THE GREEK CATALOGUE OF ACTIVE FAULTS AND DATABASE OF SEISMOGENIC SOURCES

The new reasearch project to create the Greek Catalogue of Active Faults and Database of Seismogenic Sources has three major goals: (i) the systematic collection of all available information concerning neotectonic, active and capable faults as well as broader seismogenic volumes within the Aegean Region; the search will be mainly based on geological and geophysical data; (ii) the quantification of the principal seismotectonic parameters of the different sources and the associated degree of uncertainty; (iii) to supply an integrated view of potentially damaging seismogenic sources for a better assessment of the Seismic Hazard of Greece. The informatic framework of the database follows that used for the Italian Database of Individual Seismogenic Sources (DISS). In this paper we present the architecture of the new Database of Active faults of the broader Aegean Area relative to Greece, the progress made up to present and the following activities yet to be accomplished

The geological structure of Kastas hill archaeological site, Amphipolis, eastern Macedonia, Greece

This paper presents research results on the geological structure of Kastas hill in Amphipolis, as well as the broader area. They consist of geological and geomorphological observations at Kastas and 133 hills and the surrounding areas, on their geological structure, the stratigraphy and the paleoenvironment. Kastas hill is the site of the largest burial mound discovered in Greece to date. The slopes of its embankment were recorded and modelled in detail using near field photogrammetry. The problem of distinguishing between in situ geological formations and ex situ anthropogenic deposits is also addressed. The bulk volume of Kastas hill consists of natural sediments; these sediments are exposed as successive alternating beds of grayish loose and cohesive sands with scattered pebbles and locally with cobbles. Clayey beds up to ~20-30 cm thick intercalate between the sands. At the top of the hill the anthropogenic deposits are typical of Macedonian tumuli, with soil and clay alternations for sealing and stabilizing them. Paleosoil horizons were observed both in natural sediments and within anthropogenic substrates. Two horizons were sampled for dating by different methods (OSL – optical stimulated luminescence and 14C – Accelerated Mass Spectroscopy). Their dating shows the development of successive deposits during the Iron, Archaic and Classical ages. The AMS dating of a charcoal which is closely associated to the construction of the main monument yielded an age of Cal. BP 2310 = Cal. 360 BC. 

KARST FEATURES AND RELATED SOCIAL PROCESSES IN THE REGION OF THE VIKOS GORGE AND TYMPHI MOUNTAIN (NORTHERN PINDOS NATIONAL PARK, GREECE)

Due to unfavourable natural conditions (poor soils, lack of water, special relief conditions), karst terrains have always been relatively sparsely populated, and they have been seriously affected by recent depopulation processes. However, the creation of national parks on karst terrains and the recent increase of (geo)tourism may influence and even turn these population trends. Our study examines the validity of this statement in the context of Vikos Gorge and Tymphi Mountain (NW Greece). Geological and geomorphological values are presented first, including Vikos Gorge, the glaciokarst landscape of Tymphi and the particular spherical rock concretions. Digital terrain analysis is used to obtain scientifically based, reliable morphometric parameters about Vikos Gorge, and it is found that the maximum gorge depth is 1144 m, the maximum width is 2420 m, and the maximum of depth/width ratio is 0.76. Thereafter, rural depopulation trends are examined and it is found that this region (Zagori) is seriously affected by depopulation. It is observed that there are differences among settlements, and a relative stabilization of population is sensible in only few settlements around Vikos Gorge, which are linked to tourism. As for nature protection, while at the beginning conflicts were perceptible among management and local people, now new conflicts are emerging between growing tourism and nature protection goals.Key words: gorge morphometry, glaciokarst, spherical concretions, rural depopulation, geotourism, national park.Kraške oblike in s krasom povezane družbene spremembe na območju soteske Vikos ter v gorovju Timfi (narodni park Severni Pindi, Grčija)Zaradi neugodnih naravnih razmer, kot so manj rodovitna prst, pomanjkanje vode in svojstvena oblikovanost površja, je kraško površje od nekdaj relativno redko poseljeno, v zadnjem obdobju pa je podvrženo tudi procesom odseljevanja. V zadnjem času je vse več tudi geoturizma in z njim povezanega ustanavljanja geoparkov, ki trend depopulacije lahko tudi obrnejo. Pričujoča študija se nanaša na vrednotenje omenjenih procesov na primeru doline Vikos in gorovja Timfi (SZ Grčija). Najprej so predstavljene geomorfološke in geološke značilnosti območja, kjer so izpostavljene značilnosti soteske Vikos, glaciokras gorovja Timfi in za to območje značilne okrogle skalne konkrecije. Digitalni model višin je bil namenjen morfometrični analizi soteske Vikos. Ta je pokazala, da je njena največja globina 1144 m, največja širina 2420 m, največje razmerje med globino in širino pa 0,76. V nadaljevanju so analizirane značilnosti odseljevanja s podeželja, katerim je najbolj podvrženo območje Zagori. Demografski vzorci kažejo na razlike med posameznimi naselji, kjer je število prebivalcev stabilno le v nekaterih naseljih v bližini turistično zanimive soteske Vikos. Z ustanovitvijo parka so se pojavili tudi konflikti. V začetku so se navzkrižja interesov pojavila med lokalnim prebivalstvom in upravljavci, sedaj pa se konflikt pojavlja ob istočasnem naraščanju turizma in želji po varovanju narave.Kjučne besede: morfometrija soteske, glaciokras, okrogle konkrecije, depopulacija podeželja, geoturizem, narodni park.

