The region hosts major continental transform faults, including the North Anatolian, East Anatolian and Dead Sea Faults, along with the Hellenic Arc, all of which have produced devastating earthquakes both in historical times and in the recent past. The interplay between shallow fault activity and deep-seated mantle processes remains a matter of debate, and recent destructive earthquakes have emphasized how critical it is to improve comprehension of seismic cycle and the geodynamic process that controls it.
This session welcomes multidisciplinary contributions — including neotectonics, seismology, tectonic geodesy (e.g. GNSS, InSAR), paleoseismology, tectonic geomorphology, structural geology, remote sensing, and geodynamic modelling — to advance our understanding of active tectonics and geodynamics in the Eastern Mediterranean. We particularly encourage submissions from early career researchers.
The Hellenic forearc is one of the least understood forearc systems globally due to limited availability of high-resolution imagery of its deep structure, especially landward of the Mediterranean Ridge. This has resulted to ambiguity about the origin of its key structural and morphotectonic features, the location of the active subduction trench, the relationship between different fault types within its forearc and to whether this system is capable of generating large (M>8) subduction earthquakes and associated tsunamis. Here, we combine widely spaced high-resolution multichannel seismic-reflection profiles with seafloor morpho-bathymetric analysis and earthquake moment-tensors to investigate the structure and post-Messinian (0–5.9 Ma) fault kinematics in the Hellenic forearc. Our work provides, for the first time, strong evidence for the presence of active thrust faults along the inner forearc, from the backstop of the Mediterranean Ridge to the Hellenic Trough. Many thrusts are imaged to splay from the subduction plate-interface, at depths of 6–8 s (TWT), while normal and strike-slip faults commonly form in the upper-crust landward of the 20 km slab-isodepth, and abut against thrust hanging-walls. Observed fault patterns are supported by seabed fault-scarp analysis and are consistent with the distribution and kinematics of earthquake moment-tensors. Analysis of fault-intersections at depth suggests that forearc kinematics are characterized by a fault hierarchy, in which normal and strike-slip faults commonly form as secondary structures above active thrusts, accommodating oblique plate-convergence. Our analysis also highlights a structural division of the forearc into landward- and seaward-verging thrusts, similar to that recorded along the Cascadia and Sumatra margin, with the Hellenic troughs accommodating their geometric transition. Thrust vergence variability likely results from the northward steepening of the underlying plate-interface and marks the across-forearc transition from aseismic to seismic-slip. These significant revisions in understanding of the Hellenic Subduction System and its upper-plate structures are expected to flow into future geodynamic, hydrocarbon-exploration and earthquake hazard models.
How to cite: Mouslopoulou, V., Begg, J., Polonia, A., Nicol, A., Reston, T., Cesca, S., and Gasperini, L.: The Hellenic Subduction System: A revised view of its structure and kinematics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4914, https://doi.org/10.5194/egusphere-egu26-4914, 2026.
An offshore M5.9 earthquake occurred on 29 March 2024 in the western Hellenic subduction system near the Strofades Islands. The mainshock and the related sequence occurred during a period of unusually dense onshore broadband seismic station coverage across the Peloponnese, including a temporary station deployment operated by the Ruhr University Bochum, Adria Array temporary stations, and permanent stations from the Hellenic Unified Seismological Network. Here we present a study of the seismotectonic context of the M5.9 sequence that capitalizes on the dense coverage and its fortuitous location to investigate subduction dynamics in the region, including interactions between the upper and lower plates and the strength of the megathrust. We compute high-resolution hypocentral locations and focal mechanism solutions that point to an association of the earthquake sequence with the lower plate. The absence of triggered upper-plate seismicity, together with contrasting stress orientations between the overriding and subducting plates, are consistent with a decoupled stress field between the two plates and suggest a weak megathrust interface.
Our analysis of the distribution of high-precision hypocenter locations and focal mechanism solutions is coupled with an interpretation in the context of local stress field and previously mapped intraslab faults. High-precision hypocenter locations and focal mechanisms indicate rupture on a NNE–SSW striking, left-lateral strike-slip fault within the slab. P- and T-axis focal mechanism orientations differ from those of nearby interplate and upper-plate earthquakes, consistent with the intraslab nature of the sequence and indicative of a distinct stress regime. The stress pattern of the M5.9 earthquake sequence lies approximately orthogonal to the NE–SW shortening direction of the upper plate and reflects arc-parallel shortening within the lower plate, similar to that observed for intermediate-depth earthquakes in the Aegean. The orientation of the intraslab stress field relative to the plate margin suggests that slab rollback controls the intraslab stress regime by reducing horizontal compressional stress normal to the margin. Our results suggest that previously mapped intraslab faults, if present, play a limited role in controlling the intraslab stress field, and that a weak megathrust limits interaction and stress transfer between the lower and upper plates in the shallow portion of the subduction zone.
How to cite: Bocchini, G. M., Essing, D., Nikolopoulou, I., Dielforder, A., Roth, M. P., Serpetsidaki, A., Sokos, E., Evangelidis, C. P., and Harrington, R. M.: Stress field and megathrust strength in the Western Hellenic subduction system: insights from the 2024 Mw 5.9 Strofades earthquake sequence, Greece., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3752, https://doi.org/10.5194/egusphere-egu26-3752, 2026.
Two very strong earthquakes and many aftershocks spread havoc in southeast Turkey in February 2023, and indeed southeast Anatolia is an intricate geological region where two tectonic processes coincide, creating a complicated setting of the motion of the crustal blocks of the Levant and Anatolia and generating strong seismic activity. GPS measurements show clearly that not only does Anatolia move westwards, but that the velocity of that displacement increases westwards from ca. 20 mm/year to more than 30 mm/year. Furthermore, in the Aegean domain the offset changes its direction to southwest and its velocity continues to increase. It seems that the tectonic cause of Anatolia's westwards migration is the rollback of the Hellenic subduction front, which exerts a significant on the entire Anatolian crustal block. Geological and geophysical evidence for that pull is abundant throughout the Aegean domain. The Anatolian migration is accommodated along its large boundary faults, the North and East Anatolian Faults, which are very active seismically and converge in eastern Anatolia near Karliova.
The tectonics of the Levant is dominated by the Levant (Dead Sea) Rift and its mountainous flanks and oblique extension, where the left-lateral displacement along it is ca. 5 mm/yr. The tectonic regime there is dominated by the northwards propagation of the edge of the Red Sea incipient ocean, which changes its direction of advancement from northwestwards to northwards south of Sinai Peninsula. It seems that the Levant Rift ends its northwards propagation in north Lebanon, where its orientation shifts to the NE and the large fault is split into at least five secondary faults, and ends with the north edge of the Lebanese Baqa'a and its double mountain chains.
The tectonics of the terrain between the Lebanese mountainous domain and the East Anatolian Fault is controversial. Many researchers propose linkage of the Levant Rift and the East Anatolian Fault, which are both sinistral fault systems, by connecting the Yammouneh Fault, one of the Lebanese faults splay, with Masyaf Fault, a southwards extension of the East Anatolian Fault, and the eastern boundary of El-Ghab Rift.
Overall, it seems that the complex structural geology of the domain of eastern Anatolia and northern Levant reflects the complicated tectonics of the closure of NeoTethys Seaway, where the convergence of the Arabian segment of the African and the Eurasian tectonic plates take place. The eastern branch of the Seaway evolved into a collision zone between Arabia and the Bitlis-Zagros mountain belt, whereas subduction still prevails along the western NeoTethys between Africa and Europe. While the old ocean approaches its terminal stages, a new ocean is emerging in the Red Sea. The tectonic displacements indicate that the concept of "escape tectonics" seems poorly supported.
How to cite: Mart, Y.: The Hellenic subduction and the tectonics of the 2023 earthquakes of SE Anatolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3543, https://doi.org/10.5194/egusphere-egu26-3543, 2026.
RATIONALE
Following the 2023 February 6 disastrous earthquakes (Mw7.8 & Mw 7.7) that struck southern & central Türkiye, and northern & western Syria, an intense crust seismic sequence was triggered southwestern South Carpathians, Romania.
