TS3.10 | Active Tectonics and Geodynamics of Eastern Mediterranean
Active Tectonics and Geodynamics of Eastern Mediterranean
Co-organized by GD9/SM1
Convener: A. Ozgun Konca | Co-conveners: Seda Özarpacı, Bernhard Grasemann, Sylvain Barbot
Orals
| Fri, 28 Apr, 08:30–11:55 (CEST)
 
Room K1
Posters on site
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
Hall X2
Posters virtual
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
vHall TS/EMRP
Orals |
Fri, 08:30
Thu, 16:15
Thu, 16:15
The Eastern Mediterranean is an actively deforming region where three major tectonic plates interact: the African, the Arabian and the Eurasian plates. The Cenozoic geodynamic framework of the Eastern Mediterranean region consists of subduction, collision, strike-slip kinematics, extrusion of crustal blocks and slab deformation.

This session focuses on three aspects of the Eastern Mediterranean geodynamics:
(1) Which geodynamic mechanisms define the key active structures and how do they operate?
(2) How is surface deformation being accommodated over a range of temporal and spatial scales? How individual earthquakes accrue on faults to account for their long-term kinematics? Which is the impact of deep-seated processes on surface deformation?
(3) How did the geodynamic evolution through the Cenozoic lead to present day tectonic deformation?

We welcome contributions from a wide range of disciplines including, but not limited to, neotectonics, seismology, tectonic geodesy (e.g. GNSS, InSAR), paleoseismology, tectonic geomorphology, remote sensing, structural geology, and geodynamic modeling.

We strongly encourage the contribution of early career researchers.

Orals: Fri, 28 Apr | Room K1

Chairpersons: A. Ozgun Konca, Bernhard Grasemann
08:30–08:40
|
EGU23-96
|
ECS
|
On-site presentation
Thomas Merry, Ian Bastow, David Green, Stuart Nippress, Charlie Peach, Rebecca Bell, Sylvana Pilidou, Iordanis Dimitriadis, and Freddie Ugo

Cyprus sits at the plate boundary between Anatolia in the north and Africa in the south, at a transition from oceanic subduction in the west to continental strike-slip and collision tectonics in the east. The nature of the plate boundary at Cyprus has been historically controversial and poorly understood, in part due to a lack of constraints on local seismicity. Ongoing subduction of either oceanic or continental African lithosphere is argued, with some invoking subduction of the Eratosthenes Seamount, a continental fragment to the south of Cyprus rising 2km above the sea floor, as a driver of uplift in Cyprus. At the centre and highest point of the Troodos ophiolite, which dominates the island, is the Mt Olympus mantle sequence, an outcrop of heavily serpentinised peridotite that is associated with a localised gravity low and proposed to be the top of a rising serpentinite diapir. Geophysical constraints to test these hypotheses at depth are lacking. 

 

We analyse data from a two-year deployment of five broadband seismometers along with the existing permanent network to create a new earthquake catalogue for Cyprus. We use our catalogue to constrain the first formalised 1-D velocity model for the island, improving earthquake locations. Earthquake hypocentres clearly delineate a northward-dipping African slab beneath Cyprus at 20-60 km depth. The most seismically active part of the island is at 15-20 km depth beneath the southern edge of the ophiolite, approximately the expected depth to the plate interface; thrust faulting focal mechanisms here are consistent with ongoing subduction. Hypocentral depths suggest a topography of the slab top, with the shallowest depths in the centre of the island, coincident with the greatest uplift in the overlying plate, supporting hypotheses of uplift driven by subduction of the Eratosthenes Seamount. A lack of seismicity in a 20km-wide zone at this ‘peak’ coincides with the outcropping Mt Olympus mantle sequence, and may be associated with the deep root of the proposed serpentinite diapir. 

How to cite: Merry, T., Bastow, I., Green, D., Nippress, S., Peach, C., Bell, R., Pilidou, S., Dimitriadis, I., and Ugo, F.: Subduction, uplift and serpentinite in Cyprus: insights from seismicity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-96, https://doi.org/10.5194/egusphere-egu23-96, 2023.

08:40–08:50
|
EGU23-12210
|
On-site presentation
Konstantinos Soukis, Stelios Lozios, Emmanuel Vasilakis, Varvara Antoniou, and Sofia Laskari

The present-day geotectonic regime of Crete Island is mainly controlled by the processes occurring along the seismically active Hellenic subduction zone, e.g., the fast convergence between Africa - Eurasian plates (at a rate of 36 mm/yr) and the simultaneous SSW-ward retreat of the subducting slab. The result is a large south-facing orogenic wedge extending from the southern coast of Crete up to the Hellenic subduction trench to the South. Contractional structures (thrusts, folds, and duplexes) have formed in the deeper parts of the wedge and caused the thickening of the crust. This has led to substantial regional uplift and extension of the upper part of the wedge. Hence, two significant arc-parallel and arc-normal sets of active normal faults crosscut the Cretan mainland, affecting the entire alpine nappe pile. These faults have created a characteristic basin and range topography expressed through impressive E-ESE and N-NNE horst and graben structures bounded by fault zones with segments ranging from 5 to more than 20 km.

 

Detailed fault mapping of the Mirabello Gulf – Ierapetra Basin depression revealed a dominant NNE-SSW fault system, occupying the central and northern part, and a subordinate E-W to ESE-WNW system, observed mainly along the southern coastal zone. In the ESE margin, the deformation is localized mainly along the 30 km long NNE-SSW Kavousi – Ieraptera fault zone. On the other hand, in the WNW margin, the deformation is distributed in a larger population of relatively minor faults, organizing in more complex second-order horst and graben structures. In the southern part of the Ierapetra Basin, the E-W to ESE-WSW faults are significantly less and concern 2-3 specific zones. Specific morphological structures such as the remarkable range high, the deep V-shaped gorges, the large scree thickness, and the prominent post-glacial fault scarps produced along the basin margins indicate the intensive activity of these faults during the Quaternary. The NNE-SSW fault system seems to be younger and more active, given that i) intersects the E-W or ESE-WNW faults of the southern part, ii) produces significant fault scarps and polished fault surfaces in the cemented scree along the fault zone, and iii) kinematically is compatible with the recent and present-day focal mechanisms (e.g., the 2021 Arkalochori earthquakes). In conclusion, the Ierapetra Basin has formed and developed through an overall E-W extension parallel to the present-day geometry of the arc.

How to cite: Soukis, K., Lozios, S., Vasilakis, E., Antoniou, V., and Laskari, S.: Active extensional tectonics along the Mirabello Gulf – Ierapetra Basin depression (Eastern Crete, Greece), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12210, https://doi.org/10.5194/egusphere-egu23-12210, 2023.

