-28. Giunta, S., Negri, A., Morigi, C., Capotondi, L., Combourieu-Nebout, N., Emeis, K.C., Sangiorgi, F., Vigliotti, L., 2003. Coccolithiphorid ecostratigraphy and multi-proxy paleoceanographic reconstruction in the Southern Adriatic Sea during the last deglacial time (Core AD91-17). Palaeogeography, Palaeoclimatology, Palaeoecology 190, 39-59. Konstantopoulos, P., Zelilidis, A., 2012. Sedimentation of submarine fan deposits in Pindos foreland basin, from late Eocene to early Oligocene, West Peloponnesus peninsula, Greece. Geol. J., doi:10.1002/gj.2450. Maravelis, A., Zelilidis, A., 2012. Paleoclimatology and paleoecology across the Eocene–Oligocene boundary, Thrace Basin, northeast Aegean Sea, Greece. Palaeogeography, Palaeoclimatology, Palaeoecology 365-366, 81-98. Martini, E., 1971. Standard Tertiary and Quaternary calcareous nannoplankton zonation, in: Farinacci, A. (Ed.), Second Planktonic Conference Proceedings, Roma 1970. Second Planktonic Conference Proceedings, Roma 1970. Rome: Edizioni Tecnoscienza, p. 739-785. Miller, KG. 1992. Middle Eocene to Oligocene stable isotopes, climate and deepwater history: The Terminal Eocene Event? See Prothero and Berggren 1992, pp. 60-77. Pälike, H., Norris, R.D., Herrle, J.O., Wilson, P.A., Coxall, H.K., Lear, C.H., Shackleton, N.J., Tripati, A.K., Wade, B.S. 2006. The heartbeat of the Oligocene climate system. Science 314(5807), 1894-1898. Winter, A., Siesser, W.G., 1994. Coccolithophores. Cambridge University Press, 242. Zachos, J., Pagani, M., Sloan, L., Thomas, E., Billups, K., 2001. Trends, rhythms, and aberrations in global climate 65 Ma to Present. Science 292, 686-693.

ABSTRACT. Background Coastal lakes and lagoons are highly dynamic and prone to changes like human impact, climatic influences or changes in depositional environments and many more all of which are imprinted in the sediment characteristics and chemistry. Grain size distribution and moment measurements provide an insight into transport-deposition processes while pointing out driving forces (Gao and Collins, 1992; le Roux, 1994,). Sedimentological analyses are generally coupled with geochemical focusing on major oxides, trace elements as well as mineralogy which provide information concerning the provenance and geochemical processes of the sedimentological basement (Panagiotaras et al., 2012). Preserved organic matter in sediments comprises carbon assessed mainly as Total Organic Carbon (TOC) and nutrients as Total Phosphorus (TP) and Total Nitrogen (TN) with organic as well as inorganic sources.

Objectives Vouliagmeni is a coastal lake located in the SW Perachora peninsula extending into the eastern Gulf of Corinth (Greece) while with a maximum depth of around 49m (Katsanevakis, 2005). At the northern and southern part of the lake, due to normal dipping faults, the lake is characterized by steep bathymetry unlike the eastern and western part where the transition is smoother. Until the late 19th century the lake was separated from the Gulf of Corinth by an isthmus when a narrow (18m) canal was constructed leading to the present lagoonal state. In the current study we present a spatial characterization of the lake bottom sediments based on sedimentological, geochemical and mineralogical analyses providing an insight into depositional environments and processes presently active in the lagoon.

Methods A total of nineteen (19) samples consisting of upper 1-2cm lake bottom sediments were collected. For the grain size analysis, coarser material (>4 Φ) was dry sieved whereas finer (<4 Φ) was measured with the use of a Malvern Mastersizer 2000 followed by the moment measures’ calculation using GRADISTAT V.4. (Blott and Pye, 2001). The CaCO3 content was measured with a FOG II/Digital hand-held soil calcimeter (BD Inventions), the TOC using the (Walkley and Black 1934, Avramidis et al., 2015) tritation method, TN content was measured using a Carlo Erba CHNS-O EA 1108 Elemental Analyzer while the TP content was measured using a HACH photometer, based on APHA 2005-4500-P. In a geochemical framework, concentrations of 10 major elements (Si, Al, Ca, Mg, Mn, P, Fe, Na, K and Ti) and 19 trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Hf, W, Pb, La, Ce and Th) were measured by comparison of X-ray intensities for each element with calibration lines constructed from the analysis of known concentrations in 32 international standards. Powdered samples where pressed into pellets and analyzed with a RIGAKU ZSX PRIMUS II wavelength dispersive spectrometer equipped with a 4KW Rh X-ray tube which is located at the Laboratory of Electron Microscopy and Microanalysis of the University of Patras, Greece. A predominant mineralogical composition was determined for each of the nineteen samples by powder X-Ray diffraction (XRD) using a Bruckner D8 advance diffractometer with Ni-filtered CuKα radiation and analyzing the results with the DIFFRACplus EVA 12 software.

Results The central part of the lagoon is characterized by fine sediment, whereas the shallower parts of the lagoon are mostly associated with coarser material. In samples located near the artificial channel and at the north east part of the lagoon, the coarser material is attributed to bivalve assemblages. These bivalve assemblages, which represent around the 70 % of these samples, are highly linked to the hydrological regime of the lagoon, since they show clear evidence of transport before their burial (broken bivalves, cracks). Samples from depth less than 20 m present higher CaCO3 being attributed to the high presence of micro-macrofaunal assemblages (fig. 1d). Low CaCO3 content is apparent in the deep horizons of the lake. Higher TOC, TN and TP concentrations are observed in the depths beyond 20m sediments (fig. 1a, b, c). Statistical analysis on the geochemical data shows that all elements are associated with the organic content and the clay fraction of the sediments except that for Na, Sr and Co. High correlation (r>0.83) for Ni, Cu, Pb, Zn and Rb with the Al2O3 shows the same origin of these metals and their association with the detrital materials from the catchment. The elements Fe, Mn, Mg, K, Ti, P and TP are well correlated with the aluminosilicate fraction of the sediments. However, Ca and CaCO3 show complex geochemical association with high negative loadings (r>-0.95) been observed with Al2O3. Negative loadings (r=-0.56 and r=-0.66) have been found between TOC and CaCO3 and TOC and CaO respectively. This finding implies both a non biogenic and a biogenic origin of these components. The same geochemical feature is observed with the TN. High positive correlation (r=0.83) is found between TOC and TN and also a positive correlation is apparent (r=0.66) between TN and Al2O3. The mineralogical composition showed little spatial diversity throughout the samples and was mostly represented by Quartz (mean: 33.7%), Aragonite (mean: 30.5%), Calcite (mean: 18.2%), Biotite (mean: 13.7%), Halite (mean: 6.5%) and Pyrite (mean: 11.4%, in samples 5,6,7) indicating anoxic/hypoxic conditions.

