42 research outputs found

    QUATERNARY DEFORMATION OF THE MAVROPIGI LIGNITE FIELD (WESTERN MARGIN OF PTOLEMAIS - KOZANI GRABEN, NW MACEDONIA, GREECE)

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    The present study aims to analyse in details the tectono-sedimentary processes of the western borderline of the intra-continental graben of Ptolemais-Kozani in NW Macedonia, given the presentday mining activity of Public Power Corporation. Field studies in combination with drilling analysis revealed the extremely geometrical complexity of the sedimentary fill as the result of the recent Quaternary deformation. Bearing in mind, the recognition of left-lateral strike-slip component of movement in the western border fault zone-Mavropigi shear zone, the geometrical coincidence of the morphological shapes of the present-day morphology-of the top-of the bottom of the Pliocene earthy lignite sequence and of the sub-surface morphology of the pre-Cretaceous Pelagonian basement as well as the discovery of several reverse faults in the surrounding area have allowed us to accept the action of a composite Quaternary deformational pattern. For the first time in NW Macedonia, ductile-brittle type macrostructures (mega-anticlines) with NE-SW axis direction are confirmed, showing the simultaneous and progressive action of ductile and brittle deformation of all the geological formations of the western borderline, sedimentary fill and metamorphic basement. The aforementioned geometrical complexity and also the observed field structures strongly reveal the action of a rotational couple-type stress field in Ptolemais-Kozani graben, enclosed in the incapiate in-type deformation of NW Macedonia. In this framework, the occurrence of the extensional post-orogenic structures, which seems that they have been overestimated by previous researchers in the literature, is considered of secondary importance and constitutes part and expression of the complicated Quaternary tectonic structures of the sedimentary fill. This complex deformational pattern controls and also defines the spatial distribution of the lignite reserves in the Mavropigi Lignite Field with a southward increasing of them as well as causes regions with a composite or a simple post-orogenic geometry and evolution, directly reflected by the sub-surface geometry of the Pliocene lignite sequence. The aforementioned complicated geometry is of great importance, either for the planning and the future expansion of the Mavropigi Lignite Field in the western borderline, or for the better approach of the intra-plate deformational processes of Ptolemais-Kozani graben

    Paleoseismological investigations along the Kera fault zone, Western Crete: implications for seismic hazard assessment

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    The island of Crete is the principal landmass in the Aegean arc system. Collision of the Euroasian plate in the north and the African plate in the south gives rise to the subduction related deformation along the Hellenic arc. As a result of the complex deformation, the area is characterized by high seismic activity. Paleoseismic investigations performed along the Kera fault scarp, which is part of a N-S oriented fault system along the Spatha peninsula (NW-Crete), show clear evidence of repeated normal faulting events. Five distinct episodes of faulting are observed. The first two are probably of Middle-Miocene or younger age representing older tectonic episodes, whereas the last three indicate co-seismic displacements most likely during the Pleistocene and Holocene. This is in good agreement with the previous estimates of Holocene average slip rate and the recurrence time estimate of large earthquakes in the order of ca. lmm/yr and 3000yrs, respectively. The Kera fault represents a NE-SW oriented bend in a N-S fault system and therefore has a minor left-lateral strike-slip component. During the 1980's at least three earthquakes could be associated with the Kera fault. More recently, in 1999, there were three small (with magnitudes between 3.0-4.5) offshore events that are probably associated with the same fault system in the offshore extension (to the north) of the N-S oriented faults along the Spatha peninsula. The existence of these earthquakes as well as the recent paleoseismic results clearly demonstrates the need of revising the seismic hazard assessment of the area. The length of the N-S oriented fault system, where the Kera fault represents the middle segment, reaches to a total of 30 km., and is capable of generating an earthquake of magnitude in the range 6.0-6.7. Such a (shallow) earthquake occurring at a short distance to the densely populated north-western coast of Crete is likely to have significant consequences

    Predicting Ground Subsidence Induced by Pumping Combining Space Measurements and Geotechnical Modeling: Application in the Thessaly Region, Greece

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    Space technology is a new technology that provides cost-effective measurements of past displacement data. Based on these displacement measurements, within the framework of the European Space Agency’s GMES Terrafirma Project, an improved geotechnical design approach is proposed combining geotechnical modelling and space measurements to predict ground subsidence induced by the lowering of the water table. Then the proposed methodology is applied to predict future displacement at the Thessaly plain - Carla region, Greece due to excessive pumping

    Neotectonic folds in the central-western Peloponnese, Greece

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    The western Peloponnese, being very close to the Hellenic Trench, is one of the most active areas in Greece. The study area is located at the central western part of Peloponnese and it is developed in a NNW-SSE direction along 45 km, parallel to the Ionian Trench, which occurs at a distance of only 30-40 km to the west. Based on the morphotectonic studies of the neotectonic macrostructures of the central-western Peloponnese in many scales, it was concluded that the main neotectonic mega-structure is the "Megalopolis-Lykaeon-Minthi-Tetrazio Composite Morphotectonic Structure" (MELYMITE CMS) (1st order structure). The neotectonic deformation is expressed not only by faults, but also by folds which in some cases are the principal structures of the neotectonic deformation. Neotectonic folds occur in the Alpine formations as well as in the post-Alpine ones in various scales. The folds, and the ductile deformation in general, are not easily observed on the surface because of the intense presence of brittle tectonics. A rotational couple stress-fi eld could satisfactory incorporate and explain the brittle-ductile neotectonic structures of the area. © 2008 E. Schweizerbart'sche Verlagsbuchhandlung
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