08:50–09:00
|
EGU23-10446
|
On-site presentation
A Deeper Look Into the 2021 Tyrnavos Earthquake Sequence(TES) Reveals Coseismic Breaching of an UnrecognizedLarge-Scale Fault Relay Zone in Continental Greece
(withdrawn)
Vasiliki Mouslopoulou, Henriette Sudhaus, Kostas konstantinou, John Begg, Vasso Saltogianni, Benjamin Männel, Ratri Antinisari, and Onno Oncken
09:00–09:20
|
EGU23-17079
|
solicited
|
Highlight
|
On-site presentation
Vincent Roche, Laurent Jolivet, Stéphane Scaillet, Johann Tuduri, Vincent Bouchot, Laurent Guillou-Frottier, and Erdin Bozkurt

During the Cenozoic, the Menderes Massif (western Turkey) records several tectonic and thermal events from subduction to collision, then back-arc extension. But the detailed timing of the succession of different P-T regimes and deformation until today remains debated. To address this, we targeted the main shear zones, providing for the first time a full picture of the 40Ar/39Ar system across the massif. This approach is combined with Tmax, and P-T estimates tied to kinematic-structural data. Extensive sampling along the large top-S Selimiye shear zone allows constraining the deformation at least between 44 and 33 Ma. This shear zone acted as a thrust and was active under HT-MP (530 - 590 °C and 8.5 - 10 kbar). Conversely, the top-S South Menderes Detachment System is associated with a younging of 40Ar/39Ar ages related to exhumation and strain localization during the Late Oligo-Miocene in the Central Menderes Massif. The Bozdağ top-S shear zone then allowed the exhumation of the Bayındır nappe at ~ 21 Ma from high-temperature metamorphic conditions (590 °C). Based on these new elements, we propose for the first time a detailed scenario of the Menderes Massif evolution from the Late Cretaceous to the Present. We finally discuss why the Menderes Massif belongs currently to the regions with the highest geothermal potential in the world. We propose that geothermal activity here is not of magmatic origin but rather associated with active extensional tectonics (detachments) related to the Aegean slab dynamics (i.e., slab retreat and tearing).

How to cite: Roche, V., Jolivet, L., Scaillet, S., Tuduri, J., Bouchot, V., Guillou-Frottier, L., and Bozkurt, E.: Sequential development of shear zones in a Metamorphic Core Complex: cause and consequences in the Menderes Massif (Western Turkey), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17079, https://doi.org/10.5194/egusphere-egu23-17079, 2023.

09:20–09:30
|
EGU23-4723
|
ECS
|
On-site presentation
Sonia Yeung, Marnie Forster, Hielke Jelsma, Adam Simmons, Wim Spakman, and Gordon Lister

We present a new regional three-dimensional (3D) slab reconstruction of the Eastern Mediterranean Basin utilising the UU-P07 global tomography model and two earthquake data packages (GCMT and ISC) to produce 3D slab models to a depth of 2900 km. The model data are permissive of the presence of a south-eastward-propagating horizontal tear in the Aegean slab beneath the Rhodope Massif in the Balkanides extending towards the Thermaic Gulf. Alternatively: i) the local pattern of reduced amplitudes at ~ 200km depth could also reflect a different type of lithosphere; and/ or ii) tearing might have been preceded by down-dip stretching, resulting in abrupt thinning of the lithosphere in the extended zone.

Further to the southeast, beneath the Peloponnese and Crete, the model data support the existence of multiple subduction-transform (or STEP) faults. The subduction–transforms have since themselves begun to founder, and to roll back towards the southeast.  Even further east, beneath Cyprus, the model data appears to support the existence of yet another STEP fault, linking the slab to the east flank of the Arabia indenter.  

The 3D geometry of the subducted slabs demonstrates ‘lithological steps’ that formed as the lithosphere tore and bent while descending. Previous 3D reconstructions of the region’s deep lithospheric geometry confirmed the presence of fragmented segments but details on: i) the vertical extent of the descended slabs; and ii) the correlation between surface deformation structure and geometry at depth had yet to be established. In order to allow such a correlation, the 3D model was floated [or returned to the planet surface] utilizing a wire mesh with a Delaunay tessellation, using the program Pplates. This enabled area-balancing and therefore a more accurate approximation to the areal extent of the slabs prior to their subduction. The floated slab(s) can be incorporated in a 2D+time tectonic reconstruction to provide additional constraints not available using surface geology. The inferred tears correlate with surface structures such as the Strabo and Pliny trenches between the Hellenic Arc (Aegean Trench) and the Cyprian Trench near the Cyprus Arc, as well as with the seaward extent of the East Anatolian Fault separating the Cyprus Arc and the Arabian indenter. Such correlations between surface and deep lithospheric structures have four-dimensional (4D) implications for episodic closure of the West Tethys suture from its Mesozoic onset, through the tectonically active Tertiary to the present-day.

How to cite: Yeung, S., Forster, M., Jelsma, H., Simmons, A., Spakman, W., and Lister, G.: New 3D models for the subducted lithosphere of the Eastern Mediterranean Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4723, https://doi.org/10.5194/egusphere-egu23-4723, 2023.

09:30–09:40
|
EGU23-8525
|
ECS
|
On-site presentation
Varvara Tsironi, Athanassios Ganas, Sotiris Valkaniotis, Vassiliki Kouskouna, Ioannis Kassaras, Efthimios Sokos, and Ioannis Koukouvelas

We present new geodetic (InSAR) data (ground velocities) combined with GNSS data over the Paliki Peninsula, western Cephalonia, Greece. Paliki Peninsula suffers from strong, frequent earthquakes due to its proximity to the Cephalonia Transform Fault (CTF). The CTF, a 140 km long, east-dipping dextral strike-slip fault, accommodates the relative motion between the Apulian (Africa) and Aegean (Eurasia) lithospheric plates. The most recent earthquakes of Paliki include two events during early 2014 (Ganas et al. 2015); which occurred on 26 January 2014 13:55 UTC (Mw=6.0) and 3 February 2014 03:08 UTC (Mw=5.9), respectively. Long-term monitoring of active faults through InSAR has been successfully applied in many studies so far, not only towards identifying locked or creeping sections, but also to monitor the spatial and temporal patterns of deformation of the surrounding rocks. The processing of InSAR time series analysis was held by the LiCSBAS, an open-source package. To perform an estimate of the velocity of a surface pixel through time based upon a series of displacement data, we apply an SB (small baseline) inversion on the network of interferograms, in particular we applied the N-SBAS method. Then, we transformed the ground velocities of InSAR into Eurasia-fixed reference frame using the available GNSS station velocities. The time series analysis covers the period 2016-2022. The InSAR results demonstrate that active faults onshore Paliki are oriented approximately N-S and slip with rates between 2-5 mm/yr in line-of-sight (LOS) direction. The InSAR results also show that the horizontal component of movement is dominant, therefore supporting initial evidence of the existence of right-lateral strike slip faulting onshore the peninsula. The velocity pattern of the NW part of the peninsula also reveals a possible post-seismic motion along the ruptured plane of the 3 February 2014 earthquake. In addition, the time series analysis has identified other possible active structures (both strike-slip and thrust) onshore the Paliki peninsula and across the gulf of Argostoli that are confirmed by field geological data. The coastal town of Lixouri undergoes uplift (a few mm/yr) as it observed with positive LOS values in both satellite imaging geometries. Through the East-West velocity cross-sections, we determine several velocity discontinuities (block boundaries?) which are possibly bounded by active faults and/or crustal flexure. Overall, our results indicate a complex deformation pattern onshore the Paliki peninsula.