Conclusions Based on grain size analysis, sedimentological, geochemical and mineralogical analyses a division of the lake in two distinct environments by depth is recognized, shallow (0-20m) and deep (>20m). The grain size distribution, from coarse to fine progressing from the coast (until 20m) to the deeper part is controlled by the hydrodynamic regime. The oxidation conditions in the deep part due to the preservation of organic matter as well as the existence of Pyrite below 35m indicate anoxia.

ABSTRACT. The Aegean system and Continental Greece are marked by back-arc extension that is commonly viewed as occurring in two stages: 1/ classical back-arc extension with N150 normal faults (e.g parallel to the trench) during miocene 2/ followed by mainly N50 dextral strike-slip (North Anatolian fault-NAF) with E-W normal faults (Gulf of Evvia and Corinth) since 5 Ma marking the impact of the NAF in the tectonic system (Armijo et al., 1999; Hubert-Ferrari et al., 2002). However, some published structural data in the Cyclades show that N50 dextral strike-slip were already active during mid-Miocene time (e.g. during granite intrusion between 15 and 10 Ma; Kokkalas and Aydin, 2013), questioning this classical view of the Aegean extension. In this study, we wish to constrain the potential activity of dextral strike slip faulting during Mid-Miocene in Continental Greece.

Geological Setting Central Greece is characterized by the stacking of two units, from bottom to top: 1/ the Cycladic Unit made of HP rocks so-called the Cycladic Blueschist Unit (C.B.U) and 2/ the Pelagonian unit made of metasediment covered by Trias-Jurassic marble and limestone. The boundary between these two terranes is characterized by the N50 Pelagonian fault (Xypolias et al., 2003). In order to constrain the potential mid-Miocene activity of N50 dextral faults and achieve our objective, we focus on Evvia, Attic and, Continental Greece, to understand the tectonic context of the deposition of two mid-Miocene basins 1/ in the south of Evvia and Attic which border the N50 Pelagonian fault and 2/ in the north of Evvia far from N50 structures. We complete field data with Apatite Fission track currently non-existent in the area.

Geological Data The Northern Miocene basin shows N150 normal faults and late E-W normal faults. The major N150 faults are systematically associated with larger amount of sedimentation indicating syn-kinematical filling of the basin. This suggests N150 faulting during mid Miocene. Field arguments do not allow us to know the chronology of the appearance and activities of the E-W faults. However, they have the same orientations and characteristics as the normal faults bordering the Gulf of Corinth as well as the faults mapped by (Royden and Papanikolaou, 2011). These faults are therefore supposed to have been active since the Pliocene and are younger than the N150 faults. The Southern Miocene basin is located near the roughly N50 Pelagonia fault between the Cycladic Blueschist Unit and the Pelagonian unit. The entire Mid-Miocene basin is located on Pelagonian rocks. It is bounded to the south by the Pelagonian fault and does not extend beyond it. This particular geometry shows an overlap of this basin by the fault that delimits it and indicates that it predates the functioning of the fault. However, the bedding in the basin are sub-horizontal, even close the fault, suggesting a deposition after the fault activity. Faults and folds analysis demonstrates the existence of a major dextral slip kinematic associated with this N50 fault. All these data allow us to argue for a dextral strike slip activity of the Pelagonian fault during mid Miocene time.

Apatite Fission Track Data Times Samples for the apatite fission track (AFT) method were collected along a cross line perpendicular to the Pelagonian fault and along the N150 and N-E faults. This sampling logic aims to better constrain the large-scale deformation associated with the formation of the Miocene basin and to indirectly date the activity of the Pelagonian fault by comparing the Cycladic and Pelagonian AFT ages (AFT data in the Cyclades from Hejl et al., 2008, 2003; Ring et al., 2007). The study of AFT averages reveals a first tectonic event during the Oligocene to early Miocene. This one stands out on the majority of the rocks imposing an event impacting the whole of Continental Greece important. Two sample (G11-G16) show younger mean age with a last stage of exhumation in the middle Miocene. These two samples are located on the hanging-wall of the N150 fault, allowing a dating of the activity of these faults at mid-Miocene time, an interpretation that is consistent with the findings from the basin analysis. These new data in Continental Greece highlight a major change in age distribution between the C.B.U. rocks exhumed during the Mio-Pliocene and the Oligo-Miocene Pelagonian rocks. This difference is attributed to a recent exhumation event affecting only the Cyclades at the end of the Miocene. From these results, we can hypothetise that the N50 Pelagonian fault was active since the mid-Miocene, as a major strike slip fault that potentially accommodate strain partitioning during back arc extension.

Discussion This study provides new field and dating data allowing a better understanding of the evolution of Continental Greece since the Oligocene. It could be describe in three steps: • A generalized extension over the entire Aegean domain in the Eo-Oligocene period, creating a first episode of slow exhumation of deep rocks followed by the formation of metamorphic Core Complex. • A change in back-arc extension at mid Miocene time, implying the coeval activity of N50 dextral strike slip and N150 normal faults. • A second change in back arc dynamics at 5Ma with the interplay between NAF and back arc extension and the formation of the Corinth and Evvia rifts system with E-W normal faults. The origin of such strain partitioning during mid-Miocene time between N150 extensional fault and N50 dextral strike slip is most probably the interplay between the extension related to the retreat of the slab and the onset at around 15 Ma of westward extrusion of Anatolia.

