Search Results (12)

Understanding how strain is transferred across the interior of tectonic plates is fundamental to quantifying lithospheric deformation. The Central Anatolia Transition Zone (CATZ), situated between the North and East Anatolian fault systems, provides a unique natural laboratory for investigating how continental deformation evolves from localized faulting to distributed shear. In this study, we integrate InSAR analysis with Global Navigation Satellite System (GNSS) velocity data, and stress tensor inversion with supporting gravity and seismic datasets to characterize the geometry, kinematics, and geodynamic significance of the CATZ. The combined geodetic and geophysical observations reveal that the CATZ is a persistent, left-lateral deformation corridor (i.e., elongated zone of Earth’s crust that accommodates movement where the landmass on the opposite side of a fault system moves to the left relative to an observer) accommodating ~4 mm/yr of shear between the oppositely moving eastern and western sectors of the Anatolian Plate. Spatial coherence among LiCSAR-derived shear patterns, GNSS velocity gradients, and regional stress-field rotations defines the CATZ as a crustal- to lithospheric-scale transition zone linking the strike-slip domains of central Anatolia with the subduction zones of the Hellenic and Cyprus arcs. Stress inversion analyses delineate four subzones with systematic kinematic transitions: compressional regimes in the north, extensional fields in the central domain, and complex compressional–transtensional deformation toward the south. The CATZ coincides with zones of variable Moho depth, crustal thickness, and inferred lithospheric tearing within the retreating African slab, indicating a deep-seated origin. Its S-shaped curvature and long-term evolution since the late Miocene reflect progressive coupling between upper-crustal faulting and deeper lithospheric reorganization. Recognition of the CATZ as a lithospheric-scale transition zone, rather than a discrete active fault, refines the current understanding of Anatolia’s kinematic framework. This study demonstrates the capability of integrated satellite geodesy and stress modeling to resolve diffuse intra-plate deformation, offering a transferable approach for delineating similar transition zones in other continental regions. Full article

This study delves into the southern Aegean regionwhere the subduction of the oceanic Mediterranean lithosphere under the Aegean continental one takes place. This region is considered one of the most active ones in the eastern Mediterranean Sea due to intense tectonic movements in the Late Quaternary. More than 1200 manually revised events from 2018 to 2023 have been used in order to obtain the 3D structure of body-wave velocity and V_P/V_S ratioto 80 km depth through earthquaketomography. A series of resolution tests have been performed and demonstrated fair resolution of the derived velocity structures in the area of interest. The derived anomalies of body-waves (dV_P, dV_S) and V_P/V_S ratio provided important information about the southern Aegean regional tectonics and secondarily active faults of smaller scale (>20 km). The region is marked by significant low-velocity anomalies in the crust and uppermost mantle, beneath the active arc volcanoes. The seismicity related to the Hellenic Subduction Zone (HSZ) is connected to a low-angle positive anomaly of V_P and V_S, correlated withthe observed intermediate-depth seismicity (H ≥ 40 km) in this part of the study area. This result could be related to the diving HSZ slab. Full article

Lefkada and Corfu old towns are located in the western part of Greece, in the Ionian Sea. Their proximity to the Hellenic subduction zone (HSZ) is the reason for their intense seismicity. The main goal of this study was the estimation of the geotechnical characteristics of the subsurface, with the contribution of applied geophysical techniques. Therefore, seismic refraction tomography (SRT) and multichannel analysis of surface waves (MASW) were applied. A total of thirty-three (33) seismic and geoelectrical profiles were performed in both towns in order to evaluate the geotechnical characteristics of the subsurface formations. Additionally, subsurface resistivity distributions were investigated with the application of electrical resistivity tomography (ERT). Some important elastic moduli were calculated through the combination of estimated seismic wave velocities and laboratory density measurements. The horizontal distribution of seismic velocities and mechanical properties (σ, E, K, G) of Corfu town was illustrated in maps, for the depth of 5 m. The geophysical interpretation also revealed that Lefkada’s subsurface consists of only one compact geological formation, with little or no variation of its geophysical-geotechnical characteristics. Beyond that, the ground type classifications for the two towns were determined according to the European Committee for Standardization Eurocode 8, based on V_S30 values. Full article