How to cite: Tsironi, V., Ganas, A., Valkaniotis, S., Kouskouna, V., Kassaras, I., Sokos, E., and Koukouvelas, I.: Geodetic evidence for compressional interseismic deformation onshore Paliki Peninsula, Cephalonia, Greece, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8525, https://doi.org/10.5194/egusphere-egu23-8525, 2023.

09:40–09:50
|
EGU23-8603
|
On-site presentation
Rob Govers, Matthew W. Herman, Lukas van de Wiel, and Nicolai Nijholt

Plate boundary deformation zones represent a challenge in terms of understanding their underlying geodynamic drivers. Active deformation is well constrained by GNSS observations in the SW Balkans, Greece and W Turkey, and is characterized by variable extension and strike slip in an overall context of slow convergence of the Nubia plate relative to stable Eurasia. Diverse, and all potentially viable, forces and models have been proposed as the cause of the observed surface deformation, e.g., asthenospheric flow, horizontal gravitational stresses (HGSs) from lateral variations in gravitational potential energy, and rollback of regional slab fragments. We use Bayesian inference to constrain the relative contribution of the proposed driving and resistive regional forces.

 

Our models are spherical 2D finite element models representing vertical lithospheric averages. In addition to regional plate boundaries, the models include well-constrained fault zones like north and south branches of the North Anatolian Fault, Gulf of Corinth and faults bounding the Menderes Massif. Boundary conditions represent geodynamic processes: (1) far-field relative plate motions; (2) resistive fault tractions; (3) HGSs mainly from lateral variations in topography and Moho topology; (4) slab pull and trench suction at subduction zones; and (5) active asthenospheric convection. The magnitude of each of these is a parameter in a Bayesian analysis of ~100,000 models and horizontal GNSS velocities. The search yields a probability distribution of all parameter values including model error, allowing us to determine mean/median parameter values, robustly estimate parameter uncertainties, and identify tradeoffs (i.e., parameter covariances).

 

The average viscosity of the overriding plate is well resolved 4x10^22 Pa.s, which is higher than published models without faults. Westward velocities of Anatolia and significant trench suction forces from the Hellenic slab, including along the Pliny-Strabo STEP Fault, are required to reproduce the observations. Slab pull and convective tractions have a small imprint on the observed deformation of the overriding plate. HGSs are less important for fitting the regional pattern of velocities. Resistive tractions on most plate boundaries and faults are low.

How to cite: Govers, R., Herman, M. W., van de Wiel, L., and Nijholt, N.: Probabilistic Assessment of the Causes of Active Deformation in Greece, western Anatolia, and the Balkans Using Spherical Finite Element Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8603, https://doi.org/10.5194/egusphere-egu23-8603, 2023.

09:50–10:00
|
EGU23-9268
|
ECS
|
On-site presentation
Simon Bufféral, Pierre Briole, Nicolas Chamot-Rooke, and Manuel Pubellier

During the Neogene, the Aegean domain underwent intense deformation, leading to a thinning by a factor of two or more of the Alpine orogenic prism. Today, tectonic velocity gradients are still among the fastest in Europe due to the Anatolian extrusion induced by the Arabian indentation and by the Hellenic slab retreat. The present-day deformation essentially localizes in the subduction backstop. With respect to the central Aegean, which is almost stable today, this still-thick buttress has remained at a much earlier and brittle deformation stage. This is particularly the case in the ~east–west-extending External Hellenides (Southern Greece), shaped by a series of major NNW–SSE-oriented normal faults.

  • How has the crustal deformation been accommodated by the various fault systems present in the Peloponnese since the Paleogene?
  • Which of those fault systems are still active today?
  • To what extent can boundary forces such as the Hellenic slab pull be sufficient to explain this extension?

Thanks to a significant increase in the GNSS network density in the Peloponnese, we present an updated local strain field. The resulting strain confirms the ~east–west sprawl of the External Hellenides, with extension also, to a lesser extent, in the other directions. Through identifying low-angle detachments by field and satellite morpho-structural analysis, we show that this spreading has been occurring since the Pliocene, mostly by reusing décollement layers of the Alpine nappes as extensional structures. We suggest that the main high-angle normal faults existing in the Peloponnese correspond to a localization of the extension in the weakest azimuth dictated by the Alpine backbone. We propose that this surface sprawl results not only from the Hellenic slab retreat but also from the exhumation of the deep Peloponnesian stacked units, and the subsequent crustal gravity collapse.

How to cite: Bufféral, S., Briole, P., Chamot-Rooke, N., and Pubellier, M.: The sprawl of the External Hellenides: from post-Alpine collapse to present-day kinematics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9268, https://doi.org/10.5194/egusphere-egu23-9268, 2023.