References Armijo, R., Meyer, B., Hubert, A., Barka, A., 1999. Westward propagation of the North Anatolian fault into the northern Aegean: Timing and kinematics. Geology 27, 267. https://doi.org/10.1130/0091-7613(1999)027<0267:WPOTNA>2.3.CO;2 Hejl, E., de Grave, J., Riedl, H., Weingartner, H., Van den haute, P., 2008. Fission-track thermochronology of the Middle Aegean Island Bridge – implications for Neogene geomorphology and palaeogeography [Spaltspuren-Thermochronologie der Mittelägäischen Inselbrücke – ein Beitrag zur Kenntnis der geomorphologischen und paläogeografi schen Entwicklung während des Neogens.]. Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 159, 495–512. https://doi.org/10.1127/1860-1804/2008/0159-0495 Hejl, E., Sekyra, G., Friedl, G., 2003. Fission-track dating of the south-eastern Bohemian massif (Waldviertel, Austria): thermochronology and long-term erosion. International Journal of Earth Sciences 92, 677–690. https://doi.org/10.1007/s00531-003-0342-y Hubert-Ferrari, A., Armijo, R., King, G., Meyer, B., Barka, A., 2002. Morphology, displacement, and slip rates along the North Anatolian Fault, Turkey: THE NORTH ANATOLIAN FAULT. Journal of Geophysical Research: Solid Earth 107, ETG 9-1-ETG 9-33. https://doi.org/10.1029/2001JB000393 Kokkalas, S., Aydin, A., 2013. Is there a link between faulting and magmatism in the south-central Aegean Sea? Geological Magazine 150, 193–224. https://doi.org/10.1017/S0016756812000453 Ring, U., Glodny, J., Will, T., Thomson, S., 2007. An Oligocene extrusion wedge of blueschist-facies nappes on Evia, Aegean Sea, Greece: implications for the early exhumation of high-pressure rocks. Journal of the Geological Society 164, 637–652. https://doi.org/10.1144/0016-76492006-041 Royden, L.H., Papanikolaou, D.J., 2011. Slab segmentation and late Cenozoic disruption of the Hellenic arc: DISRUPTION OF THE HELLENIC ARC. Geochemistry, Geophysics, Geosystems 12, n/a-n/a. https://doi.org/10.1029/2010GC003280 Xypolias, P., Kokkalas, S., Skourlis, K., 2003. Upward extrusion and subsequent transpression as a possible mechanism for the exhumation of HP/LT rocks in Evia Island (Aegean Sea, Greece). Journal of Geodynamics 35, 303–332. https://doi.org/10.1016/S0264-3707(02)00131-X

ABSTRACT. Crete lies close to the convergence boundary of African and Euro-Asiatic continents and consists of a series imbricate tectonic units (nappes), which consist of Alpine formations (Creuzburg and Seidel 1975, Bonneau 1976,). These formations were formed in different palaeo environments but each unit has its own deformational and metamorphic history. Except these sediments there occur post-alpine sediments where the Neogene sediments dominate. The nowadays configuration of Crete is the result of several tectonic processes. The main processes are: a) A compressional tectonic phase which accumulated the tectonic nappes and caused the metamorphism of some units under HP/LT conditions in Oligocene (Seidel et al., 1982), b) The consequent fragmentation of the emergent areas due to the extension, which caused the formation of trenches and horsts and the deposition of Neogene sediments. (Meulenkamp et al. 1994). c)The post-Miocene warping of the crust, which led to the exhumation of metamorphic complex of Crete and the formation of detachment faults. (Fassoulas et al., 1994).

ABSTRACT. The outer part of the Hellenic arc undergoes a late-orogenic extension since the Miocene, which was installed in an area that had initially undergone the stacking of a number of thrust nappes. This build-up was the direct result of the orogenic process caused by the subduction of the African plate to the south beneath the Eurasian plate in the north, which culminated in the Upper Tertiary, simultaneously eliminating a large number of paleogeographical domains that were part of the Tethys' ocean. This late-orogenic extension was expressed: a) by the exhumation of the deepest tectonic units metamorphosed in low-grade conditions in the Upper Oligocene - Lower Miocene, constituting the footwall of low-angle normal faults (detachment faults) and building up the core of the large tectonic windows in the high mountain ranges of Crete and the Peloponnese; b) the creation of tectonic post-alpine basins defined by high-angle normal faults and filled by syn-rift sediments of Upper Miocene-Quaternary age. This paper describes an intra-mountainous high-to moderate-angle normal fault system that constitutes the eastern margin of the tectonic window of Mt Parnon in the eastern Peloponnese. It is a significant tectonic structure which is at the same time a) the main eastern marginal fault of the metamorphic rocks of the deepest Plattenkalk Unit and b) the morphological boundary between the high topographic area of the mountain range and the lower hills of the Kynouria sector. With a length of 35 km striking NW-SE and having NE dips, it consists of four segments separated by lateral NE-SW high-angle normal faults that have cut the northern part of the metamorphic core. Its central segment, the Platanaki fault, controls an impressive slope of about 500m height (Fig. 1). This fault system is the last expression of the late-orogenic extension that affected the area, overprinting the earlier detachment faults formed in the Middle Miocene-Lower Pliocene. Although an intra-mountainous one it must be regarded as contemporary with those faults that control the western margin of Mt Parnon that led to the final exhumation of the marbles of Plattenkalk Unit on the earth surface and its elevation at altitudes >1800m, feeding material to the Upper Pliocene-Quaternary basins of the southern Peloponnese.