The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece

The Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars

The Greek Database of Seismogenic Sources (GreDaSS): state-of-the-art for northern Greece

The Greek Database of Seismogenic Sources (GreDaSS) is a repository of geological, tectonic and active-fault data for the Greek territory and its surroundings. In this report, we present the state-of-the-art of an on-going project devoted to the building of the GreDaSS, which represents the results of decades of investigations by the authors and a myriad of other researchers working on the active tectonics of the broader Aegean Region. The principal aim of this international project is to create a homogeneous framework of all of the data relevant to the seismotectonics, and especially the seismic hazard assessment, of Greece and its surroundings, as well as to provide a common research platform for performing seismic hazard analyses, modeling and scenarios from specific seismogenic structures. In particular, we introduce and synthetically describe the results obtained (and included in the database) to date in the northern sector of continental Greece and the Aegean Sea. As a first step we collected all available (both published and unpublished) historical and instrumental seismicity data relevant to the determining of the causative faults. Following the experience of recent 'surprising' earthquakes (e.g. 1995 Kozani, and 1999 Athens), we realized the deficiency of such an approach, and decided to also include in the GreDaSS active faults (i.e. seismogenic sources) recognized on the basis of geological, structural, morphotectonic, paleoseismological and geophysical investigations. A second step is the critical analysis of all of the collected data for the extraction of the necessary seismotectonic information, enabling the recognition of as many seismogenic sources as possible, as well as their characterization and parameterization. The most updated version of the database consists of numerous seismogenic sources that are categorized into three types: composite, individual, and debated. In this report, we describe the major seismotectonic properties of all of the composite seismogenic sources and individual seismogenic sources in northern Greece, which imply the partitioning of the area into five sectors that show similar internal behavior. Northern Greece was chosen as a pilot area because the parameters and accompanied metadata of its seismogenic sources show a high level of confidence and completeness. The amount of information and the degree of uncertainty is different for the three types.

An updated database of Holocene relative sea level changes in NE Aegean Sea

The reconstruction of Holocene relative sea levels has several implications, ranging from the investigation of coastal vertical movements to the calibration of earth rheology models and ice sheet reconstructions. The North Eastern Aegean Sea is among the tectonically complex sectors of the Eastern Mediterranean, mainly influenced by the activity of the North Anatolian Fault. In this paper, we created a relative sea level (RSL) database by expanding upon the previous compilation with recently published geological and archaeological data. We reconstruct the RSL history in those Aegean coastal sectors located within the South Marmara microplate, a broad shear zone located between western Anatolia and central Greece and affected by dominant strike-slip faulting, at times combined with a normal component. Then, we compared it with the RSL histories obtained for the surrounding coastal sectors. The analysis of the database indicated that it is not possible to define a common Holocene RSL curve for the entire NE Aegean, as RSL history here is majorly influenced by changes in deformation patterns. In addition, data in our database are consistent with a continuous RSL rise in the last 6.0 ka BP in the whole NE Aegean Sea and cannot support the hypothesis of a mid-Holocene RSL highstand in the area. Finally, we present our best estimates of late Holocene rates of RSL prior to any possible acceleration during the twentieth century in the broad area of NE Aegean. Here we identified the fastest rising rate (~0.9 mm a-1) in that sector whose active tectonic deformation is mainly controlled by the North Anatolian Fault activity. © 2013 Elsevier Ltd and INQUA

The Geological Structure and Tectonic Complexity of Northern Thessaly That Hosted the March 2021 Seismic Crisis

Knowing the rich presence of active faults in northern Thessaly and the lack of any significant seismic activity since at least the mid-1940s, the 2021 seismic sequence did not surprise us. What did surprise us was the fact that (i) despite the great knowledge of the neotectonic faults in the area, the causative faults were unknown, or almost unknown; (ii) the direction of the 2021 faulting was different than the expected, and given that the focal mechanisms showed almost pure normal dip-slip motion, the extensional main axis was also different than the one we thought we knew for this area; and (iii) besides the co-seismic ruptures that occurred within the Domeniko-Amouri basin and along the Titarissios River valley, there is evidence of rupturing in the alpine basement of Zarkos mountains. After thoroughly reviewing both the alpine and neotectonic structural setting and all the available literature concerning the seismotectonic data and interpretations of the 2021 sequence, including investigations of our own, we end up in a complex tectonic setting with older alpine structures now operating as inherited faults, and we also suggest the possible occurrence of a roughly N-dipping, low-angle, detachment-type fault. This fault runs below Mt Zarkos, reaching at least the Elassona Basin, with splay faults bifurcating upwards from the main fault zone. Following this complexity, rupture of the first mainshock must have chosen a split route reaching the surface through the gneiss rocks of Zarkos and almost (?) reaching the basinal sediments of the local tectonic depressions. This seismic sequence is a perfect case study to shed some light on the tectonic and rupture processes in the context of both geodynamics and seismic hazard assessment