10:00–10:10
|
EGU23-10733
|
ECS
|
On-site presentation
Julia Andersen, Ebru Şengül Uluocak, Oguz Göğüş, Russell Pysklywec, and Tasca Santimano

Geological and geophysical observations show instances of surface subsidence, uplift, shortening, and missing mantle lithosphere inferred as manifestations of the large-scale removal of the lower lithosphere. This process—specifically by viscous instability or lithospheric “drips” —is thought to be responsible for the removal or thinning of the lithosphere in plate hinterland settings such as: Anatolia, Tibet, Colorado Plateau and the Andes. In this study, we conduct a series of scaled, 3D analogue/laboratory experiments of modeled lithospheric instability with quantitative analyses using the high-resolution Particle Image Velocimetry (PIV) and digital photogrammetry techniques. Experimental outcomes reveal that a lithospheric drip may be either ‘symptomatic’ or ‘asymptomatic’ depending on the magnitude and style of recorded surface strain. Notably, this is controlled by the degree of coupling between the downwelling lithosphere and the overlying upper mantle lithosphere. A symptomatic drip will produce subsidence followed by uplift and thickening/shortening creating distinct ‘wrinkle-like’ structures in the upper crust. However, the ‘symptoms’ of an asymptomatic drip are subdued as it only yields subsidence or uplift, with no evidence of shortening in the upper crust. Here, we combine analogue modelling results with geological and geophysical data to demonstrate that the Konya Basin in Central Anatolia (Turkey) is one such example of an asymptomatic drip. Global Navigation Satellite System (GNSS) measurements reveal elevated vertical subsidence rates (up to 50 mm/yr) but no well-documented crustal strain or structural features such as fold-and-thrust belts. This work demonstrates that different types of lithospheric drips may exist since the Archean, and there may be instances where the mantle lithosphere is dripping with no distinct manifestations of such a process in the upper crust.

How to cite: Andersen, J., Şengül Uluocak, E., Göğüş, O., Pysklywec, R., and Santimano, T.: Asymptomatic lithospheric drip driving subsidence of Konya Basin, Central Anatolia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10733, https://doi.org/10.5194/egusphere-egu23-10733, 2023.

Coffee break
Chairpersons: Seda Özarpacı, Sylvain Barbot
10:45–10:55
|
EGU23-12258
|
ECS
|
On-site presentation
Ali Değer Özbakır, Ali Ihsan Kurt, Ayhan Cingöz, Semih Ergintav, Uğur Doğan, and Seda Özarpacı

The Anatolia–Aegean domain represents a broad plate boundary zone, with the deformation accommodated by major faults bounding quasi-low deforming units. The main characteristics of the Anatolia-Aegean deformation were identified using a GNSS-derived velocity field. Recent advancements in GNSS measurements and networks have improved the spatial resolution of the Anatolia-Aegean deformation field, however, for a better understanding of the deformation, interstation distances that are smaller than fault-locking depth and consistent data processing using a single reference system are needed. Our goal is to address this gap and produce a uniform velocity solution.

In this study, we processed the time series of 836 stations, of which 178 are published for the first time with sub-millimeter accuracy. With a period of up to 28 years, we present the most accurate velocity field with increased spatial and temporal resolution and homogeneity. We used the improved coverage of the velocity field to calculate strain accumulation on the North and East Anatolian Faults.  Modeled slip rates vary between 20 and 26 mm/yr and 9.7 and 11 mm/yr for the North and East Anatolian faults, respectively. Further analysis of the data can help better understand the kinematics of continental deformation in general, and test outstanding hypotheses about the kinematics and dynamics of the Anatolia - Aegean domain in particular.

How to cite: Özbakır, A. D., Kurt, A. I., Cingöz, A., Ergintav, S., Doğan, U., and Özarpacı, S.: A new and uniformly processed GNSS-velocity field for Turkey, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12258, https://doi.org/10.5194/egusphere-egu23-12258, 2023.

10:55–11:05
|
EGU23-15463
|
ECS
|
On-site presentation
Jakub Fedorik and Abdulkader M. Afifi

The Dead Sea Transform (DST) extends from the Red Sea to the East Anatolian Fault, displaying various structural styles along its ~1100 km length. In this study, we combine previous work with new mapping of fault patterns and displacements, geochronological data, and analogue and numerical modeling to provide new insights on the temporal evolution of the DST.

In the southern DST, we mapped a 30 km wide distributed shear belt along the eastern margin of the Gulf of Aqaba (GOA), consisting of a distributed shear faulting, similarly to the western belt in Sinai. Total left lateral offset across the eastern distributed shear belt is ~ 15 km, with offset across individual faults ranging from a few meters up to 5.7 kilometers. Ar-Ar dating of sheared basalt dikes and U-Pb dating of calcite cements in faults indicate that the distributed shear system was activate between 22-16 Ma, overlapping with the rifting of the proto Red Sea and Gulf of Suez. This distributed shear is observed along the GOA and the deformed area narrowed along the Arava Valley. Distributed shearing marks the initial stage of continental break-up along the DST, which was abandoned by faulting concentration within the GOA and propagation of the DST towards the north.

The structural analysis of bathymetry data from the GOA and fault mapping along the entire DST highlight various structural styles: rotational transtension within the GOA, narrowing to simple strike-slip faulting of the Wadi Araba and Jordan Valley, and pull-apart basins along the Dead Sea, Sea of Galilee and Hula Basin. These structures are linked at depth to the principal displacement zone, nowadays-active plate boundary. Our analogue model produces similar structural styles and with the seismicity data it confirms that deformed area narrowed in the more recent stage of deformation. We also present an approach based on the boundary element method at the regional scale to test the structural interpretation of a complex transpressional mountain range of Lebanon Restraining Bend. These results are validated by structural evidences and highlight that various structural styles lead to formation of Mt. Lebanon, Anti-Lebanon and Palmyrides structures.

This review study of the DST emphasizes the role of structural styles, inherited structures and relative movement between tectonic plates in the transform continental break-up evolution.

How to cite: Fedorik, J. and Afifi, A. M.: Structure and evolution of the Dead Sea Transform, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15463, https://doi.org/10.5194/egusphere-egu23-15463, 2023.

11:05–11:15
|
EGU23-16089
|
ECS
|
On-site presentation
Alpay Özdemir, Uğur Doğan, Jorge Jara, Semih Ergintav, Romain Jolivet, and Ziyadin Çakır

Aseismic slip (creep) is critical above the onset, propagation, and time of occurrence of large earthquakes on active faults. Also elastic strain in the crust between large earthquakes is controlled by the aseismic slip along the active faults. Key characteristics of aseismic slip behavior is that it is typically very slow and gradual, with the faults moving only a few millimeters or centimeters per year. This type of movement is often difficult to detect and measure, and may not be immediately apparent to observers.

Although it has been determined that the İsmetpaşa segment of the North Anatolian Fault has been slipped aseismically since 1970, without producing an earthquake, there is no reliable and detailed information about the spatial and temporal changes of this movement. After it was first recognized by Ambraseys in 1970, the creep movement is monitored by the researchers with terrestrial and campaign type GNSS measurements in the 6-point geodetic network established in Hamamlı. InSAR observations has made it possible to derive maps of ground velocities over the past 20 years that indicate aseismic slip is present along a ~100 km portion of the fault. Additionally, the aseismic slip rate changes spatially along the strike, peaking at 15–24 km to the east of Ismetpasa. Furthermore, InSAR time series and creepmeter measurements shows that aseismic slip in the Ismetpasa region behaves episodically rather than continuously, with stationary periods alternated with transient episodes of relatively rapid aseismic slip. These observations raise questions about how slip accommodates tectonic stress along the fault, which has important implications for hazard along the seismogenic zone.