Hosted by Gorj County, north Târgu Jiu city, its capital, the sequence started with twin unusual high magnitude earthquake (ML5.2 on February 13, and ML5.7 on February 14) and continued for months with more than 4000 seismic events.
The area was known for quasi-continuous seismic activity, but surprising was the unusual intensity of earthquakes triggered and time extent of the sequence, which had a strong societal impact by scarring the population and provoking economic loss.
The paper brings some geophysics inferred ideas about tectonic circumstances for triggering and maintaining the long-lasting seismic sequence.
METHOD
Objective of the undertaken research was twofold: (i) to outline the overall tectonic setting of the area were the seismic sequence occurred, and (ii) to unveil more detailed structural circumstances of the largest magnitude earthquakes.
The approach was mainly based on gravity data mining and interpretation. In a first step, various filters were applied to the complete Bouguer anomaly, like low pass filtering and upward continuation for separating regional and local effects, horizontal and vertical gradients, for emphasising the faults track, etc.
In a second step, more advanced data processing, including inversion and forward modelling was conducted especially in areas of interest.
For better interpreting/understanding the obtained results, data provided by other geophysical investigations, like e.g., geomagnetism, seismology, or seismic tomography were also employed.
RESULTS
Among the main results it is worth mentioning: (i) overall location of seismicity along the northern flank of the westernmost segment of Getic Depression; (ii) earthquakes triggering mainly along faults striking WSW – ENE, as crustal echoes of the lithospheric contact between Moesian microplate (MoP) and Intra-alpine microplate (IaP); (iii) some earthquakes were also triggered along sub meridional faults.
The most active area appears as a highly fractured zone, overlaying an underground mass excess with high magnetisation, echoed by a gravity high associated with a geomagnetic anomaly. The basalt dykes cropping out in the area suggest the in-depth presence of mafic/ultramafic intrusive. The assumption is supported by the existence of a hidden high velocity body unveiled by seismic tomography.
FINAL REMARKS
To conclude, the unusual intense earthquakes of the Gorj sequence were likely triggered by a sudden increase of tectonic stress in the area due to an acceleration of the Black Sea microplate acting upon MoP. The NW push was WSW redirected along the transform contact between MoP and IaP. Among the others, the strain activated a seismic prone structure generated by the magmatic “diapirism” of an in-depth hidden mafic intrusive, likely belonging to Severine Nappe. The uplift of the mafic dome, had intensively fractured its crustal roof, creating a complex fault system along which earthquakes were triggered.
How to cite: Besutiu, L., Zlăgnean, L., and Isac, A.: Geophysics Based Ideas on Structural Setting of 2023 Seismic Sequence SW South Carpathians, Romania, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2322, https://doi.org/10.5194/egusphere-egu26-2322, 2026.
The recent 2025 sequence that occurred near Sındırgı, a town in Balıkesir (western Türkiye) started with a Mw 6.1 earthquake on August 10th (Sunday, 19:53 local time) on the westernmost part of the Simav graben. The normal faulting event was initially reported to be on the Sındırgı fault since the epicentre was located along its surface trace. As per the Turkish Active Faults Database, the fault is considered as one of the seven active segments of the Simav Fault Zone. Initial coseismic models calculated using the Sentinel-1 radar images acquired 24 hours after the earthquake revealed that the event could not have occurred on the proposed Sındırgı fault but on an unknown fault either to its south or its north. However, it also became evident that fault plane ambiguity could not be resolved using InSAR alone.
To aid in resolving this ambiguity and to monitor the distribution of the aftershocks TÜBİTAK Marmara Research Center’s Earth Sciences Research Group installed a temporary 16-station seismic network in the area. Using artificial intelligence techniques the spatiotemporal evolution of the seismic activity was determined using >30.000 relocated aftershocks. The seismic data favors the north dipping fault plane which intersects the surface about 7 km south of the Sındırgı fault.
A second Mw 6.1 event took place about two months later on October 27th (Monday, 22:48 local time). Both InSAR and the aftershocks distribution clearly exhibit that the event had occurred this time on a portion of a known fault to the east of the first mainshock. The coseismic models validate the strike slip dominant nature of the faulting that took place again within a depth range of 5 to 12 km on a ~60° south dipping fault.
The two earthquakes are the biggest to occur along the Simav Fault Zone since the 1970 M7.1 Gediz earthquake. In this study, the spatiotemporal evolution of the sequence will be discussed using both InSAR time series and seismic data as well as the elevated seismic hazard in the region where the activity was still continuing as of January 2026.
How to cite: Akoğlu, A. M., Ökeler, A., Ergin, M., Zor, E., Tapırdamaz, M. C., Sevim, F., Açıkgöz, C., Koşma, M., and Tarancıoğlu, A.: The 2025 Balıkesir Sındırgı (Türkiye) Mw 6.1 Doublet: Insights from InSAR and Seismology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20258, https://doi.org/10.5194/egusphere-egu26-20258, 2026.
The Büyük Menderes Graben (BMG) is a major E-W-oriented extensional basin in Western Anatolia, which exhibits along-strike variability. Yet, the factors controlling its internal asymmetry and the dominant boundary fault remain unresolved, mostly because previous studies of the BMG lack a three-dimensional perspective. This study integrates 2D seismic reflection data, well-log information, and 3D structural modeling between Aydın and Kuyucak to reassess the kinematic evolution of the graben.
Seismic reflection data reveal a distinctly asymmetric basin infill geometry, where early syn-rift deposits form clear wedge geometries and onlap patterns directed toward the southern graben-bounding fault, indicating that accommodation was primarily created along the southern margin. Overlying units show draping, subtle rollover structures, and thickening toward the south, further supporting continuous activity on the southern boundary fault throughout basin development, resembling a rift-climax system tracts described in the literature for half-grabens. The stratigraphic architecture and fault-sediment relationships observed on the N-S seismic sections are consistent with sandbox experiments and conceptual models depicting how major listric faults control the evolution of extensional basins.
A key outcome of this study is the recognition of a second control on basin asymmetry: a series of transverse, consistently east-dipping normal faults with dominant fault polarity is imaged on E-W seismic lines across the BMG. These structures generate localized depocenters, divergent reflection patterns, and westward-increasing thickness trends associated with progradational sediment input. When combined with GPS and InSAR results, both of which indicate a westward increase in extension rates across the BMG, the transverse faults are interpreted as the structural response to spatially variable extension, accompanied by a delta progradation throughout basin evolution.
The apparent symmetry observed on 2D seismic sections is primarily the result of the activation of high-angle normal faults along the northern margin during the Quaternary, which locally produced a more symmetrical basin infill geometry. The 3D structural model, on the other hand, further demonstrates that the basin deepens toward the southern boundary fault, whereas the northern fault retains its irregular geometry and limited subsidence. Geodetic slip-rate modeling also favors a north-dipping, active structure, aligning with the southern boundary fault. These observations suggest that the low-angle normal fault on the northern margin, commonly referred to as the Büyük Menderes Detachment Fault, is a relic structure of an earlier extensional phase, predating the formation of the current basin.
Overall, stratigraphic geometries, structural characteristics, and geodetic data converge on a coherent conclusion: the BMG evolved through multi-phase extension, dominated by the southern boundary fault, while transverse east-dipping faults and delta progradation enhanced internal basin asymmetry. These results refine the current understanding of rift evolution and faulting history in Western Anatolia and emphasize the role of spatially variable extension in shaping extensional basins.
Keywords: Eastern Mediterranean tectonics, Büyük Menderes Graben, extensional basin evolution, seismic reflection data, normal fault kinematics, active deformation.
How to cite: Oğuz, R., Kaymakcı, N., and Uzel, B.: Asymmetric Basin Evolution and Fault Kinematics in the Büyük Menderes Graben (Western Anatolia): Insights from 2D Seismic Reflection Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-602, https://doi.org/10.5194/egusphere-egu26-602, 2026.