ABSTRACT. The NW–SE trending fault-bounded Axios, Mygdonia, Strymon and Drama basins dominate the Central and Eastern Macedonia landscape and geological structure (Mercier et al. 1989, Mountrakis et al., 2006, Tranos 2011). They were formed during the Late Miocene to Pliocene NE–SW directed extensional stresses, which primarily activated NW–SE striking normal faults. Since the Quaternary the stress field has changed and is now dominated by N-S extension, resulting to the formation of E-W trending normal faults, reshaping the pre-existing basins (e.g. Lyberis 1984, Pavlides & Kilias 1987). Isoseismal data from past earthquakes indicate that both the NW-SE faults (e.g. 1902 M=6.6 Assiros and 1932 M=7.0 Ierrisos earthquakes) and the E-W trending faults (e.g. 1932 M=6.2 Sochos and 1978 M=6.5 Volvi earthquakes) are active (Papazachos et al., 1979, Voidomatis et al., 1990). Limited paleoseismic investigations have been carried out along some of the E-W oriented fault zones in northern Greece (e.g. Chatzipetros et al., 2005), yet none have previously applied on the NW-SE oriented fault zones in this region. 4 paleoseismic studies were carried out to assess the location, geometry, kinematics, and past surface displacements of the NW-SE trending Symvoli-Fotolivos (SFFZ – Drama Basin), Tholos-Nea Zichni fault zone (TNFZ – Strymon Basin), Assiros Krithia fault (ASFZ – Mygdonia Basin) and Drymos fault zone (DRFZ – Mygdonia Basin) (Figure 1). Methodology The largest paleoseismic study has been performed in Northern Greece in order to assess whether NW-SE trending basin bounding faults are Holocene active with important implications in seismic hazard assessment. Kinematics and past surface displacements associated with these fault traces were assessed by detailed geomorphological, geological and paleoseismic trench investigations. For the SFFZ a 221 m long and 3 m deep trench was excavated, while for the TNFZ the trench was 153 m long and 1.5 - 3 m deep. Paleoseismic observations for ASFZ and DRFZ were performed along targeted sections of an existing 3 m deep, two-side sloped construction trench. All trenches were cleaned, gridded, photographed, georeferenced and logged. Samples also were collected for radiocarbon dating where evidence for active faulting was found. Results & Discussion The SFFZ has a segment length of 32 km and yields an average magnitude value of Mw=6.61. 2 events are inferred with vertical displacements of 66 cm (penultimate event ~11350±40 BP) and 75 cm (most recent event ~5620 ± 30 BP) implying an approximate 0.12 mm/yr throw-rate and 0.14 mm/yr slip-rate, respectively (Figure 2). Geological and geomorphological data for TNFZ strongly support a 15 km long fault segment, which represents the preferred rupture scenario. Radiometric dating provides limiting ages of surface displacements along a synthetic fault plane about 4950 ± 30 years ago, and along an antithetic fault plane about 2840 ± 30 to 6300 ± 30 years ago. As a result, 1 or 2 events appear to have occurred along this fault in the past 6300 years, implying slip-rate of 0.20 ± 0.1 mm/yr, with recurrence intervals of ~3000 yrs (Figure 3). Holocene deformation occurred along both the ASFZ and DRFZ. 2 events have occurred in ASFZ, around 4540 and 7900 years BP. The total displacement over the last 7900 years is 121 cm, implying a 0.15 mm/yr slip-rate, with a recurrence interval of 3360 yrs. The DRFZ is an 8 to 10 km long structure with a slip-rate on the order of 0.1-0.3 mm/yr. The fault could produce average displacements of 13 to 28 cm and maximum displacements of 24 cm to 40 cm. We interpreted 3 possible paleo-events with vertical displacements exceeding 40 cm, implying a possible multi-segment rupture scenario involvinh the Gerakarou-Liti fault zone, which is parallel to DRFZ with a step over of only 2 km. The DRFZ is characterized by distributed deformation with 8 major and secondary fault planes observed at four different sites (T1-T4) across the trench. Dating results confirm that 4 of these fault planes have produced displacements between approximately 4000 and 9000 ybp (Figure 4).

ABSTRACT. The present‐day tectonic stress pattern in Northern Greece has been active since Pleistocene, showing a slightly radial crustal extension with variable trend (N-S to NNW-SSW) in central Macedonia. The fault pattern is almost perpendicular to the stress field, crosscutting the older NW-SE alpine deformation structures (Sboras et al., 2017). The current active stress field in the broader area of Thessaloniki has its extensional axis directed N-S, while the corresponding active faults are generallyE-W trending. In the past couple of decades, GNSS measurements are widely used as a well‐established tool in earth crustal deformation studies. The synergy between geodesy and geophysics can provide some very promising discussions about the Earth's upper crustal processes (Lazos et al., 2018). In this paper the extension of Athemous fault zone at the broader Thessaloniki area is examined, using an integrated geodetic and geomorphologic approach. The largest part of the study area is covered by Quaternary deposits, which were developed at the northern side of Anthemous river basin and the basins of Gallikos, Axios, Loudias and Aliakmon rivers (Thessaloniki plain). The deposits are mainly fluvial - torrential sediments containing marsh – marine or fluvial – deltaic layers. The Neogene Sandstone – Marl formation Series underlies the Quaternary sediments. This series consists of layers of very dense sand and sandstone, alternating with clay and silt of light brown to light green color. This formation covers a large part of the broader area. In the study area, this series is extended along the main fault zone from Galarinos to the East, up to the west shoreline of Thermaikos Gulf at the area of Aiginio and Melini. This series is in tectonic contact with the Quaternary deposits of Anthemous basin and the Thessaloniki plain sediments. The oldest Neogene Red Clay Series outcrops at the eastern part of the fault zone. This series consists of alternations of red color very stiff clays, sand and gravel layers and lenses. The largest active fault zone in the immediate vicinity of Thessaloniki metropolitan area, is the Anthemus normal fault zone, which is located ca. 15 km to the south (F-An). The general strike of the zone is E-W, dipping to the north, while its total mappedt length is ca. 32 km. It can be divided into three discrete segments, namely the Galarinos - Neo Risio, the Aggelochori area (Zervopoulou, 2010) and a possible third one, which is considered to be an extension to Thermaikos Gulf, detected from geophysical (seismic) investigations (Chronis, 1986). In this paper, the existence of a probable fourth segment in Aiginio area is also discussed. The activity of this fault zone is inferred by several indications. It defines the contact between the Neotegene series at the south and the Holocene sediments at the central and north part of the basin. The application of quantitative geomorphic indices shows that the relief is responding to a relatively recent activity, as documented by various factors. The dissimilar development of the tributary network between the north and the south banks of Anthemous River, shows a tilting to the south along the surface fault trace. In addition, the asymmetry index of the basin, as well as the poor water channel development at the south part of the basin, indicate that the area has been subjected to rather recent deformation. Mountain front sinuosity is low, also suggesting a relatively high uplift rate of the footwall. The Aggelochori area segment shows indications of higher activity, as is suggested by steep slopes (cliffs). Some other indirect signs of neotectonic activity are the existence of hot springs in the Souroti area, with travertine deposits aligned along the fault line (Zervopoulou & Pavlides, 2005). This fault is also probably associated to the M 6.2 earthquake of Vasilika , as well as with aseismic creep along the fault line at Peraia area. The aseismic cracks follow the fault trace, however they have been attributed to overpumping. The western extension of Anthemous fault zone towards Aiginio area is a research objective that has not yet been confidently resolved. To this end, a geodetic approach has been applied by extrapolating the active geodynamic state of the area by using primary geodetic data. They have been recorded for seven years (2008-2014) by 18 permanent GPS/GNSS stations in the broader area. Data were recorded daily in 30-second increments. The reference frame of these data is ETRF2000, which assumes that Eurasia is stable. The data processing involved GPS triangulation of three different GPS/GNSS stations, based on the vector analysis of East and North velocity components and their uncertainties. Any given three stations form a triangle, while each of them is located on a triangle vertex., The triangle centroid is determined by taking into consideration the intersection of the triangle medians and the inner circle of the triangle is inscribed. Then, the triangle vertices (GPS/GNSS stations) are relocated, based on their recorded velocity vectors, leading to the deformation of the inner circle into an ellipse. The combination of the major and minor axes of the inner circle and the ellipse, respectively, using specific equations, results in the calculation of certain parameters related to the active deformation of the area (e.g. Lazos et al., 2018). The combination of these 18 GPS/GNSS stations of the broader area led to the construction of 348 different triangles (http://www.unavco.org/). The maximum horizontal extension is one of the parameters that is directly associated with the determination of the tectonic regime of a study area (extensional or compressional). The calculated maximum horizontal extension values, as well as their geostatistical process (interpolation), confirm that the probable western Anthemous fault zone prolongation is characterized by the highest values of the study area (approximately 200-230 nano-strain), Figure 1. In addition, high values are observed at the eastern part of Thessaloniki city, where numerous faults have been mapped. These high maximum horizontal extension values however, cannot be attributed to a specific fault, as they are concentrated within a limited area. While geodetic analysis shows that there is a considerable active deformation at the westward probable extension of Anthemous fault zone towards Aiginio area, the continuation cannot be verified due to the lack of precise offshore information. Nevertheless, a geomorphological assessment of Aiginio area shows that there are ESE-WNW to E-W trending linear features that are in good agreement with the expected fault pattern (Figure 2). They form a low relief with no significant linear scarps, indicating thus that this probable segment is of lower activity level. Further research is needed in the area in order to establish a reliable correlation between the different fault strands.