To answer these questions, it is necessary to expand terrestrial observation capacity along the creeping segment and to conduct a detailed examination of the change in creep accelerations by associating it with seismological activity. We established ISMENET -Ismetpasa Continuous GNSS Network- in July 2016 to monitor spatial and temporal variations in the aseismic slip rate and to detect slow slip events along the fault. ISMENET stations are located approximately 120 kilometers along strike. Stations are located within 200m to 10 km of the fault to investigate the shallow, fine spatiotemporal behavior of aseismic slip. In addition to this network, 19 GNSS stations belonging to the TUSAGA-Aktif network located in the vicinity of the İsmetpaşa segment have been added to this network. To reduce the influence of non-tectonic noises, we analyze the GNSS time series to extract the signature of creep movement using Multivariate Singular Spectrum Analysis (M-SSA). Initial estimations shows that creep rates change along the fault between 6-8 mm/yr at a 4-5 km depth 10 km east side of the Ismetpaşa town. On the western edge of the Ismetpaşa segment between Bayramören and Ilgaz towns creep rate decreases ~3-4 mm/yr.

In this study, we examine the results of the temporal and spatial variation of the aseismic slip between 2016-2023 from the GNSS stations located in the immediate vicinity of the İsmetpaşa segment.

Ismetpasa, Aseismic slip, GNSS, M-SSA, NAFZ

How to cite: Özdemir, A., Doğan, U., Jara, J., Ergintav, S., Jolivet, R., and Çakır, Z.: Monitoring spatio-temporal evolution of aseismic slip along the Ismetpasa segment between 2016-2023 with GNSS measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16089, https://doi.org/10.5194/egusphere-egu23-16089, 2023.

11:15–11:25
|
EGU23-14343
|
On-site presentation
Cengiz Yildirim, Daniel Melnick, Okan Tüysüz, Cevza Damla Altınbaş, Julius Jara-Munoz, Konstantinos Tsanakas, Orkan Özcan, and Manfred Strecker

The Cyprus Arc is one of the major sources of earthquakes in the Eastern Mediterranean Region. There is limited large-magnitude earthquake activity during the instrumental period. Still, archeoseismological data imply the occurrence of large-magnitude earthquakes that hit the island and gave rise to casualties and destructions. Nevertheless, these data are insufficient to give information about the source of the earthquakes. In this study, we focussed on coastal geomorphology to unravel paleoseismic activity, at least generated by near offshore faults, that released sufficient seismic energy to deform the shoreline in Holocene.

We mapped coseismically uplifted abrasion platforms, tidal notches, fish tanks and a surface rupture implying active near offshore faults in Holocene. The elevation of paleo shorelines varies between 0.4 m to 3 m above sea level, indicating multiple occurrences of paleo earthquakes. Our radiocarbon 14C ages from biological markers (algal rims, etc) indicate that the coseismic uplift of the shoreline starts from 4,5 ka to 1.2 ka BP.

The ages of the paleoearthquakes display non-uniform spatial distribution and show migration of paleoearthquakes from west to east, especially along the island's northern coast. This study is supported by Istanbul Technical University Research Fund (Project No: 37548) and Alexander von Humboldt Foundation, Germany.

How to cite: Yildirim, C., Melnick, D., Tüysüz, O., Altınbaş, C. D., Jara-Munoz, J., Tsanakas, K., Özcan, O., and Strecker, M.: Paleoseismicity of Northern Cyprus, implications from coastal geomorphology and geochronology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14343, https://doi.org/10.5194/egusphere-egu23-14343, 2023.

11:25–11:45
|
EGU23-11399
|
solicited
|
Highlight
|
On-site presentation
Andy Nicol, Vasiliki Mouslopoulou, John Begg, Vasso Saltogianni, and Onno Oncken

The eastern Mediterranean island of Crete is located on the overriding plate of the Hellenic subduction thrust which is curved and changes strike from ~170° to ~50° in a west to east direction. Crete is located in the zone of maximum curvature of the subduction thrust. Basin and range topography together with prominent limestone scarps indicate that Quaternary deformation at the ground surface on Crete is dominated by normal faults with slip rates of up to ~1 mm/yr. These active faults comprise two primary sets that strike N-NNE (0-30°) and E-ESE (90-120°), with the more easterly faults dominating in southern Crete. Each fault set is characterised by dip slip and together they accommodate coeval W-WNW and N-NNE crustal extension. The E-ESE normal faults are approximately parallel to the strike of the subducting North African plate and form part of a regional fault system that swings in strike in sympathy with depth contours on the top of the concave northwards plate. By contrast, N-NNE normal faults are sub-parallel to the line of maximum curvature on the subduction thrust. These geometric relationships support the view that normal faulting on Crete formed, at least partly, in response to Cenozoic slab retreat (e.g., Jolivet et al., 2013), which continued into the Quaternary. In this model contemporaneous multi-directional crustal extension on Crete is driven by geologically simultaneous westward and southward retreat of the slab.

 Jolivet, L., Faccenna, C., Huet, B., Labrousse, L., Le Pourhiet, L., Lacombe, O., et al. (2013). Aegean tectonics: Strain localisation, slab tearing and trenchretreat. Tectonophysics, 597–598, 1–33. https://doi.org/10.1016/j.tecto.2012.06.011

How to cite: Nicol, A., Mouslopoulou, V., Begg, J., Saltogianni, V., and Oncken, O.: Geometry and kinematics of active normal faulting on Crete; implications for Hellenic subduction slab retreat, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11399, https://doi.org/10.5194/egusphere-egu23-11399, 2023.

11:45–11:55
|
EGU23-8915
|
Highlight
|
On-site presentation
Jorge Jara, Romain Jolivet, Alpay Ozdemir, Ugur Dogan, Ziyadin Çakir, and Semih Ergintav

Recent observations suggest seismogenic faults release elastic energy through a wide variety of slip modes covering a spectrum from sudden rapid earthquakes to slow aseismic slip. Aseismic slip releases energy very slowly without radiating seismic waves and plays an important role in the initiation, propagation, and arrest of large earthquakes. Aseismic slip is thought to be influenced by the presence/migration of fluids, stress interactions through fault geometrical complexities, and/or fault material heterogeneities. Descriptions of occurrences of aseismic slip at the surface and depth are hence required to feed into models and eventually characterize the factors controlling the occurrence of slow, aseismic versus rapid, seismic fault slip.