The northern strand of the North Anatolian Fault (NAF) in the Sea of Marmara show a high seismic activity, including the recent Mw 6.2 earthquake of April 23, 2025, situated southwest of Istanbul. This fault zone is also characterized by different mechanical behaviours (i.e., locked vs creeping) and often associated with fluid evidences. In this study, we focus on the western part of the NAF in the Sea of Marmara, where aseismic deformation has often been reported to be at work. We use recordings from two piezometers, three ocean bottom seismometers (OBSs) from INGV, and three OBSs from KOERI, deployed around the Western High and the Tekirdağ Basin, to analyse the seismic activity between October 2013 and August 2014, and study potential links with pore pressure variations, a slow-slip event (SSE) that could have occurred during this period, and a Mw 4.6 earthquake that took place on November 27, 2013.This seismic network is completed by 11 land seismological stations to improve the microseismicity location accuracy.
In total, 2079 events were detected during the recording period, of which 409 events remained after double-difference relocation. We here identify a sequence of 21 highly-similar foreshocks during the week preceding the Mw 4.6 mainshock, aligned along sidewall faults in the Central Basin. This sequence coincides with the possible existence of a several months-long SSE propagating westwards, based on the interpretation of onshore geodetic data and offshore surface sediment pore pressure data. The foreshock occurrence, as well as the timing of the pore pressure variations measured within the fault valley, are compatible with the hypothesis that the modelled SSE impacted first the foreshock-mainshock sequence, and then fluid conditions within the NAF valley at the piezometer locations. Our results demonstrate that the combination of seafloor piezometry and seismology may prove very useful to study interactions between fluids and fault zone deformation, including preparatory phases of earthquakes.
How to cite: Tary, J.-B., Géli, L., Aiken, C., Rayer, C., Yamamoto, Y., Kalafat, D., Pinar, A., and Meral Özel, N.: Potential interactions between seismicity, fluid behaviours and aseismic deformation in the Western Sea of Marmara, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19632, https://doi.org/10.5194/egusphere-egu26-19632, 2026.
Seasonal modulation of seismicity has been reported in several regions worldwide, suggesting that earthquake occurrence may be sensitive to small, time-dependent stress perturbations. Such observations point to a range of hydro-meteorological processes that can generate seasonal stress changes, including variations in groundwater storage, rainfall, snow accumulation and melt, and sea-level fluctuations. Although the associated stress amplitudes are typically small, often of the order of a few kilopascals, they may influence the temporal distribution of seismicity. The mechanical response of faults to such forcings may involve different processes, including elastic loading and unloading, as well as poro-elastic and thermo-elastic effects.
Recently, seismicity associated with an active hydro-thermal system in the eastern Marmara Sea has been shown to respond to temporal variations in sea level. In this setting, sea-level changes induce small vertical loading variations that generate stress perturbations of a few kilopascals, sufficient to modulate seismicity timing in a critically stressed, fluid-rich crust. Here, we extend the study area to examine whether seasonal variations in the Marmara Sea level are associated with seismicity variations across the entire Marmara region, with a particular focus on seismic activity along the North Anatolian Fault Zone.
We analyze seismicity using an earthquake catalog covering the Marmara region for the period 2006–2024. The catalog is declustered using an adaptable Random Forest–based approach to isolate background seismicity and reduce the influence of aftershock sequences. Temporal variations in background seismicity are then examined using Multichannel Singular Spectrum Analysis (MSSA) and Multi-Seasonal Trend decomposition using Loess (MSTL), enabling the identification of independent seasonal components in seismicity rates. The resulting seasonal signals are compared with independent observations of surface loading, including GRACE-derived mass variations and Marmara Sea level changes derived from satellite altimetry and local tide-gauge records. We use these comparisons to assess the mechanisms controlling the seasonal variability observed in the seismicity catalog.
How to cite: Jara, J., Martínez-Garzón, P., Erkoç, M. H., and Dogan, U.: On the potential seasonality of seismicity along the North Anatolian Fault, Marmara region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11444, https://doi.org/10.5194/egusphere-egu26-11444, 2026.
On 6 February 2023, a major earthquake doublet (Mw 7.8 and Mw 7.6) ruptured the Anatolian plate boundary system. The first event occurred on the East Anatolian Fault (EAF), the principal plate-boundary zone between the Arabian and Eurasian plates, and the second ruptured the Çardak fault north of the western termination of the EAF. Continuous GNSS observations acquired in the months following the sequence indicate that deformation is not confined to the near-fault region: GNSS time series reveal substantial changes relative to pre-event interseismic velocities over distances of several hundred kilometers. These deviations extend northward across the North Anatolian Fault toward the Black Sea coast and westward across the Central Anatolian Plateau. Furthermore, seismicity rates appear to have been perturbed at locations far from the rupture area, and early postseismic investigations have suggested a measurable far-field signal, particularly to the west of the main rupture zones. Given the magnitude of the sequence and the dense regional geodetic coverage, this earthquake doublet provides an exceptional opportunity to investigate earthquake-cycle processes and to constrain spatial variations in rheological properties of fault zones and the surrounding lithosphere within an actively deforming tectonic setting.
We characterize the postseismic deformation of the far-field domain spanning from eastern Anatolia to the western Hellenic trench using regional GNSS networks. For each station, we isolate the transient component by removing the secular (interseismic) contribution using interseismic velocity fields estimated from long-duration pre-earthquake time series. We then extract coherent postseismic signals from the GNSS residuals using Independent Component Analysis (ICA) implemented in a variational Bayesian framework. To interpret the recovered far-field transients, we perform forward viscoelastic modeling to evaluate contrasts in crustal and lithospheric structure and rheology, and we test sensitivity to alternative coseismic rupture models derived primarily from space-geodetic constraints employing different strategies. We further examine the role of major far-field tectonic structures, particularly the Hellenic trench to the southwest and the Cyprus arc to the southeast, on the observed deformation patterns. Finally, we assess the relationship between postseismic deformation and seismicity by comparing far-field seismic activity with postseismic strain-rate fields inferred from the GNSS displacements, using the VDoHS (Vertical Derivatives of Horizontal Stress rates) approach.
How to cite: Özbey, V., Pierre, H., Jolivet, R., Barbot, S., Derand, P., Özeren, M. S., Michel, S., Chousinatis, K., and Ergintav, S.: Far-field postseismic deformation of the 2023 Kahramanmaraş earthquake doublet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11248, https://doi.org/10.5194/egusphere-egu26-11248, 2026.
Geodynamic models have been used to explore the controlling factors for rift and supradetachment basin formations. For the latter, a large (kms) scale (detachment) low angle normal shear zone accommodate the extension and an array of normal faults grow in various geometries and scales. Within the exception of few studies, extension velocities imposed on the lithospheric margins are considered to be constant throughout the model evolution. Nevertheless, this parameter can vary based on regional geodynamic factors, for example, during the lifetime of back-arc basins. Here we explore, how different speed functions can describe the extension rate and influence the tectonic deformation patterns within the lithosphere. ASPECT mantle convection models are used with varying speed functions, such as Vx = constant, linear, logarithmic, and parabolic. Namely, 2D approach provides a simple and focused way to study extension without adding extra complexity where models predict varying speed functions can change stress, the amount of lithosphere thinning, ductile-brittle high strain regions, and the overall deformation patterns. For example, the asymmetric nature of basin architecture can be transformed into symmetric style where both basin margins are controlled by rotating normal faults along horizontal axis. This condition is more favorable with logarithmic change in speed function. This study offers a simple first step toward understanding characterics of extension and basin tectonics in the eastern Mediterranean where trench retreat in the Aegean has accelerated from 1.7 cm/yr to 3.2 cm/yr during the last approximately 20 Ma.
How to cite: Şencer, O., Göğüş, O. H., Bodur, Ö., and Göğüş, Ö. D.: Multistage back-arc extension, basin tectonics and normal faulting in the eastern Mediterranean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1084, https://doi.org/10.5194/egusphere-egu26-1084, 2026.