Combined with eustatic sea-level changes, uplifted Quaternary marine terraces provide insight into the tectonics of coastal areas. Cephalonia Island lies 35 km off the western coast of mainland Greece and 15 km northeast of the Hellenic subduction zone. Late Pleistocene eustatic sea-level oscillations and the long-term tectonic movements are imprinted on the landscape of the southern part of the island, in the form of seven uplifted marine terraces. In the present study we aim to identify and map in detail these terraces, applying Digital Elevation Model analysis, utilizing Geographic Information Systems techniques and extensive fieldwork. The GIS-based analysis combined with field geomorphological observations revealed a sequence of seven marine terraces at the southern part of the main island ranging in elevation between 4 m and 176 m asl. Microscope, petrological and microgeomorphological analyses on two caprock samples suggest strong marine influence during the deposition of the sediments covering the marine terraces. The age of the formation of the 32 m marine terrace was assigned to the MIS 3e, based on OSL dating of a caprock sample, and an average uplift rate of 1.4 ± 0.35 mm a⁻¹ was calculated for the last 61 ± 5.5 ka. Assuming a uniform uplift rate for the Late Pleistocene allowed us to correlate the marine terrace with the sea-level highstands and constrain their ages. Full article

Seismicity in the Ionian Sea (W. Greece) is mainly generated along the Cephalonia–Lefkada Transform Fault Zone (CLTFZ) in the central Ionian, and on the northwestern termination of the Hellenic subduction margin in the south. Joint pre-, co- and post-seismic ground deformation and seismological analysis is performed at the broad Ionian area, aiming to homogeneously study the spatiotemporal evolution of the activity prior to and after the occurrence of strong (M > 6) earthquakes during the period of 2014–2018. The 2014 Cephalonia earthquakes (Mw6.1 and Mw5.9) were generated on a faulting system adjacent to CLTFZ, causing local ground deformation. The post-seismic sequence is coupled in space and time with the 2015 Lefkada earthquake (Mw6.4), which occurred on the Lefkada segment of the CLTFZ. Co-seismic displacement was recorded in the broader area. Seismicity was concentrated along the CLTFZ, while its temporal evolution lasted for several months. The 2018 Zakynthos earthquake (Mw6.7) caused regional deformation and alterations on the near-velocity field, with the seismicity rate remaining above background levels until the end of 2021. In the northern Ionian, convergence between the Apulian platform and the Hellenic foreland occurs, exhibiting low seismicity. Seismic hazard assessment revealed high PGA and PGV expected values in the central Ionian. Full article

Marine terraces are geomorphic markers largely used to estimate past sea-level positions and surface deformation rates in studies focused on climate and tectonic processes worldwide. This paper aims to investigate the role of tectonic processes in the late Quaternary evolution of the coastal landscape of the broader Neapolis area by assessing long-term vertical deformation rates. To document and estimate coastal uplift, marine terraces are used in conjunction with Optically Stimulated Luminescence (OSL) dating and correlation to late Quaternary eustatic sea-level variations. The study area is located in SE Peloponnese in a tectonically active region. Geodynamic processes in the area are related to the active subduction of the African lithosphere beneath the Eurasian plate. A series of 10 well preserved uplifted marine terraces with inner edges ranging in elevation from 8 ± 2 m to 192 ± 2 m above m.s.l. have been documented, indicating a significant coastal uplift of the study area. Marine terraces have been identified and mapped using topographic maps (at a scale of 1:5000), aerial photographs, and a 2 m resolution Digital Elevation Model (DEM), supported by extensive field observations. OSL dating of selected samples from two of the terraces allowed us to correlate them with late Pleistocene Marine Isotope Stage (MIS) sea-level highstands and to estimate the long-term uplift rate. Based on the findings of the above approach, a long-term uplift rate of 0.36 ± 0.11 mm a⁻¹ over the last 401 ± 10 ka has been suggested for the study area. The spatially uniform uplift of the broader Neapolis area is driven by the active subduction of the African lithosphere beneath the Eurasian plate since the study area is situated very close (~90 km) to the active margin of the Hellenic subduction zone. Full article