We focus on the central segment of the North Anatolian Fault, which has been creeping since at least the 1950s. This region was struck by the Mw 7.3 Bolu/Gerede earthquake in 1944, and since then, no earthquake of magnitude greater than 6 has been recorded. During the 1960s, aseismic slip was discovered as a wall built across the fault in 1957 was being slowly offset. Geodetic studies (InSAR, GNSS, and creepmeters) focused on capturing and analyzing aseismic slip around the village of Ismetpasa. Creepmeter measurements during the 1980s and 2010s, along with InSAR time series analysis, suggest that aseismic slip occurs episodically rather than persistently.

We use Sentinel-1 time series and GNSS data to provide a spatio-temporal description of the kinematics of fault slip. We show that aseismic slip observed at the surface is coincident with a shallow locking depth and that slow slip events with a return period of 2.5 years are restricted to a specific section of the fault. We contrast such results with GNSS time series analysis of a local network, confirming our findings. In addition, we discuss the potential rheological implications of our results, proposing a simple alternative model to explain the local occurrence of shallow aseismic slip at this location.

How to cite: Jara, J., Jolivet, R., Ozdemir, A., Dogan, U., Çakir, Z., and Ergintav, S.: Aseismic slip behavior along the central section of the North Anatolian Fault: insights from geodetic observations., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8915, https://doi.org/10.5194/egusphere-egu23-8915, 2023.

Posters on site: Thu, 27 Apr, 16:15–18:00 | Hall X2

X2.268
|
EGU23-5380
|
ECS
Fabien Caroir, Frank Chanier, Dimitris Sakellariou, Fabien Paquet, Julien bailleul, Louise Watremez, Virginie Gaullier, and Agnes Maillard

          The North Anatolian Fault (NAF) is one of the major active structures in the Eastern Mediterranean. Its right-lateral strike-slip fault initiated in eastern Turkey 13 Ma ago. The NAF westward propagation during Neogene and Quaternary times delineates the plate boundary between Eurasia and Anatolia-Aegean. The western termination of NAF is currently located in the North Aegean Trough (NAT) where NAF displays a NE-SW direction. In the NAT, the NAF termination is located near to the Sporades Islands. In the western prolongation of this termination, there is a wide domain characterised by distributed deformation. This major extensional area is mainly constituted by the Corinth rift and the North Evia domain, our study area. The whole zone experience a relative high seismicity with strike-slip focal mechanisms, especially right-lateral displacements along NE-SW-striking faults, which are mainly located between the North Evia domain and the Southern Thessaly.

          Our study is mostly based on new very-high-resolution seismic reflection profiles (Sparker) acquired during the WATER surveys (Western Aegean Tectonic Evolution and Reactivations) in July-August 2017 and 2021, onboard the R/V “Téthys II”. We also analysed several seismicity catalogues in order to connect the recent structures from seismic lines to active tectonics over the region. The interpretations from these datasets emphasize the evolution of the deformation of the North Evia domain, in particular, along the NE-SW striking lineament “Lichades Area – Oreoi Channel – Skiathos Basin” (L-O-S).

          The deformation in the Lichades Area is dominated by numerous active normal faults striking W-E or WNW-ESE and showing metric-scale offsets (up to 5 m.) within the Holocene sequence. One of the largest sub-active to active fault is striking NE-SW, parallel to the Oreoi Channel, and thus strongly oblique to the main rift deformation. The Oreoi Channel is a marine straight linking the Lichades Area and the Skiathos Basin. The seismic profiles highlight normal faults of different ages with a NE-SW direction. In the south-east, the Oreoi Channel is delineated by the Oreoi Fault, a mainly onshore normal fault which is dipping towards north-west. The Skiathos Basin is a newly discovered structure from our seismic dataset that is separated from the Skopelos Basin by a NE-SW striking acoustic ridge. The Skiathos Basin presents two main depocenters individualized by areas of rising acoustic basement. Some normal faults, oriented NE-SW and W-E, have been identified in the basin. Finally, many earthquakes focal mechanisms located in the Skiathos Basin and the Oreoi Channel indicate strike-slip faulting, with a right-lateral motion along the NE-SW direction.

          This detailed structural analysis together with the synthesis of seismic activity allow to propose a tectonic map with new insights on the recent deformation of the key-area “L-O-S” in the south-western prolongation of NAF. The Skiathos basin development shows indications of transtensive deformation. The Oreoi Channel is controlled by NE-SW-striking faults with a right-lateral component and the Lichades Area displays several fault with oblique direction and pure extension. We propose that the L-O-S tectonic system prolongs the NAF system and may progressively evolve as the future plate boundary.

How to cite: Caroir, F., Chanier, F., Sakellariou, D., Paquet, F., bailleul, J., Watremez, L., Gaullier, V., and Maillard, A.: Strike-slip faulting in the western prolongation of the North Anatolian Fault: the Lichades – Oreoi Channel – Skiathos Basin lineament, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5380, https://doi.org/10.5194/egusphere-egu23-5380, 2023.

X2.269
|
EGU23-5855
|
ECS
Chris Ogden and Ian Bastow

Understanding the crustal structure of the Anatolian Plate has important implications for its formation and evolution, including the extent to which its high elevation is maintained isostatically. However, the numerous teleseismic receiver function studies from which Anatolian Moho depths have been obtained return results that differ by <21km at some seismograph stations. Thus, we determine Moho depth and bulk crustal Vp/Vs ratio (K) at 582 broadband seismograph stations across Anatolia, including ~100 for which H-K results have not been reported previously. We use a modified H-K stacking method in which a final solution is selected from a suite of up to 1000 repeat H-K measurements, each calculated using randomly-selected receiver functions and H-K input parameters, with the result quality assessed by ten quality control criteria. By refining Moho depth constraints, including identifying 182 stations, analysed previously, where H-K stacking yields unreliable results (particularly in Eastern Anatolia and the rapidly-uplifting Taurides), our new crustal model (ANATOLIA-HK21) provides fresh insight into Anatolian crustal structure and topography. Changes in Moho depth within the Anatolian Plate occur on a shorter length-scale than has sometimes previously been assumed. For example, crustal thickness decreases abruptly from >40km in the northern Kirsehir block to <32km beneath the Central Anatolian Volcanic Province and Tuz Golu basin. Moho depth increases from 30-35km on the Arabian Plate to 35-40km across the East Anatolian Fault into Anatolia, in support of structural geological observations that Arabia-Anatolia crustal shortening was accommodated primarily on the Anatolian, not Arabian, Plate. However, there are no consistent changes in Moho depth across the North Anatolian Fault, whose development along the Intra-Pontide and Izmir-Ankara-Erzincan suture zones was more likely the result of contrasts in mantle lithospheric, not crustal, structure. While the crust thins from ~45km below the uplifted Eastern Anatolian Plateau to ~25km below lower-lying western Anatolia, Moho depth is generally correlated poorly with elevation. Residual topography calculations confirm the requirement for a mantle contribution to Anatolian Plateau uplift, with localised asthenospheric upwellings in response to slab break-off and/or lithospheric dripping/delamination example candidate driving mechanisms.