ABSTRACT. The island of Crete is located at the southern part of the Hellenic Arc, where active extension occurs at the overriding plate of the Africa – Eurasia retreating subduction. Onshore and offshore faults in Crete display significant morphological features formed by the Pleistocene to present extensional activity, while their strike is both arc-parallel and arc-normal (Angelier, 1979; Armijo et al., 1992).

The study area is located in the eastern Mirabello bay, Lasithi District, where Late Quaternary normal faults NNE-SSW to NE-SW trending are exposed around Mirabello bay. The most significant fault structure is the Ierapetra Fault Zone (IFZ), a NNE-SSW normal fault zone that extends from the northern to the southern coast of Crete (Fortuin, 1978; Fytrolakis & Dermitzakis 1996, Caputo et al., 2010). IFZ consists of multiple normal fault segments, parallel and overlapping. The main IFZ is divided (from north to south) into Kavousi segment, Ha Gorge and Vainia segments, while Lastros and Sfaka faults are encountered to the east, along IFZ footwall (Caputo et al., 2006, Gaki-Papanastassiou et al., 2009, Mason et al., 2016, Veliz et al., 2018). A second, less well defined, fault zone is developed along the coast of eastern Mirabello bay; Pachia Ammos coastal fault and Psira offshore fault to the north. These faults are parallel to the IFZ and follow the eastern coast and bathymetric relief.

Figure 1. A) Late Quaternary faults in the area of study (eastern Mirabello bay, Ierapetra, Crete). B) Detailed fault traces mapped in the Tholos site. C) Profile of the main normal fault in Tholos site, with Late Quaternary colluvial sediments deformed and rotated on the hangingwall. D) View of the fault scarp in the southern Tholos site, with part of the footwall removed from a paleo-landslide.

In this study, we examine in detail a section of the Pachia Ammos fault zone. The site is located at the northernmost tip of the steep coast of east Mirabello bay, near Tholos site (Figure 1). Footwall lithology is comprised by carbonate Alpine rocks, mainly dolomites and dolomitic limestones of Triassic age (Papastamatiou et al. 1959). Different generations of Quaternary debris and colluvial terrestrial sediment scree can be found along the fault scarps and on the western slopes of the site. The morphology is dominated by the steep bedrock scarps formed by normal faulting or landslide erosion. Coastal erosion and a large paleo-landslide at the southern part of the site have removed part of the colluvial sediments and the fault scarp (Figure 1C-D). Fault traces were mapped in a 1:2000 scale (Figure 1B) and reveal a composite fault structure with parallel fault scarps, and fault setbacks showing a variation in fault strike from west to east. The change in the fault strike from NNE-SSW to NE-SW occurs at the northern edge of the Pachia Ammos footwall and we examine two different scenarios to interpret this change of geometry: • related to the development of a brecciated relay ramp between the Pachia Ammos fault and the Kavousi fault. • different geometry and probable left-stepping overlap between Pachia Ammos and Psira faults. Adjacent to the faults, deformed outcrops of the fault zones reveal deformed and tilted late Quaternary terrestrial deposits, a clear indication of recent fault activity. Although there is a lack of detailed offshore surveys in the area, we interpret the Pachia Ammos and Psira footwalls as part of a series of backtilted fault blocks towards the IFZ. Although the coastal/offshore faults of Pachia Ammos and Psira preserve a lower morphological imprint due to coastal erosion and submergence of the hanging-wall than the IFZ, their structural features, geometry and segmentation contributes to the better understanding of the active extension in the eastern Mirabello bay. We conclude that paleoseismological and displacement features and observations is crucial for the further improvement our current understanding on the seismic hazard assessment of a rapidly developing area and a popular tourist destination..