The East Anatolian Fault Zone and Malatya Fault are located in eastern Türkiye and are among the most seismically hazardous faults in the region. After the 2023 M7.8 Kahramanmaraş/Pazarcik earthquake, the seismic risk in this area has further increased. We conducted magnetotelluric surveys in this region and obtained a profile containing 33 magnetotelluric measurement points. The apparent resistivity in this region is generally low, with an average apparent resistivity of several tens of Ωm, and shows little variation with depth. We used phase tensor technology to obtain two-dimensional deviation and phase tensor rotation invariants along the profile, and the conclusion is that the structure shows strong two-dimensionality in most areas along the profile, with only local areas showing strong three-dimensionality. We used the ModEM ADORA (Liu et al., 2024) magnetotelluric three-dimensional inversion system with arbitrary data rotation angles to invert the data, where the data maintained the acquisition direction and the grid was rotated 60°. This method can reduce the number of grid divisions, which not only saves computational time but also reduces the underdetermination of inversion. After calculations using different parameters and different grid divisions, we selected the result with better fitting degree and ultimately obtained the electrical structure profile across the Malatya Fault and East Anatolian Fault. The electrical structure reveals that the East Anatolian Fault is underlain by a boundary between high and low resistivity bodies. The formation of the Malatya Fault zone may be related to low-resistivity structures from deep sources that may be associated with fluids or high-temperature materials.
How to cite: Sun, X., Zhao, L., Beytut, B. B., Su, P., Sançar, T., Wei, Z., Zabcı, C., Shi, F., and Bao, Y.: New Magnetotelluric Study of the East Anatolian Fault Zone and Malatya Fault in Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1446, https://doi.org/10.5194/egusphere-egu26-1446, 2026.
Basins along continental strike-slip plate-boundary fault systems, such as the N-trending Dead Sea Fault (DSF), are key sites of strain partitioning, where regional motion is accommodated by a variable combination of along-strike slip, across-fault shortening or extension, and vertical movements. The Sea of Galilee (Kinneret) basin developed along the DSF in three main tectonic stages: it was first hijacked from the predecessor NW-trending Irbid rift during the Early Miocene, then deepened and reorganized as a pull-apart basin during the Late Miocene–Pliocene while being filled by local sedimentation, marine incursions and extensive basaltic infill, and since the Early Pleistocene it has evolved into a breached basin, expressed today as a narrow, asymmetric E–W-trending syncline bounded by the Eastern Marginal Fault and the Kinneret Diagonal Fault within a generally transpressive DSF regime.
Our new seismological analysis focuses on the mechanical behavior of the Kinneret Western Border Fault and its role in internal basin deformation. Using a high-resolution, relocated earthquake catalogue for 2018–2024 and Principal Component Analysis of hypocentral clusters, the study resolves active fault geometries and slip tendencies at unprecedented detail. Long-term seismicity aligns with the regional N–S tectonic grain (mean strike 187.5°, dip 59.2°), consistent with the broader DSF strike-slip kinematics, whereas the 2018 Sea of Galilee swarm activated a localized, rotated, low-angle bypass structure (strike 221.3°, dip 33.8°) that departs markedly from the conventional steep fault-plane models for the diagonal system. Existing tectonic models that infer a single, steeply dipping (~70°E) diagonal fault capture only part of the active structure; a nearly constant seismogenic thickness of ~150 m in both the long-term and swarm datasets indicates that the KWBF–diagonal system is better described as a volumetric damage zone rather than a discrete surface. These results demonstrate a structural decoupling between steady-state plate-boundary deformation and transient swarm dynamics and provide a new seismological framework for how evolving internal architectures of a breached pull-apart basin facilitate strain partitioning and ongoing development along the Dead Sea Fault.
How to cite: Nelaev, A., Lellouch, A., and Schattner, U.: Evolving architecture of a breached pull-apart basin: seismological constraints on the Kinneret Western Border Fault along the Dead Sea Fault, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3192, https://doi.org/10.5194/egusphere-egu26-3192, 2026.
As a result of the interaction between the Anatolian Plate and the African Plate to the south, and the Aegean microplate to the west, a complex extensional regime has developed across Western Anatolia. This dynamic tectonic framework causes significant crustal deformation and temporal strain accumulation, particularly along the active Fethiye–Burdur and Gökova fault zones. The Aegean region is considered one of the most seismically active areas worldwide. The Mw 6.7 earthquake that occurred within the Gulf of Gökova on 21 July 2017 represents one of the most recent destructive earthquakes in the region. Despite the pronounced seismic activity in this area, no active fault zones are mapped in this section of the Turkish Active Fault Map. The absence of mapped active structures has highlighted the necessity of detailed investigations into the region’s present-day tectonic deformation characteristics. Within the scope of this study, the aim is to determine crustal deformation and temporal strain accumulation based on Global Navigation Satellite System (GNSS) observations. For this purpose, the region has been monitored since 2021 through campaign-based GNSS measurements and data obtained from continuously operating GNSS stations.
In the study, GNSS data has been collected from 6 CORS-TR (Turkey National Permanent GNSS Network- Active) stations, 7 Turkey National Fundamental GNSS Network (TNFGN) sites, and 16 campaign GNSS sites. Four GNSS campaign measurements were carried out between 2021 and 2024 .The GNSS data were processed to generate coordinate time series and estimate station velocities using with Bernese GNSS Software version 5.4. Based on these results, a statistically significant velocity field was identified across the region, with horizontal southwest-directed velocities ranging from a maximum of 41.67 ± 1.76 mm/yr to a minimum of 22.05 ± 2.95 mm/yr. Also, temporal strain accumulation in the region was computed using a finite element method . The results indicate that the eastern and western parts of the region are characterized by different strain fields, and that the amount of strain has increased and expanded spatially over the observations.
This work is supported by TUBITAK CAYDAG Project Number 121Y300
How to cite: Turgut, M., Doğan, U., Özarpacı, S., Özdemir, A., Ayruk, E. T., Farımaz Ayruk, İ., Beytut, B. B., and Dikbaş, A.: Monitoring of Crustal Movements in the Eastern Gulf of Gokova with GNSS Measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3828, https://doi.org/10.5194/egusphere-egu26-3828, 2026.
Earthquakes occasionally rupture faults that were not previously recognised, raising the question of whether such structures represent newly formed faults or previously unidentified active faults with a history of repeated rupture. This debate is particularly relevant for the NE-striking eastern section of the 6 February 2023 Mw 7.5 Elbistan Earthquake rupture, referred to as the Yeşilyurt Fault. Unlike the better-known Çardak Fault to the west, the Yeşilyurt Fault was not mapped in the official Active Fault Map of Türkiye and lacks data regarding its paleoseismicity and morphotectonic evolution.
In this study, we introduce a novel, high-resolution, non-invasive, and relatively time- and cost-effective approach to investigate the rupture history at a surface-rupture site of the Elbistan earthquake. The method integrates unmanned aerial vehicle (UAV)–based topographic surveying with ground-penetrating radar (GPR) profiling across an earthquake surface rupture site. UAV surveys yielded high-resolution topography that reveals multiple surface-rupture strands. Some strands coincide with pre-existing topographic scarps, whereas others cut across bedrock highs. We then acquired three GPR profiles near the scarped area: two profiles crossing two parallel surface-rupture strands, and one profile oriented parallel to and between them (Figure 1). The GPR data image multiple pre-event offsets and deformation within late Quaternary sediments, indicating that the Yeşilyurt Fault at the study site has hosted multiple large earthquakes prior to the 2023 Elbistan event. Together, the UAV and GPR results suggest that the Yeşilyurt Fault at this location is a previously unidentified active fault segment rather than a newly generated fault. This study demonstrates the utility of combining UAV-based topography and GPR imaging for evaluating the activity and rupture history of “hidden” faults that emerge during large earthquakes.
Figure 1. (a) Surface ruptures of the 2023 Mw 7.6 Elbistan earthquake superposed on the UAV DSM-based topographic map. Surface ruptures are constrained based on our field investigation and the UAV-derived DSM and orthoimage. The black rectangle shows the location of the study site (b and c). (b) The topographic map shows the study site and the locations of the GPR lines. Arrows show the GPR survey directions. (c) Geological interpretation of (b).
How to cite: Su, P., Zabcı, C., Sançar, T., Sun, X., He, H., Zhang, Y., and Zhang, Y.: Ground Penetrating Radar Survey Revealing Pre-Event Earthquakes on the 6 February 2023 Mw 7.5 Elbistan Earthquake Surface Rupture, Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4896, https://doi.org/10.5194/egusphere-egu26-4896, 2026.