How to cite: Ogden, C. and Bastow, I.: The Crustal Structure of the Anatolian Plate: Evidence from Modified H-K Stacking of Teleseismic Receiver Functions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5855, https://doi.org/10.5194/egusphere-egu23-5855, 2023.

X2.270
|
EGU23-7674
Michelle Vattovaz, Nicolò Bertone, Claudia Bertoni, Lorenzo Bonini, Angelo Camerlenghi, Anna Del Ben, and Richard Walker
 

The eastern Mediterranean has been the locus of catastrophic earthquakes and related tsunamis (e.g., the 365 Crete and 1222 Cyprus earthquakes). The primary sources of these seismic events are structures related to the subduction of the Nubian Plate along the Hellenic and Cyprus arcs.  A detailed identification and description of the potential tsunamigenic sources are required as part of an assessment of earthquake and tsunami hazards. Here we focus on the Cyprus Arc region, in which the oceanic crust is still subducting beneath the Anatolian Plate in the west, whereas in the eastern sector, the oceanic crust has been completely subducted, and the lower plate consists of thinned continental crust. The rates of shortening are higher in the western sector than in the east. During recent decades, new data from extensive hydrocarbon exploration have allowed us to image structures that deform the seafloor and influence the shape of the recent basins in the eastern sector. The Latakia Ridge is the most prominent tectonic structure in the area. The present-day architecture of this ridge is the result of Meso-Cenozoic convergence followed by a transpressive phase related to the northward migration of the Arabian Plate. Therefore, the present geometry of the tectonic structure results from a complex interplay between reverse and strike-slip faults. Our reinterpretation of previously published seismic reflection profiles crossing the Latakia Ridge allows us to reconstruct the geometry of the main active faults and suggests their recent kinematics. Our findings could be crucial for the reassessment of seismic and tsunami hazards in the eastern sector of the Cyprus Arc. 

How to cite: Vattovaz, M., Bertone, N., Bertoni, C., Bonini, L., Camerlenghi, A., Del Ben, A., and Walker, R.: Geometry and kinematics of the active structures along the Latakia Ridge (Cyprus Arc), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7674, https://doi.org/10.5194/egusphere-egu23-7674, 2023.

X2.271
|
EGU23-9062
Ali Ozgun Konca, Sezim Ezgi Guvercin, and Figen Eskikoy

On November 23, 2022 an Mw6.0 earthquake struck northwest Turkey. The location of this earthquake is along the boundary of the northeast striking Karadere and east striking Düzce segments of the North Anatolian Fault. Remarkably the area had already ruptured twice during the 1999 Mw7.4 Izmit and Mw7.1 Düzce earthquakes. In this study we analyzed the seismicity, aftershocks and the co-seismic rupture of the 2022 earthquake. Relocated aftershocks reveal a north dipping rupture plane consistent with the previously known fault segments. We modeled the co-seismic slip using InSAR data from Sentinel-1 satellite and near-source seismic waveforms. The kinematic model shows an up-dip bilateral rupture with majority of the slip to the west of the hypocenter.  While the slip is primarily right-lateral there is significant normal component. The fact that the rupture occurred at the junction of two segments, its depth extent and oblique rake angle implies that the 2012 earthquake ruptured along a geometrical complexity that sustained a remanent slip deficit after the 1999 earthquakes.

How to cite: Konca, A. O., Guvercin, S. E., and Eskikoy, F.: Source Model of the 2022 Mw6.0 Gölyaka, Düzce (Western Turkey) Earthquake, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9062, https://doi.org/10.5194/egusphere-egu23-9062, 2023.

X2.272
|
EGU23-10222
Ian Bastow, Christopher Ogden, Thomas Merry, Rita Kounoudis, Rebecca Bell, Saskia Goes, and Pengzhe Zhou

The eastern Mediterranean hosts extensional, strike-slip, and collision tectonics above a set of fragmenting subducting slabs. Widespread Miocene-Recent volcanism and ~2km uplift has been attributed to mantle processes such as delamination, dripping and/or slab tearing/break-off. We investigate this region using broadband seismology: mantle tomographic imaging (Kounoudis et al., 2020), SKS splitting analysis of seismic anisotropy (Merry et al., 2021), and receiver function study of crustal structure (Ogden & Bastow, 2021). Anisotropy and crustal structure are more spatially variable than recognised previously, but variations correspond well with tomographically-imaged mantle structure. Moho depth correlates poorly with elevation, suggesting crustal thickness variations alone do not explain Anatolian topography: a mantle contribution, particularly in central and eastern Anatolia, is needed too. Lithospheric anisotropy beneath the North Anatolian Fault reveals a mantle shear zone deforming coherently with the surface, while backazimuthal variations in splitting parameters indicate fault-related lithospheric deformation. Anisotropic fast directions are either fault-parallel or intermediate between the principle extensional strain rate axis and fault strike, diagnostic of a relatively low-strained transcurrent mantle shear zone.

How to cite: Bastow, I., Ogden, C., Merry, T., Kounoudis, R., Bell, R., Goes, S., and Zhou, P.: Broadband seismological analyses in the Eastern Mediterranean: implications for late-stage subduction, plateau uplift and the development of the North Anatolian Fault, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10222, https://doi.org/10.5194/egusphere-egu23-10222, 2023.

X2.273
|
EGU23-11592
|
ECS
Manuel-L. Diercks, Ekbal Hussain, Zoë K. Mildon, and Sarah J. Boulton

Active tectonics in south-western Turkey is dominated by rapid N-S extension at a rate of 22 mm/a (e.g. Aktug et al., 2009), which is mostly accommodated by several large E-W trending, graben-forming normal fault zones. Seismic activity of these fault zones appears to vary both spatially and temporally (e.g. Leptokaropoulos et al., 2013). Generally, Synthetic Aperture Radar interferometry (InSAR) is a useful technique to assess the recent deformation of fault zones and locate potentially creeping segments. However, as Sentinel-1 satellites orbit the Earth on approximately N-S directed tracks, line-of-sight (LOS) velocities are relatively insensitive to N-S deformation and therefore it can be a challenge to resolve deformation in this direction. With its rapid N-S extension, the SW-Anatolian graben system is a suitable study area to develop an approach to derive a tectonic N-S deformation signal from Sentinel-1 InSAR.