References Angelier, J., 1979. Neotectonique de l’Arc Egeen, Soc. Geol. Du Nord, 3, 418. Armijo, R., Lyon-Caen, H., Papanastassiou, D., 1992. East-west extension and Holocene normal-faults scarps in the Hellenic arc, Geology, 20, 491–494. Caputo, R., Monaco, C., Tortorici, L., 2006. Multiseismic cycle deformation rates from Holocene normal fault scarps on Crete (Greece). Terra. Nova 18, 181–190. Caputo, R., Catalano, S., Monaco, C., Romagnoli, R., Tortorici, G., Tortorici, L., 2010. Active faulting on the island of Crete (Greece). Geophys. J. Int. 183, 111–126. Fortuin, A.R., 1978. Late Cenozoic History of Eastern Crete and implications for the geology and geodynamics of the southern Aegean Area. Geologie en Mijnbouw 57(3), 451-464. Fytrolakis, N., Dermitzakis, M., 1996. Map of Active Faults of the area of Crete Island. Earthquake Protection and Planning Organization, Athens. Gaki-Papanastassiou, K., Karymbalis, E., Papanastassiou, D., Maroukian, H., 2009. Quaternary marine terraces as indicators of neotectonic activity of the Ierapetra normal fault SE Crete (Greece). Geomorphology 104, 38–46. Mason, J., Schneiderwind, S., Pallikarakis, A., Wiatr, T., Mechernich, S., Papanikolaou, I., Reicherter, K., 2016. Fault structure and deformation rates at the Lastros-Sfaka Graben, Crete. Tectonophysics 683, 216–232. Papastamatiou, I., Vetoulis, D., Tataris, A., Bornovas, I., Christodoulou, G., Katsikatsos, G., 1959. Geological Map of Greece in 1:50000 scale. Map Sheet Ierapetra – Kato Chorion. IGME, Athens. Veliz, V., Mouslopoulou, V., Nicol, A., Fassoulas, Ch., Begg, J., Oncken, O., 2018. Millennial to million year normal-fault interactions in the forearc of a subduction margin, Crete, Greece. Journal of Structural Geology 113, 225-241.

ABSTRACT. Determining the absolute age of the past faulting activity is crucial for assessing seismic hazards in a particular area. Historical records can be used for such purposes, however they only provide a relatively recent picture of fault activity, which is generally inadequate for drawing concrete conclusions on the seismicity of an area. As such, geochronology approaches try to address this problem using appropriate dating techniques on earthquake-disturbed materials prior to the time of recorded information. The employment of the luminescence dating techniques is now widely applied to variety of materials and sedimentary environments (e.g., quartz and feldspar from heated archaeological material, sand-dunes and fluvial sediments), their application however on fault-deformed materials still limited, since full resetting (due to mechanical crushing/sliding or frictional heat) of their luminescence signal, during a rupture event, cannot be easily established (e.g., Toyoda et al., 2000), but also due to the limited access to appropriate material (e.g., fault gouges; crushed and ground-up rock produced by friction between the two sides when a fault moves). No systematic effort has been made up to now on the use of luminescence in directly dating material from the brittle zone of a fault which is related to faulting or the earthquake event. To this end, the current study explore the use of both Isothermal Thermoluminescence (ITL) and Optically Stimulated Luminescence (OSL) to date past seismic deformed features which are directly linked to past seismic events and develop detailed protocols and methodological approaches on the use of the two techniques, so that the long-term temporal behavior of seismically active faults could be realistically evaluated and modeled. This work is part of a feasibility study using fault gouge and breccia material acquired from a drilled core of the Nojima Fault Zone, as well from an exposed outcrop of the Asano Fault, which belong in one of the most active fault systems in southwest Japan (Research Group For Active Faults of Japan, 1991). Our approach is based on an enhanced chronological model which builds on the earlier set of luminescence ages on quartz and feldspar produced by Tsakalos et al. (2018). Microstructural observations on the Nojima Fault core revealed that the fault gouge zone is made of thin layers (mm to cm) of different colour, with each layers most probably corresponding at least to one seismic slip event (Lin and Nishiwaki, 2019). Thus, to assess the age of the gouge layers, we tried to sample each one individually. As for the Asano Fault, sampling was achieved by hammering steel cylinders in an exposed gouge formation. In the case of Asano, gouge layering was not very clear and thus collected sub-samples most probably contained several gouge layers. Intercalated breccia samples were also collected from both faults. The Single-Aliquot-Regenerative-dose (SAR) approach (Table 1 and 2) was employed for both ITL (Choi et al., 2006) and OSL (Murray and Wintle 2003) measurements on quartz and feldspar. Table 1. The SAR-OSL protocol applied to quartz grains. Step Treatment 1 Give dose 2 Preheat, 10 s at 240 ˚C 3 Blue-LED stimulation, 40 s at 125 ˚C 4 Give test dose 5 Cut-heat, 0 s at 200 ˚C 6 Blue-LED stimulation, 40 s at 125 ˚C 7 IR diodes stimulation, 100 s at 125 °C 8 Return to Step 1

Table 2. The SAR-ITL measurement protocol applied to quartz and feldspar grains. Step Treatment 1 Give dose, Di(a) 2 Heat to 310°C, (hold for 300 s) 3 Give test dose, Dt (b) 4 Heat to 310°C, (hold for 300 s) 5 Return to step 1

(a) D0 = natural dose; (b) Dt= Fixed test dose Typical examples of decay and growth curves of the ITL and OSL signals appear in Fig. 1. Their natural dose and their dose response curves are well described by fitting of a saturating exponential function.

Fig. 1. Representative dose response curves and luminescence decay curves for the ITL and OSL signal measured in a) feldspar and b) quarts grain aliquots. Lx/Tx is the corrected luminescence signal for the equivalent radiation dose (DE).

Luminescence dating results on fault gouge revealed that both techniques could produce reliable results giving very similar ages on the same samples and indicating a continuing activity of the two faults during the Middle-Upper Pleistocene. However, ITL ages were slightly older than the OSL ages, most probably suggesting partial resetting of the ITL signal. It should also be stressed here that, some mixing of the different gouge layers during sub-sampling might be apparent and thus gouge ages may represent a mixture of fault raptures. On the other hand, observations of the OSL and ITL signals of breccia samples appear unusual, not following the expected signal decay behaviour and thus they were excluded from further analysis. This study is a fundamental advancement in the field of palaeoseismology, as it provides evidence of the potential of the luminescence dating techniques to be used for assessing the neotectonic activity of an area while its methodological approach could become a principal part for geo-hazards evaluations.

Acknowledgments This research project was supported by the Secretariat of the Nuclear Regulation Authority of Japan and partially by JSPS KAKENHI Grant Number JP18H01309. Part of this study has also received funding from the State Scholarships Foundation (IKY) co-financed by the European Union (European Social Fund-ESF) and Greek national funds through the action entitled “Reinforcement of Postdoctoral Researchers”.