Coseismic displacement and deformation patterns near seismic rupture zones are crucial for understanding earthquake rupture processes, fault behaviors, and the relationship between active faults and topographic features. Recent advances in sub-meter accuracy digital terrain data derived from high-resolution optical satellite stereo imagery have provided new geodetic approaches for differential topography studies, including three-dimensional coseismic surface displacement field acquisition. This study generated pre- and post-earthquake topographic point cloud data (average point density: 1.2 points/m²) using GF-7 satellite stereo imagery, and obtained a 25-meter spatial resolution three-dimensional coseismic surface displacement field in the near-fault area of the 2025 Dingri, Tibet Mw7.1 earthquake through a window-based (50-meter window size) Iterative Closest Point (ICP) algorithm. The results reveal that the surface rupture of the Dingri earthquake was dominated by vertical displacement with insignificant horizontal motion, consistent with the focal mechanism solutions and field investigations of the rupture zone. The vertical displacement distribution extracted from ICP displacement field exhibits a "high central section with decreasing values northward and southward" pattern, reaching a maximum vertical displacement of ~2.5 m near the central Nixiacuo area, decaying to ~1.2 m northward and ~0.5 m southward. Compared with field measurements, ICP-derived vertical displacements generally exceed field observations, indicating that surface dislocation markers only reflect the minimum coseismic displacement along the rupture zone. The ICP method quantifies cumulative displacement across hundreds of meters on both sides of the rupture, providing critical constraints for studying shallow slip deficit mechanisms and facilitating future investigations of fault slip transfer processes from deep to shallow levels. This study demonstrates the unique advantages of new high-resolution optical satellites in long-term pre-seismic data accumulation, rapid post-seismic data acquisition, and comprehensive coverage of surface deformation zones. These capabilities enable timely construction of near-field 3D coseismic displacement fields, allowing differential topography techniques to measure 3D coseismic deformation in areas inaccessible for LiDAR surveys. This approach effectively compensates for limitations of conventional InSAR and sub-pixel correlation techniques near surface ruptures, where large deformation gradients or insensitivity to vertical displacements often cause measurement failures.
How to cite: Wei, Z., Ma, C., and Deng, Y.: Coseismic Surface Displacements Derived From High-Resolution GF-7 Stereogrammetric Terrain Differencing: The 2025 Tibet Dingri Mw7.1 Earthquake, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6289, https://doi.org/10.5194/egusphere-egu26-6289, 2026.
The Red River Fault (RRF) presents a significant seismological paradox: its northern segment hosts frequent large earthquakes, whereas its southern segment remains largely quiescent despite similar tectonic loading. To investigate how fault-zone structure and frictional properties govern this seismicity contrast, we sampled outcrops where mylonitic shear zones host multiple layers of cataclasite within the fault core. In the northern segment, the mylonites are dominated by quartz and feldspar, by contrast, the mylonite is hornblende rich in the southern segment. Hydrothermal friction experiments are then conducted on the sampled mylonite and cataclasite fault rocks at 100–500 °C, fluid pressures of 50–100 MPa, and confining pressures of 150–200 MPa, approximating upper-midcrustal earthquake nucleation conditions.
Our experimental results reveal a critical rheological contrast between the two segments. In the aseismic southern segment, the fault core cataclasites exhibit a transition to velocity weakening at intermediate temperatures; however, the surrounding mylonitic host rocks display stable velocity strengthening behavior across nearly the entire temperature range. Conversely, mylonitic host rocks from the seismically active northern segment exhibit unstable velocity weakening behavior over a wide temperature range of 150–500°C. Based on the architecture of the fault and numerical modeling, we propose that the frictional stability of the surrounding mylonitic rock acts as a rheological gate for earthquake propagation. In the south, although nucleation may initiate within the relatively weak and velocity-weakening cataclasite (μ=0.53-0.62), the contrasting stable response of the surrounding mylonite acts as a damper, arresting rupture and suppressing large events. In the north, the unstable velocity-weakening nature of the host rock promotes a "runaway" rupture process, amplifying nucleation events into large earthquakes. These results challenge models focused only on single fault rock properties, highlighting how host-rock rheology modulates seismic hazard along major continental faults.
How to cite: Yang, Z., Zhang, L., Barbot, S., and Duan, Q.: Host-Rock Rheology Controls Seismicity Segmentation along the Red River Fault, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6526, https://doi.org/10.5194/egusphere-egu26-6526, 2026.
The central Ionian Islands exhibit the highest seismogenic potential in the central Mediterranean and have therefore been extensively studied to mitigate the seismic risk. Despite numerous investigations over recent decades, the actual seismic hazard affecting the islands remains incompletely constrained.
The work was carried out within the framework of the internship project “Hazard assessment combining geological, geophysical and seismological data offshore Ionian Islands, Greece”, and aims to investigate the location and geometry of the main faults in the offshore area between Zakynthos and Cephalonia and to correlate offshore faults segments identified in the marine domain with their onshore counterparts. Particular attention is given to the Ionian Thrust and to the fault that was responsible for the destructive August 1953 earthquake that devastated Cephalonia Island.
We analyzed a comprehensive geophysical dataset acquired during two marine geophysical surveys: IONIANS 2022 (CNR project) and POSEIDON 2023 (Eurofleet+ project). The dataset includes three high-resolution and two high-penetration multichannel seismic profiles, several kilometers of TOPAS sub-bottom profiles and high-resolution swath bathymetry. Seismic interpretation allowed us to map the Ionian Thrust from south of Zakynthos to Cephalonia and its intersection with the main trace of the Cephalonia strike-slip fault. In the offshore domain, the Ionian Thrust is expressed as west-verging anticline with local transcurrent component. Moreover, in the narrow marine passage between Cephalonia and Zakynthos, we identified a west-verging anticline with transcurrent component which aligns well with the hypothesized epicenter of the 1953 earthquake.
Our interpretations were integrated and compared with existing geological and geophysical models from the literature, enabling the identification of the offshore continuations of fault systems responsible for several historical and instrumental seismic events. By further integrating offshore data with the onshore geology of both islands, we achieved a robust land–sea correlation of the dominant tectonic structure in the area, namely the Ionian Thrust.
Finally, the combined analysis of newly-identified tectonic structures and regional seismicity, allowed us to draw the position and trend of the seismogenic fault source of the 1953 earthquake as well as the active segments of the Ionian Thrust. These new findings strongly improve our understanding of the tectonic framework of the marine area surrounding the central Ionian Islands and provide crucial input for future seismic hazard modeling and risk assessment in this area of the western Hellenic Arc.
How to cite: Puisne, M., Loreto, M. F., Ranero, C. R., Ganas, A., Ferrante, V., and Nomikou, P.: Sea-Land correlation of the main seismogenic faults shaping the central Ionian Islands, Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7442, https://doi.org/10.5194/egusphere-egu26-7442, 2026.
The region of the Aegean Sea, shaped by the subduction of the African plate beneath the Eurasian plate with the intervening Aegean microplate, is one of the most actively deforming areas in the Mediterranean. This system is characterized by strong lateral variations in its tectonic style, where extension in the back arc region has created rifts like the Rifts of Corinth and Evia; volcanic activity in the Southern Aegean Active Volcanic Arc is associated with active subduction along the Hellenic trench; the lateral ocean–continent transition along the Western Hellenic subduction lead to strain partitioning and the formation of Kefalonia strike slip zone, and major strike-slip deformation accommodated by the North Anatolian transform fault associated with west ward motion of Anatolia. Past and ongoing tectonics resulted in a highly heterogeneous lithospheric configuration, which controls the degree of deformation and its localization as reflected by variations in physical properties of the lithosphere.
We present an updated 3D geological model of the Aegean Sea and Hellenic subduction system, which we use to map first-order rheological contrasts in the lithosphere, being constrained by available seismic and seismological observations and by 3D gravity modelling. The model integrates several datasets, including the EPcrust crustal model, available seismic sections, mantle and crustal tomographies, and observed gravity anomalies. The S- and P- wave velocities of the tomographic datasets were converted to densities in order to consistently map 3D density variations in the lithospheric mantle and the crust.