Strong motion sensor networks deployed in metropolitan areas are able to provide valuable information for civil protection Decision Support Systems (DSSs) aiming to mitigate seismic risk and earthquake social-economic impact. To this direction, such a network is installed and real-time operated in Chania (Crete Island, Greece), city located in the vicinity of the seismically active south front of the Hellenic Subduction Zone. A blend of both traditional and advanced analysis techniques and interpretation methods of strong ground motion data are presented, studying indicative cases of Chania shaking due to earthquakes in the last couple years. The orientation independent spectral acceleration as well as the spatial distribution of the strong ground motion parameters such as the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Peak Ground Displacement (PGD) and Arias Ιntensity observed at the urban area of Chania are presented with the use of a Geographic Information System (GIS) environment. The results point to the importance of the strong ground motion networks as they can provide valuable information on earthquake hazards prior to and after detrimental seismic events to feed rapid systems supporting civil protection decisions for prevention and emergency response. Full article

The Lavrion area corresponds to the western part of the Attic-Cycladic metamorphic belt, in the back-arc region of the active Hellenic subduction zone. Between the Eocene and the Miocene, metamorphic rocks (mainly marbles and schists) underwent several stages of metamorphism and deformation due to collision and collapse of the Cycladic belt. Exhumation during the Miocene was accommodated by the movement of a large-scale detachment fault system, which also enhanced emplacement of magmatic rocks, leading to the formation of the famous Lavrion silver deposits. The area around the mines shows the stacking of nappes, with ore deposition mainly localized within the marbles, at marble-schist contacts, below, within, or above the detachment. The Lavrion deposit comprises five genetically-related but different styles of mineralization, a feature never observed in another ore deposit elsewhere, containing the highest number of different elements of any known mining district. The local geology, tectonic, and magmatic activity were fundamental factors in determining how and when the mineralization formed. Other key factors, such as the rise and the fall of sea level, which resulted from climate change over the last million years, were also of major importance for the subsequent surface oxidation at Lavrion that created an unmatched diversity of secondary minerals. As a result, the Lavrion deposit contains 638 minerals of which Lavrion is type-locality for 23 of them, which is nearly 12% of all known species. Apart from being famous for its silver exploitation, this mining district contains more minerals than any other district on Earth. The unique geological, mineralogical, and educational (mining, archaeological, and environmental) features suggest that it is highly suitable to be developed as a future UNESCO Global Geopark. Full article

Santorini Island, located in the Southern Aegean Sea, is prone to tsunamis due to its proximity to the Hellenic subduction zone, which is one of the major tsunamigenic areas. Characteristic events, such as those of 365 A.D. and 1303 A.D. greatly affected the coasts of the Eastern Mediterranean Sea, causing significant loss of life and construction damage. Tsunami disaster risk is nowadays significantly higher due to the increased exposure of the buildings as a result of the economic and touristic growth of the Aegean Islands. This study focuses on the eastern coast of Santorini, since its morphology and human presence amplify the necessity to assess its building vulnerability. After conducting an exposure analysis at the settlements of the eastern coast, Kamari poses the highest physical, social and economic relative exposure to any potential natural hazard. The main objective of this research is to quantify the building stock’s vulnerability to tsunami hazard. For this purpose, a “worst-case run-up scenario” was developed. Considering the history of tsunamis in the Aegean Sea, an extreme sea-level rise after a 10 m a.s.l. tsunami run-up, caused by an earthquake with M_w~8.5, was assumed. The relative vulnerability of the buildings in Kamari was calculated via the application of the Papathoma Tsunami Vulnerability Assessment (PTVA-4) analytic model. The results indicate that 423 buildings are within the inundation zone, 58% of which are characterized as highly and very highly vulnerable to tsunamis, revealing the problematic characteristics of the building stock, offering important information to the decision-makers to mitigate a possible future tsunami impact. Full article