References Choi, J.H., Murray, A.S., Cheong C.S., Hong D.G., Chang, H.W., 2006. Estimation of equivalent dose using quartz isothermal TL and the SAR procedure. Quaternary Geochronology, 1, 101-108. Lin, A., Nishiwaki, T., 2019. Repeated seismic slipping events recorded in a fault gouge zone: evidence from the Nojima Fault drill holes, SW Japan. Geophysical Research Letters, 46, https://doi.org/10.1029/2019GL081927. Murray, A.S., Wintle, A.G., 2000. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements, 32, 57-73. Research Group for Active Faults of Japan., 1991. Active Faults in Japan-Sheet Maps and Inventories (revised edition). University Tokyo Press, Tokyo, Japan 437. (in Japanese with English summary). Toyoda, S., Rink J., Schwarcz P., Rees-Jones J., 2000. Crushing effects on TL and OSL on quartz: Relevance to fault dating, Radiation Measurements 32, 667-672. Tsakalos E., Kazantzaki M., Lin A., Nishiwaki T., 2018. Luminescence and ESR dating of fault gouge materials from the Nojima fault - Japan. American Geophysical Union (AGU Fall Meeting 2018), December 10-14, Washington, Maryland, USA.

ABSTRACT. The advances of GPS technology, such as the expansion of dense GPS networks with high sampling rate (even up to 10Hz), and the broader development of other satellite systems (GLONASS, BeiDou, etc.) have made GNSS an important tool in deformation monitoring applications in geohazards and potentially in early warning systems. Recent studies have shown the potential contribution of GPS in estimating earthquakes characteristics (magnitude, PGV, etc.). However, most of them are based on the analysis of the GPS coordinate time series aiming to determine the characteristics of the deformation and relate them to the current phenomenon. A recent approach has been developed, which is based on the analysis of GPS network data using temporal and spatial analysis algorithm for the detection anomalies potentially related to geohazards. The application of artificial neural networks and the spatial regression model are adopted to detect changes through the analysis of the time-history of the GPS records and their spatial correlation. Through their application in different case studies, it is shown that the temporal analysis is more effective for rapid, short-period changes, while the spatial analysis is more suitable for slowly developed anomalies.

ABSTRACT. The Geohazards Lab is an initiative developed within the framework of the Committee on Earth Observation Satellites (CEOS) Working Group on Disasters (WG Disasters) to enable a greater use of Earth Observation (EO) data and derived products to assess geohazards and their impact. The aim is to establish an inclusive and comprehensive process to optimize the use of EO technologies starting from the needs of national and local decision-makers in political and socio-economic sectors relevant to Disaster Risk Management (DRM). The Geohazards Lab is based on a group of interoperable platforms with federated resources to animate and support the geohazards user community. It is originated by the European Space Agency (ESA), with the support of several other CEOS space agencies and partners, including the Italian Space Agency (ASI), the French Space Agency (CNES) and the German Space Research Centre (DLR), as well as several research institutes including BRGM, INGV, CNR-IREA, CNRS-EOST, NOA, NORUT and IGME. Based on the success demonstrated during the CEOS Seismic Hazards Pilot activity, the Geohazards Exploitation Platform (GEP, geohazards-tep.eo.esa.int) continues to contribute in the CEOS Geohazards Lab initiative. The GEP is an activity originated by ESA in November 2015 and led by Terradue, to support the geohazards community exploiting satellite EO data to assess geohazard risks. It provides a data delivery mechanism, on-line processing tools and services and an e-collaboration environment to exploit EO data to assess geohazards and their impact. Conventional InSAR services (e.g. DIAPASON and SNAP S-1 DInSAR service), advanced InSAR services (e.g. InSAR SBAS of CNR-IREA), optical on-demand services (e.g. MPIC OPT, ALADIM and DSM OPT of the University of Strasbourg/CNRS EOST) and optical systematic services (e.g. INGV’s STEMP for surface temperature mapping, NOVELTIS and INGV’s VEGAN services for hot spot and vegetation vigor mapping) have been made available or are currently under integration. New platform functionalities are under implementation, such as the alerting system for automatic deformation mapping that shall trigger the services available on GEP based on seismic events polled from external systems e.g. the EMSC, USGS pager and Copernicus EMS. The Geohazards Lab envisages building a collaborative framework with expert geoscience centres and users to achieve a greater adoption of EO methods. Its goals are to support the exploitation of online hosted processing capabilities with a focus on cloud processing solutions, define consensus methods in liaison with experts to harmonize EO based products and establish a methodological approach to support the generation of reference ground deformation measurements in support to historical hazard analysis. Focusing on the harmonization of EO based products, the Geohazards Lab intends to coordinate with other available capabilities such as for instance the European Plate Observing System (EPOS), the Norwegian Ground Motion Service (NGMS), the Supra National Ground Motion Service (SNGMS) and the Geohazards Office (initiated by BRGM) to support a scientific animation activity and to work on common guidelines for standards and formats of EO based terrain motion measurements. The Geohazards Lab supports users with EO expertise from geoscience centres who are the priority intermediaries with end users from local and regional DRM organisations. Users from both the EO and non-EO community can benefit from this effort as it will facilitate (i) the broader use EO products sharing common standards by EO practitioners, (ii) the interoperability of results obtained by different data provides within or outside EO processing platforms and (iii) an easier end-product interpretation by decision makers.

ABSTRACT. Since 2015 ESA provides early access to an on-line processing platform for satellite data, the Geohazards Exploitation platform or GEP https://geohazards-tep.eu/ GEP aims to support the exploitation of satellite EO for geohazards. It follows the Supersites Exploitation Platform (SSEP), originally initiated in the context of the Geohazard Supersites & Natural Laboratories initiative (GSNL). The Geohazards platform has been expanded to address broader objectives of the geohazards community. In particular it is a contribution to the CEOS Working Group - Disasters to support its Seismic Hazards Pilot and terrain deformation applications of its Landslide & Volcano Pilots. GEP is sourced with elements – data, tools, and processing including INSAR – relevant to the Geohazards theme and related exploitation scenarios. It offers the following advantages: a) Rapid on-demand production as soon as satellite data are available (within few hours up to a few days) b) Semi-automatic production: the user can manipulate certain parameters, versatility in date and frame selections and c) Does not require advanced knowledge of methodologies from the user perspective, but enables a greater choice of products than pure automatic pipelines. The Geohazards TEP product analysis permits the user to obtain results on: a) Primary surface faulting and deformation, b) Earthquake Environmental Effects (sec. faulting, triggered ruptures, landslides), c) Coherence shadows and multi-temporal coherence evaluation and d) Line-of-Sight (LOS) displacement (InSAR data) and 2D horizontal displacement (Optical data).