Preliminary gravity modelling results show a good match with observed gravity, fitting regional trends in gravity anomalies across the study area. In a second stage, we carried out a sensitivity analysis to investigate in more details the effect of lithospheric density variations. Specifically, we focused on the transitional domain between the Moho and the upper mantle, where uncertainties in converting seismic velocities to density remain significant.
The model provides new constraints on density variations in the lithosphere, which, especially with the derived strength and temperature contrasts, help to better understand how deformation localizes in the Aegean region.
How to cite: Vatai, Z., Scheck-Wenderoth, M., Bott, J., Cacace, M., and Huismans, R. S.: Lithospheric Density Structure of the Aegean Region Constrained by 3D Gravity Modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7615, https://doi.org/10.5194/egusphere-egu26-7615, 2026.
The marine area between Chios, Ikaria and Samos islands occupies a key position within the Central Aegean extensional domain, encompassing the offshore segments of several active fault systems, including those responsible for the 30 October 2020 Mw 7.0 Samos earthquake. Despite the significant seismic and tsunami hazards, the subsurface stratigraphic architecture and three-dimensional geometry of active faults in this region are remain poorly constrained. The aim of this study is to present preliminary results of an integrated seismic stratigraphic and structural interpretation based on five multichannel seismic reflection profiles (total length ~364 km) obtained by MTA and reprocessed into SEG-Y format. The study also includes previously published seismic profiles reinterpreted within a tectonostratigraphic framework, as well as high-resolution bathymetric data compiled from SHOD and international sources.
The seismic profiles indicate the presence of a prominent acoustic basement, overlain by a thick Neogene-Quaternary sedimentary succession, characterised by laterally continuous to locally progradational reflector packages. The basement surface exhibits significant relief, featuring a complex network of high-angle normal faults that form a system of asymmetric basins and structural highs. Above the basement, the sedimentary architecture displays a variety of reflector geometries, including parallel, divergent and clinoform patterns. These patterns are indicative of deltaic or slope-related depositional architectures, particularly in the western part of the study area.
Both newly processed and literature seismic sections demonstrate a predominant orientation of NW-SE and NE-SW-striking faults, which is consistent with the present-day Aegean extensional regime. Several of these faults clearly intersect with the shallowest reflectors, thereby indicating Quaternary to potentially present-day activity. The North Ikaria Basin, in particular, exhibits notable fault-controlled subsidence, expressed by thickened sedimentary packages and cumulative vertical displacements. These observations suggest the presence of long-lived tectonic control on basin development.
The three-dimensional correlation of fault planes and key stratigraphic reflectors enables the characterization of the geometry of the basin-bounding structures, and the evaluation of their possible kinematic linkage with the onshore fault systems of western Anatolia and the eastern Aegean islands. The integrated interpretation highlights the role of segmented normal fault systems in controlling basin architecture, sediment distribution patterns and accommodation space during the Neogene-Quaternary evolution of the Central Aegean back-arc domain.
These results provide a first-order seismic stratigraphic and structural framework for the offshore region between Chios, Ikaria and Samos. This framework is the result of the combination of newly reprocessed and legacy seismic datasets, which have been evaluated within a consistent tectonic context. The ongoing analysis will form the basis for detailed fault mapping, thickness distribution and kinematic reconstructions, and will contribute to a better understanding of the relationship between active crustal deformation and seismic hazard in the eastern Aegean region.
How to cite: Elitez, İ.: Active Tectonic Framework and Seismic Stratigraphy of the Central Aegean: The Chios-Ikaria-Samos Marine Area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8235, https://doi.org/10.5194/egusphere-egu26-8235, 2026.
Modeling crustal deformation induced by fault slip is a fundamental problem in structural geology and seismology. However, the challenges of data sparsity and spatial discontinuity impose significant limitations on conventional forward and inverse methods, often resulting in low computational efficiency and limited accuracy. Although AI-based approaches such as Physics-Informed Neural Networks (PINNs) and Physics-Encoded Finite Element Networks (PEFEN) offer new solutions for sparse-data problems governed by physical laws, their underlying assumption of spatial continuity conflicts with the inherent displacement discontinuities of fault-slip fields. To address this limitation, we propose a novel method—the Split-Node Physics-Encoded Finite Element Network (SN-PEFEN)—which integrates the node-splitting mechanism into the PEFEN framework. By explicitly encoding spatial discontinuities into the nodal topology during mesh preprocessing, SN-PEFEN not only overcomes the theoretical limitations of existing PEFEN models in handling discontinuous fields but also maintains the physical consistency. We apply SN-PEFEN to perform forward and inverse modeling of deformation fields induced by complex fault slip in both 2D and 3D heterogeneous media. For a model with over one million degrees of freedom, the forward simulation achieves over 40× speedup compared to traditional FEM (~1,800s vs. 42s), while maintaining comparable accuracy. In inverse modeling, the solution converges within only 100 iterations, with a total runtime of approximately 2,000 s, demonstrating high computational efficiency. This method establishes a new high-efficiency paradigm for analyzing complex discontinuous deformation in geomechanics, offering promising applications in multi-fault system analysis and fault-slip inversion. Furthermore, SN-PEFEN facilitates rapid, physics-based assessments for emergency seismic response and disaster management, while laying the groundwork for next-generation data-driven regional earthquake early warning systems.
How to cite: Tao, W. and Yang, X.: Split-Node Physics-Encoded Finite-Element Network for Forward and Inverse Modeling of Fault-Slip-Induced Discontinuous Deformation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8731, https://doi.org/10.5194/egusphere-egu26-8731, 2026.
The Xiadian Fault is a major active fault along the northern margin of the North China Plain and is widely considered to be closely associated with the 1679 Sanhe–Pinggu M8.0 earthquake. Compared with its central and southern segments, the northern segment of the Xiadian Fault—particularly within the Pinggu area—remains poorly constrained in terms of its spatial distribution, strike variations, and geometric characteristics, which hampers a comprehensive understanding of its tectonic role and seismic hazard implications. In this region, thick Quaternary deposits extensively cover the surface, and the fault is predominantly concealed, resulting in a lack of clear and continuous surface expressions and increased uncertainty in fault identification and precise location.
In this study, the northern segment of the Xiadian Fault is investigated based on a systematic analysis of regional geological and tectonic settings, combined with multiple shallow seismic reflection profiles oriented in different directions. The seismic responses of the fault within Quaternary strata are analyzed to constrain its planar location, strike changes, and spatial continuity in the Pinggu area. The geometric features and possible segmentation of the fault are further examined, and the tectonic mechanisms responsible for observed strike deflections are discussed in the context of the regional stress field and inherited basement structures. The results provide new geophysical constraints on the detailed geometry of the northern segment of the Xiadian Fault and contribute to an improved understanding of seismotectonics and seismic hazard assessment along the northern margin of the North China Plain.
How to cite: Sun, J.: Spatial Distribution and Geometric Characteristics of the Northern Segment of the Xiadian Fault, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9590, https://doi.org/10.5194/egusphere-egu26-9590, 2026.
The Yedisu Segment is one of the most significant seismic gaps of the North Anatolian Fault Zone (NAFZ), following the segments located near Istanbul. This segment is approximately 80 km long and has remained seismically quiet for about 242 years. It has the potential to generate an earthquake magnitude of greater than Mw 7. The Tercan and Nazımiye dextral faults are located in the vicinity of the Yedisu Segment and exhibit similar strikes of approximately N70–75°W. In this study, slip rates and locking depths of the Yedisu Segment and its neighboring Tercan and Nazımiye faults are estimated by inverting GNSS-derived Eurasia-fixed velocity fields using elastic half-space dislocation models. Velocities from Turkish Real-Time Kinematic GNSS Network (CORS-TR, including a few older stations), Turkish National Fundamental GPS Network (TNFGN), and previously published regional GNSS networks are used, and the inversions are performed using fault-parallel velocity components while accounting for differences in fault strike. Two different forms of elastic half-space dislocation model are tested for the Yedisu Segment: (i) symmetric and (ii) asymmetric fault-slip behavior. The symmetric model yields a Yedisu slip rate of approximately 18.7 mm/yr, while the Nazımiye and Tercan faults contribute only minor deformation to the regional velocity field. The asymmetric model conversely discloses a difference between the south- and north-side of the Yedisu Segment, with slip rates of about 6.5 and 11.9 mm/yr, respectively. The fault slip rate asymmetry correspondes to a ratio of 1.83. The asymmetric model explicits a significantly better fit to the GNSS velocity field than the symmetric approach. Assuming a long-term average slip rate of 18.4 mm/yr, the Yedisu Segment has accumulated approximately 4.45 m of slip deficit over the past 242 years, consistent with the potential for a large, destructive earthquake. These results indicate that the Yedisu seismic gap is highlighting its critical importance for seismic hazard assessment in eastern Türkiye. This research is supported by the TÜBİTAK project No. 124Y204.
