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Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave's shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis. [ABSTRACT FROM AUTHOR]

The Northern Thessaly Basin in central Greece ranks amongst the most well pronounced extensional (graben) basins in the backarc Aegean Sea region, with well-mapped faults having an ∼E–W orientation, compatible with the ongoing predominant ∼N–S extension. The southern margin of the basin is bounded by major faults associated with strong (M 6 to M 7) earthquakes, whereas along its northern margin, strong events are more scarce, in the documented catalogues. Along this northern margin, a weak, albeit persisting foreshock activity, culminated within 3 d, to an M w 6.3 earthquake on 3 March 2021 associated with a 15-km-long NE dipping fault segment. It was followed the next day, by the second M w 6.0 main shock associated with a 13-km-long NE dipping fault segment and 9 d later by an M w 5.5 earthquake associated with an 8-km-long SW dipping fault segment, with its aligned epicentres, showcasing the cascade type activation of adjacent fault segments. The sequence, evolved to be very productive, with aftershocks extending ∼50 km along a ∼NW–SE trending narrow seismic zone. All events indicate pure normal faulting, with an NNE–SSW oriented extensional axis, oblique to our previous consensus of the prevalence of ∼N–S extension. This observation documents that inherited fault fabric can be reactivated within the modern tectonic stress field. We use high-quality seismological data, alongside Interferometric Synthetic Aperture Radar (InSAR) methodology and Global Navigation Satellite System (GNSS) data, to study the temporal and spatial evolution of the sequence, and to provide inferred kinematic models that describe the complexity of the seismic process, in terms of heterogeneous slip distribution, activated fault planes, fault geometry and displacement field. Cross-sections show that the activity defines the crustal seismogenic layer at depths between 5 and 10 km, associated with low-angle fault segments dipping to the NE. Other faults, both antithetic and secondary ones, appear active and accommodated aftershocks clusters. Using our preferred finite fault source model, we calculated the changes of Coulomb failure stress on the neighbouring faults. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

On October 30, 2020, a strong earthquake (Mw6.6-7.0) occurred offshore, just north of Samos Island, causing life losses, injuries and damages, especially on the Turkish side. The broader area is characterized by a complex geodynamic setting with both rich seismic history and numerous active faults of different direction and kinematics. The first aim of this study is to define the seismic source of the mainshock, based on seismological and geodetic data (GPS measurements and originally processed GNSS records), as well as our field observations on Samos Island few days after the mainshock. The integration of this information leads to a N-dipping normal fault (Kaystrios fault) that controls the central-northern coast of Samos Island. We modelled the seismic source and calculated the theoretical dislocation (using the Okada formulae) on the surrounding GPS/GNSS stations, comparing it with the measured values. The results are very encouraging, especially on the station installed on Samos Island, giving confidence to our source model. We then used our seismic source to study the spatiotemporal evolution of the aftershock sequence by exploiting published seismological data (focal mechanisms and two seismic catalogues, one of which with relocated hypocentres) and our calculated Coulomb static stress changes caused by the mainshock. This comparison suggests that more faults than the Kaystrios fault were involved in the aftershock sequence. In order to investigate possible triggering and/or delay scenarios of the mainshock on nearby faults, the Coulomb stress changes are also studied showing various results according to each receiver fault. [ABSTRACT FROM AUTHOR]

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Copyright of Bulletin of the Geological Society of Greece is the property of Geological Society of Greece and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 (<2.6 km depth) from boiling hydrothermal fluids. A later condensation of vapor-rich inclusions resulted in a moderately saline fluid (8.4–11.2 wt % NaCl equiv) at temperatures between 311 and 392 °C, which were related to sericitic alteration, D-type veins, and associated metallic mineralization. Subsequent dilution of the moderately saline fluid at lower temperatures (205–259 °C) produced a less saline (1.4–2.9 wt % NaCl equiv.) fluid, which is likely associated with the late epithermal overprint. [ABSTRACT FROM AUTHOR]

The broader Corinth Gulf region is characterized by a notable active tectonic regime, associated with multiple active fault zones. The continuous N-S extensional tectonics of the area is responsible for the roughly E-W trending active normal fault zones, while individual fault segments are associated with seismic events. Satellite geodesy is a qualitative and quantitative means of estimating the tectonically active setting, based on the recorded motions. The study area is monitored by 14 permanent GPS/GNSS stations, collecting primary geodetic data for a 7-year time period (2008-2014). A 30-sec observation rate was performed, resulting in the extraction of the GPS/GNSS velocity values. The primary geodetic data were processed by applying the triangulation methodology, based on the combination of three different GPS/GNSS stations data, which were considered as the triangle vertices. Triangulation methodology led to the construction of 26 different triangles, while for each of them a series of parameters was determined. In particular, the extracted parameters are: a) Maximum Horizontal Extension, b) Total Velocity, c) Maximum Shear Strain and d) Area Strain. The extracted results are expected to approach, qualitatively and quantitatively, the interpretation of the tectonic regime, as well as to determine new, seismic-related, tectonic features. [ABSTRACT FROM AUTHOR]

Copyright of Acta Carsologica is the property of Scientific Research Centre of Slovenian Academy of Sciences & Arts and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)