Geohazards TEP provides an effective platform to study earthquakes using InSAR & optical analysis. The Sentinel-1 and GEP tools (SNAP, DIAPASON, GMTSAR, MPIC-OPT etc.) captured surface deformation due to many strong events during 2018, with a threshold as low as MW 4.9 (Catania, Italy Dec 26 2018). The semi-automatic nature of GEP platform is extremely useful to a Geoscientist End-User, with versatility in parameters and product selection. It was also demonstrated that optical displacement data (Sentinel-2/MPIC-OPT) are not an alternative to SAR geodesy, but have a complimentary role, for better capturing near-fault displacement than InSAR.

We examine the most significant shallow earthquake events between December 2017 and December 2018 (Fig. 1). The GEP tools and Sentinel1/2 imagery products are used to identify and examine earthquake surface ruptures, co-seismic landslides and other earthquake environmental effects. The majority of moderate/strong shallow events were identified in Sentinel-1 InSAR products and examples are presented for each single event or earthquake sequence (Fig. 2). Using GEP we identified coseismic deformation of moderate-magnitude events like Perth, Australia and Catania, Italy (Valkaniotis 2018), strong earthquake sequences with multiple events like Lombok, Indonesia (Ganas et al. 2018), as well as in large plate boundary events such as the MW 7.5 Palu, Indonesia earthquake (Valkaniotis et al. 2018). In addition, optical image correlation from Sentinel-2 imagery through the MPIC-OPT service (Stumpf et al. 2017) assisted in measuring near-fault large displacements, where InSAR is difficult to be applied due to lack of correlation and lack of coherence.

ABSTRACT. We present preliminary analysis of the fault model and the shallow earthquake sequence offshore Zakynthos (Ionian Sea, Greece) that was initiated by the October 25, 2018 Mw(NOA)=6.7 earthquake . We use geodetic and seismological data (phase data and moment tensor solutions from NOA) to identify the geometry and kinematics of the fault plane using linear inversion techniques in elastic half-space. First, we analysed the time series of fourteen (14) permanent GNSS stations located around the epicentre, two of them (ZAKU, ZAKY) being located on the island of Zakynthos and one (STRF) on the small island of Strofades. The stations are equipped with dual-frequency geodetic receivers and belong to several networks such as NOANET (Ganas et al., 2008; 2013), HxGN SmartNet Greece, Uranus (Greece) and RING (INGV). The GNSS data are processed using the GIPSY 6.4 software. This software uses a Precise Point Positioning processing strategy (Zumberge et al., 1997). We found that cm-size co-seismic horizontal offsets were recorded by the continuous GPS stations operating at both Zakynthos and Strofades islands. Secondly, for the broader region of Zakynthos, 2335 earthquakes were relocated using phases from the NOA online catalogue for the period 23 October 2018 - 17 January 2019, applying the nonlinear location algorithm NonLinLoc (Lomax et al., 2000). Thirdly, we processed Sentinel-1 SAR (C-band) data. Despite the large magnitude of the mainshock (M6.7), the surface deformation in Zakynthos is not clearly visible with differential InSAR because of the offshore occurrence of the earthquake. In various co-seismic interferograms we see small co-seismic displacements within 1 fringe (28 mm). This small visible signal is not consistent with the slip-model predictions, based on the GPS inversion models . We attribute the “reduced” InSAR signal in tropospheric effects that mask most of onshore deformation. We then modelled the co-seismic displacements by assuming that the earthquake corresponds to a homogenous slip on a rectangular fault buried in a elastic half space, and we use the formalisms of Okada (1992). The best fitting fault has a centroid at 6.5 km depth which is shallower than most seismological estimates (for example, the 12-15 km of GEOSCOPE). The GPS inversion product indicates that the 25 October 2018 earthquake was due to the activation of one reverse fault with a total length of about 30 km (see green rectangle in Fig. 1), at depths 5-15 km. The fault-dip direction is also retrievable from GNSS data inversion with a low-angle (25°), eastern-dip. Therefore, we propose that the M6.7 event occurred along a N-S striking seismic fault which is located on the African-Aegean plate interface (i.e. along the megathrust). As the October 25, 2018 event occurred along the Hellenic megathrust it signifies the high degree of seismic coupling in this region of the Hellenic Arc (i.e. Laigle et al., 2002). It also highlights the “strong” nature of the subducting slab with the occurrence of “locked” patches under the Ionian seafloor that fail during large, reverse-slip earthquakes. In addition, the data from the recent, strong seismic events of the western Hellenic arc (1976 Zakynthos, 1997 Strofades, 2018 Zakynthos) point to a sequence of a low-angle events along the plate interface with most of co-seismic deformation taken up by the upper (Aegean) plate (plate transport and uplift).

ABSTRACT. Rheticus® is an automatic cloud-based geoinformation service platform, designed to deliver fresh and accurate data and information for monitoring the evolution of the Earth's surface. The platform, provides information by means of graphic indicators, dynamic diagrams and pre-set reports. The provided information allow users to immediately perform assessment operations over areas of interest. Rheticus® Displacement represents a revolutionary model concept (through subscription) in monitoring critical infrastructure with the use of SAR data and the persistent scatter technique (PS), designed for users with high expectations in the value of information and its user friendliness provision. More specifically, Rheticus® Displacement provides accurate information to monitor over time, through Multi-Temporal SAR Interferometry (MTInSAR) analysis, movements occurring across landslide features or structural weaknesses that could affect buildings or infrastructures. Using European Copernicus Sentinel-1 (S1) open data images and MTInSAR techniques, the service is complementary to traditional survey methods, providing a long-term solution to slope instability and geohazards monitoring. The service update is guaranteed through the use of satellite images, mapping data and environmental information available online as open data. The service is updated with the availability of fresh incoming data, and the refresh rate can range from monthly to daily frequency depending on the service characteristics. Rheticus® Displacement is a turnkey vertical web service for the continuous monitoring via satellite of instability phenomena affecting transportation infrastructures (roadways, railways, including bridges and tunnels) and/or their nearby areas, caused by structural defeats or ground displacements such as landslides or subsidence phenomena. In this presentation, we focus on the great challenge of land and infrastructure monitoring as the key activity to ensure people’s safety, environmental protection and the safeguarding of assets at all stages of the life cycle of infrastructures, from design to production, management and maintenance.