Keywords: North Anatolian Fault, Yedisu Segment, GNSS, Fault slip asymmetry, Seismic gap
How to cite: Tecel, O., Duman, H., Poyraz, B., Poyraz, F., Hastaoglu, K. O., Kocbulut, F., Gul, Y., and Kapicioglu, A.: Slip asymmetry of the Yedisu Segment of the North Anatolian Fault from GPS velocity fields, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10261, https://doi.org/10.5194/egusphere-egu26-10261, 2026.
Tectonically complex areas can give rise to large heterogeneity in source properties, which have a direct impact on observed ground motion. On November 12, 2025, the Eastern Mediterranean island of Cyprus experienced two M5+ earthquakes just 5 hours apart. Initial locations by the Cyprus Geological Survey Department put the two epicenters within 2 km of each other, but 10 km apart in depth. Moment tensor inversions from long-period waveform data show the first event had a magnitude around Mw5.1, with the second event measured at Mw5.4. However, observed peak ground velocity and acceleration amplitudes were almost indistinguishable between the two events. In this work, we revisit these observations and try to reconcile them using joint analyses of earthquake relocations, moment tensors, observed ground motions, and finite fault modeling. We relocate the events using a non-linear, probabilistic location algorithm and model point source moment tensors, showing the events occurred close in space and at a very similar depth. We derive relative moment rate functions (MRFs) for the two events via empirical Green’s function deconvolution. We find the Mw5.1 shows simple, sub-second duration MRFs. On the other hand, the Mw5.4 exhibits multi-peaked, complex MRFs with pulse durations up to 4 times longer than those of the Mw5.1. This suggests a simple, fast rupture in the first event contrasting with a likely slow, sluggish, and complex rupture in the second. We run finite fault modeling to reconcile observed ground shaking with source properties. Finally, we interpret the ruptures in the context of the highly complex tectonics of the Cyprus arc.
How to cite: Marcou, S., Taira, T., Dimitriadis, I., Papadimitriou, N., and Pilidou, S.: Neighboring but Different: Linking Ground Motions to Source Properties of the November 2025 Cyprus Doublet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10612, https://doi.org/10.5194/egusphere-egu26-10612, 2026.
The double earthquakes (Mw 7.8 and Mw 7.5) that occurred in eastern Turkey on February 6, 2023, caused heavy casualties and economic losses, and significantly altered the regional tectonic stress environment. The Malatya Fault, as a key active structure in the area, has experienced a 2,500-year gap without surface-rupturing large earthquakes, raising concerns about its potential seismic hazard. This study, based on high-precision relocated aftershock data from the Turkish double earthquakes and multi-source geological and geophysical data, precisely constructed the three-dimensional geometric structure of the Malatya Fault and the fault that generated the earthquakes. On this basis, combined with geodetic data constraints, a three-dimensional viscoelastic finite element model of the eastern Turkey region was established. This study aims to quantitatively calculate the coseismic and postseismic viscoelastic relaxation effects of the double earthquakes on the Coulomb stress loading characteristics of the Malatya Fault through numerical simulation methods, and analyze the spatiotemporal distribution patterns of stress along the fault strike and at depth. By integrating the fault's own seismogenic background and tectonic loading environment, a comprehensive assessment of the current seismic hazard of the Malatya Fault is conducted, providing a scientific basis for understanding the stress interaction between faults and regional earthquake prevention and disaster reduction.
How to cite: Li, H.: Numerical Simulation Study on Seismic Hazard of the Malatya Fault, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11516, https://doi.org/10.5194/egusphere-egu26-11516, 2026.
The Main Marmara Fault beneath the Marmara Sea constitutes a major seismic gap capable of generating a large earthquake, posing a serious hazard to the region and its surroundings. Consequently, detailed characterization of seismicity and its relationship to fault-zone deformation is essential. One of the primary objectives of this study is to compile a seismicity database for the Marmara Sea covering the period 2014–2016, based primarily on data recorded by ocean-bottom seismometers.
The detected and relocated seismicity reveals distinct spatial and depth-dependent patterns among the Marmara basins. The Tekirdağ Basin is characterized by diffuse seismicity at depths of approximately 7–18 km. In contrast, the Central Basin exhibits a high rate of microearthquake activity between 3 and 15 km depth. The Kumburgaz Basin and the western part of the Çınarcık Basin, show sparse seismicity within depth ranges of 5–19 km and 3–18 km, respectively.
Previously identified repeating earthquakes were searched using a template-matching approach applied to continuous seismic waveforms spanning a larger time frame of 2008–2021. Clusters of highly correlated earthquakes that occur closely in time or partially overlap are classified as near-repeating events. The Central Basin displays clear signatures of seismic creep, marked by both elevated seismicity rates and the presence of nine near-repeating earthquake clusters. Focal mechanisms of these clusters indicate dominantly strike-slip motion, consistent with the kinematics of the Main Marmara Fault. Two distinct recurrence patterns are observed among the near-repeaters, representing short-term and long-term repeating behaviors. Slip-rate estimates derived from these clusters vary spatially but are broadly comparable to geodetic slip rates.
How to cite: Basarir Basturk, N., Karabulut, H., and Meral Özel, N.: High-Resolution Seismic Analysis of the Marmara Sea: Microseismic Activity from OBS Data and Nearly-Repeating Earthquakes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13575, https://doi.org/10.5194/egusphere-egu26-13575, 2026.
Natural processes such as tectonic movements, subsidence, erosion, and hydrological variability continuously modify the coastline and basin morphology. Understanding these changes is essential for interpreting the dynamics of coastal and lacustrine systems and their responses to both gradual and sudden events. In this study, basin-scale deformation and environmental dynamics of Lake Golbasi (Adiyaman, Türkiye) were investigated within the East Anatolian Fault Zone (EAFZ), where one of the main fault branches passes directly through the Golbasi district. The Mw 7.8 Kahramanmaras earthquake that occurred on February 6, 2023, caused significant surface deformation, coastline reconfiguration, and localized subsidence, highlighting the strong coupling between tectonic activity and surface processes in the region. Time-dependent ground deformation was monitored using InSAR time-series analysis based on Sentinel-1 C-band SAR data acquired in both ascending and descending geometries and processed through the LiCSBAS framework and the ASF HyP3 cloud-based processing system, covering the period from 2021 to 2025. This temporal coverage allows the investigation of pre- and post-earthquake deformation and coastline changes, as well as their spatial and temporal relationship with the active fault system in the Golbasi Basin. The tectonic interpretation of the observed deformation features was further supported through an evaluation of the orientation and spatial position of the identified surface deformation patterns relative to mapped fault traces, post-earthquake surface ruptures, and the distribution of seismic activity. The Normalized Difference Water Index (NDWI) was applied to optical Sentinel-2 imagery to better characterize the basin’s dynamic environmental conditions and to support the interpretation of the observed deformation signals. Seasonal NDWI variations between dry and wet periods were examined to assess changes in water extent and shoreline position. This information was essential for distinguishing surface variability related to hydrological processes from deformation driven by tectonic activity. The integrated analysis reveals a complex interaction between tectonic deformation, seasonal water-level fluctuations, and basin-scale environmental dynamics. These findings improve our understanding of post-earthquake changes in the Golbasi Basin and offer explanations for how fault-controlled lakes and wetlands evolve and gradually stabilize following major seismic events.