Significant seismicity anomalies preceded the 25 October 2018 mainshock (M_w = 6.8), NW Hellenic Arc: a transient intermediate-term (~2 yrs) swarm and a short-term (last 6 months) cluster with typical time-size-space foreshock patterns: activity increase, b-value drop, foreshocks move towards mainshock epicenter. The anomalies were identified with both a standard earthquake catalogue and a catalogue relocated with the Non-Linear Location (NLLoc) algorithm. Teleseismic P-waveforms inversion showed oblique-slip rupture with strike 10°, dip 24°, length ~70 km, faulting depth ~24 km, velocity 3.2 km/s, duration 18 s, slip 1.8 m within the asperity, seismic moment 2.0 × 10²⁶ dyne*cm. The two largest imminent foreshocks (M_w = 4.1, M_w = 4.8) occurred very close to the mainshock hypocenter. The asperity bounded up-dip by the foreshocks area and at the north by the foreshocks/swarm area. The accelerated foreshocks very likely promoted slip accumulation contributing to unlocking the asperity and breaking with the mainshock. The rupture initially propagated northwards, but after 6 s stopped at the north bound and turned southwards. Most early aftershocks concentrated in the foreshocks/swarm area. This distribution was controlled not only by stress transfer from the mainshock but also by pre-existing stress. In the frame of a program for regular monitoring and near real-time identification of seismicity anomalies, foreshock patterns would be detectable at least three months prior the mainshock, thus demonstrating the significant predictive value of foreshocks. Full article

Kythira Island is situated at the western Hellenic Arc, which is a region of very high seismicity and tectonic activity. On 8 January 2006, a large seismic event of M_w = 6.7 occurred close to Kythira, in association with the Hellenic subduction zone. We present an extensive multi-temporal interferometry study of ground displacements in Kythira Island exploiting SAR data of a decade, from 2003 to 2009, and from 2015 to 2019. The line-of-sight displacement field for the 2003–2009 time period presents small-scale displacements that do not exceed −3 mm/y, identified to the East of Kythira’s airport, and 3 mm/y in the central part of the island. We exploit then Sentinel-1 data from 2015 to 2019, of both descending and ascending Sentinel-1 SAR imaging modes to decompose the line-of-sight measured deformation to vertical and east–west motion components. Higher vertical displacement rates characterize the central part of the island, with a maximum value of 5 mm/y. This short-term uplift rate exceeds by an order of magnitude the long-term geologic uplift rate of ~0.13 mm/y found in the island during the Quaternary. We discuss possible regional geophysical explanations for this discrepancy. Strike-slip components are detected in the N–E coast of the Potamos village, where horizontal displacements occur, with an east-ward trend and a maximum value of −3 mm/y. These insights are valuable input for the systematic monitoring of this high seismic risk island and the dynamic assessment of its hazard potential. Full article

We use Interferometric Synthetic Aperture Radar (InSAR) to study the Cephalonia–Lefkada Transform Fault Zone (CTF) in the Ionian Sea. The CTF separates continental subduction to the north from oceanic subduction to the south, along the Hellenic Subduction Zone. We exploit a rich multi-modal radar dataset of the most recent major earthquake in the region, the 17 November 2015 Mw 6.4 event, and present new surface displacement results that offer additional constraints on the fault segmentation of the area. Based on this dataset, and by exploiting available information of earthquake relocation, we propose a new rupture process for the 2015 sequence, complementary to those published already. Our modelling includes an additional southern fault segment, oblique to the segment related with the mainshock, which indicates that the CTF structure is more complex than previously believed. Full article