How to cite: Uçar, A. and Ergintav, S.: InSAR Time-Series Analysis of Basin-Scale Deformation and Environmental Dynamics in the Golbasi Basin (Adiyaman, Türkiye), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17323, https://doi.org/10.5194/egusphere-egu26-17323, 2026.
Co-seismic deformation in fault damage zones manifests as a combination of localized slip and distributed deformation. Accurately quantifying the ratio between these two components is essential for understanding displacement partitioning and assessing near-fault seismic damage. Focusing on the widespread ruptures caused by the 2023 Turkey-Syria earthquake doublet (Mw 7.8 and Mw 7.6), this study utilizes optical satellite geodesy to dissect the deformation characteristics of the East Anatolian Fault Zone. We integrated high-resolution GaoFen-7 orthophotos (0.8 m) and Sentinel-2 imagery to distinguish between on-fault and off-fault deformation. Localized slip was measured by tracing displaced linear markers (e.g., roads, ridges), while the total horizontal displacement field was reconstructed using optical displacement tracking. By comparing total displacement across dense profiles against localized slip, we isolated the distributed component. Results show that for the Mw 7.8 event, 80% of displacement was localized, with 20% distributed across a 203-meter-wide zone. Similarly, the Mw 7.6 event exhibited 17% distributed deformation within a 141-meter-wide zone. Notably, we observe that the spatial heterogeneity of deformation is strongly controlled by the pre-existing geometric complexity of the fault system. These findings provide critical constraints for fault displacement hazard models.
How to cite: xi, X., li, C., li, T., and wei, Z.: Characteristics of Distributed Deformation in the 2023 Turkey Earthquake Doublet Fault Zone Revealed by Optical Geodesy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17537, https://doi.org/10.5194/egusphere-egu26-17537, 2026.
How to cite: Koçak, A., Göğüş, O. H., Bodur, Ö., and Aslan, C.: The Crucial Link Between Sedimentation and the Activity of the Pull - Apart Basins Revealed by Models and Observations Over Aegean-Anatolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20058, https://doi.org/10.5194/egusphere-egu26-20058, 2026.
Active fault mapping and fault databases are fundamental components of seismic hazard assessment, land-use planning, and disaster risk reduction in tectonically active regions. The effectiveness of such databases critically depends on their ability to integrate paleoseismological evidence, surface rupture observations, and consistent fault characterization across multiple spatial scales. Türkiye, located within the actively deforming Alpine–Himalayan orogenic belt, provides an important natural laboratory for evaluating how national-scale active fault databases can be systematically updated and improved.
The General Directorate of Mineral Research and Exploration (MTA), the national geological survey of Türkiye, has conducted active fault and paleoseismological investigations since the 1970s. These efforts led to the publication of successive editions of the Active Fault Map of Türkiye, first at a scale of 1:1.000,000 in 1992 and later updated to 1:1.250.000 in 2013 following the 1999 Gölcük (Mw 7.4) and Düzce (Mw 7.2) earthquakes. The 2013 map has since served as the primary reference for seismic hazard studies in Türkiye.
Within the framework of nationwide paleoseismology and crustal research projects, trench-based investigations had been completed by the end of 2025 on approximately 250 faults or fault segments included in the 2013 database. These studies resulted in revised fault activity classifications, updated segmentation models, and the identification of nearly 100 previously unmapped active faults. In addition, major surface-rupturing earthquakes, including the 2020 Sivrice (Mw 6.8) event and the catastrophic 2023 Kahramanmaraş doublet earthquakes (Mw 7.8 and Mw 7.6), produced more than 600 km of surface ruptures that were systematically documented and mapped by MTA.
In order to incorporate these new datasets, MTA conducted the “Revision and Improvement of the Active Fault Map of Türkiye Project” between 2022 and 2025. This project integrated paleoseismological data, detailed surface rupture mapping, and 1:25.000-scale active fault maps into a unified digital Active Fault Database. The resulting 1:1,000,000-scale Active Fault Map of Türkiye was generated through the digitization and integration of high-resolution fault data.
This contribution presents the methodological framework, data structure, and revision strategy of the Active Fault Database of Türkiye, emphasizing approaches that are applicable to other tectonically active regions worldwide. The results demonstrate how integrating paleoseismology, earthquake surface ruptures, and multi-scale fault mapping significantly enhances the reliability of active fault databases, with direct implications for seismic hazard assessment, urban resilience, and disaster risk mitigation in regions affected by distributed deformation.
How to cite: Elmacı, H., Kürçer, A., Altuntaş, G., Aydoğan, H., Yüce, A. A., Avcı, H. O., Karayazı, O., Bayrak, A., Öztürker, A. R., Çal, Ç., Yalvaç, O., Güven, C., and Özalp, S.: The Active Fault Database of Türkiye: Framework, Methodology, and Ongoing Revisions by the General Directorate of Mineral Research and Exploration (MTA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20721, https://doi.org/10.5194/egusphere-egu26-20721, 2026.
Recent studies have shown that large earthquakes can induce deformation at distances significantly greater than those predicted by simple elastic half-space models. This observation indicates that regional-scale effects must be considered when assessing post-earthquake deformation and seismic hazard. Several studies have demonstrated that the 6 February 2023 Kahramanmaraş earthquake doublet (Mw 7.8 and Mw 7.6) affected distant regions in addition to the immediately ruptured faults.
Within the scope of our project, supported by TÜBİTAK 1001 (Project No. 123Y350), we investigate the current fault activity and seismic hazard of fault segments located north of the 2020 Mw 6.8 Sivrice earthquake and the 2023 Mw 7.8–7.6 Kahramanmaraş earthquakes. Our approach integrates multidisciplinary datasets, including seismology, geodesy (GNSS, InSAR, and creepmeters), and geology (morphometric analyses). The study area comprises the East Anatolian Fault (EAF)–Palu segment, the North Anatolian Fault (NAF)–Yedisu segment, and the Karlıova Triple Junction (KTJ).
Following the 2020 Mw 6.8 Sivrice earthquake, seismicity increased along several sections of the EAF. Initially, aftershocks were concentrated within the rupture zone and subsequently migrated southwestward, while no significant increase in seismicity was observed along the Palu segment to the north. Approximately three years later, the Kahramanmaraş earthquake sequence (Mw 7.8 and Mw 7.6) occurred on 6 February 2023, after which seismic activity expanded over a broad region along the EAF. Compared to the ruptured areas and their immediate surroundings, seismicity remained relatively sparse along the northern sections of the EAF, where our study area is located.
The Palu segment lies adjacent to the NE the Sivrice earthquake rupture zone and forms part of the EAF, whereas the Yedisu segment, located on the NAF, is characterized by a long-term slip deficit and is considered a seismic gap. The Karlıova Triple Junction represents the intersection of the North and East Anatolian faults and exhibits a complex faulting system resulting from active continental collision. Each of these fault segments displays distinct kinematic characteristics and has been affected by the 2020 and 2023 earthquakes to varying degrees.
The current seismicity distribution within the study area (Palu, Yedisu, and KTJ) indicates that earthquake clusters observed prior to these large events remain active, with no anomalous seismic behavior identified to date. Despite the relatively low level of seismicity along the Palu segment compared to the main rupture zones, geodetic observations suggest that its well-known creep velocity has accelerated following the 2020 and 2023 earthquakes. In addition, we investigate the relationship between long-term and present-day geodetic deformation rates, morphological indicators, and slip deficits along active fault branches using continuous and campaign GNSS measurements together with InSAR data. These multidisciplinary datasets, currently under preparation, will be integrated intofault interaction modeling and seismic hazard assessments for the region at the conclusion of the project.
How to cite: Eskikoy, F., Ergintav, S., Sancar, T., Ozdemir, A., Cakir, Z., Tan, O., Cakmak, R., Ayruk, E. T., Turgut, M., Beytut, B. B., and Dogan, U.: Highlights of current activity along EAF-Palu, NAF-Yedisu segments and Karlıova Triple Junction:Following the 2020 (Mw 6.8 Sivrice) and 2023 (Mw 7.8-7.6 Kahramanmaras) earthquakes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18830, https://doi.org/10.5194/egusphere-egu26-18830, 2026.