We compute InSAR LOS velocities from Sentinel-1 data for all ascending and descending frames covering the study area. A least-squares inversion is used to decompose the LOS velocities into north, east and up components. To reduce the number of unknowns, we constrain the E-W component with interpolated GNSS velocities, so we effectively only invert for N-S and up components. Mathematically, the inversion requires at least two time series products to be solved, but given the low sensitivity of InSAR to N-S deformation, we use three Sentinel-1 scenes, with at least one from ascending and descending tracks to increase the accuracy. As a result, this approach is limited to regions where either two ascending or two descending tracks are overlapping, which fortunately covers most of the large grabens in Western Turkey. Using our new technique, we compute a smooth velocity field for all three components of motion (N-S, E-W and up-down) on a N-S swath crossing all major E-W-trending normal fault systems in the region, at a pixel resolution of about 100x100 m. With some improvements to come, we are able to calculate swath profiles displaying surface deformation across all fault zones. Our approach resolves both the broad scale velocity field and localised deformation differences across individual fault zones.

Compared to GNSS velocities, InSAR has a much higher resolution, allowing us to infer localised information on surface deformation in the vicinity of major fault zones instead of just quantifying a broad, regional trend. This can be used to assess individual fault zones, quantify changes in N-S surface deformation across faults and compare these results with recorded seismicity to reveal detailed insights into the active deformation of the largest fault zones in the region. Once the technique is established, we aim to expand the studied region. This study shows that overlapping tracks of Sentinel-1 data are a valuable resource, enabling detailed analysis of fault zones that are otherwise hard to assess by InSAR data from N-S orbiting satellite systems.

References:

Aktug et al. (2009). Journal of Geophysical Research, 114(B10), B10404. https://doi.org/10.1029/2008JB006000

Leptokaropoulos et al. (2013) Bulletin of the Seismological Society of America, 103(5), 2739–2751. https://doi.org/10.1785/0120120174

How to cite: Diercks, M.-L., Hussain, E., Mildon, Z. K., and Boulton, S. J.: High-resolution N-S deformation of active normal faults in SW Turkey derived from Sentinel-1 InSAR time series, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11592, https://doi.org/10.5194/egusphere-egu23-11592, 2023.

X2.274
|
EGU23-12408
Orecchio Barbara, Debora Presti, Silvia Scolaro, and Cristina Totaro

The seismic activity occurred in the last decades in the Adriatic Sea region has been investigated by means of new hypocenter locations, waveform inversion focal mechanisms and seismogenic stress fields. After a preliminary evaluation of seismic distribution, the Bayloc non-linear probabilistic algorithm has been used to compute hypocenter locations for the most relevant seismic sequences and to carefully evaluate location quality and seismolineaments reliability. We also provided an updated database of waveform inversion focal mechanisms integrating data available from official catalogs with original solutions we properly estimated by applying the waveform inversion method Cut And Paste. This database has been used to compute seismogenic stress fields through different inversion algorithms. The seismic activity, mainly concentrated in the Central Adriatic region, indicates high fragmentation and different patterns of deformation. In particular, our results highlighted the presence of two NW-SE oriented, adjacent volumes: (i) the northeastern one, characterized by pure compressive domain with NNE-trending axis of maximum compression, and mainly W-to-NW oriented seismic sources; (ii) the southwestern one, characterized by a transpressive domain with NW-trending axis of maximum compression, where thrust faulting preferentially occurs on ENE-to-NE oriented planes and strike-slip faulting on E-W ones. We jointly evaluated seismic findings of the present study and kinematic models proposed in the literature for the Central Adriatic region. The present analysis, furnishing new seismological results provide additional constraints useful for better understanding and modeling the seismotectonic processes occurring in the Adriatic Sea region.

How to cite: Barbara, O., Presti, D., Scolaro, S., and Totaro, C.: Evaluating the seismic activity of the Adriatic Sea region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12408, https://doi.org/10.5194/egusphere-egu23-12408, 2023.

X2.275
|
EGU23-14310
|
ECS
|
İrem Çakır, Cengiz Zabcı, Mehmet Köküm, Hatice Ünal Ercan, Havva Neslihan Kıray, Müge Yazıcı, Mehran Basmenji, Özlem Yağcı, N. Beste Şahinoğlu, Uğur Doğan, and Semih Ergintav

The multi-disciplinary studies yield a more complicated picture on seismic cycles, especially with the increasing evidence on creeping, slow slip events, tremors and repeating earthquakes. Recent observations support triggering of large earthquakes even by small or slow earthquakes and creeping of different portions of the fault. The Palu-Hazar Lake section of the East Anatolian Fault (EAF) is an example place of such kind of behaviour, where the 24 January Mw 6.8 Sivrice Earthquake was nucleated along the neighbouring segments. This sinistral strike-slip fault forms the eastern boundary of the Anatolian Scholle between Karlıova (Bingöl) in the northeast and Türkoğlu (Kahramanmaraş) in the southwest within the complex tectonic frame of the Eastern Mediterranean.

In this study, we aim to correlate any potential influence of bedrock lithology on this creeping section of the EAF. First, we revised the active fault and geological maps by using the multi spectral satellite images (e.g., Landsat 8 OLI) and high-resolution digital surface models (~0.65 m ground pixel resolution). Then, we determined potential exposures along the EAF and made systematic sampling both from cohesive and incohesive fault rock exposures within our study region. Collected samples are prepared for X-ray diffraction (XRD) measurements, especially for the determination of the fault clay types. Fault rock samples from ophiolitic (mafic and ultramafic) rocks and accretionary complexes (shale, sandstone, volcanics, ophiolite fragments) are mostly made of vermiculite and include minor amounts of smectite and chlorite according to our XRD measurements. Although the low shear strength of vermiculate may trigger aseismic slip at shallow depths with change in pore water pressure, it is possible that there may be no correlation between bedrock lithology and creeping, considering the poorly known seismic history of the EAF.

This study is supported by TÜBİTAK Project no. 118Y435.

Keywords: earthquake, East Anatolian Fault, creep, fault rocks

How to cite: Çakır, İ., Zabcı, C., Köküm, M., Ünal Ercan, H., Kıray, H. N., Yazıcı, M., Basmenji, M., Yağcı, Ö., Şahinoğlu, N. B., Doğan, U., and Ergintav, S.: Influence of fault rocks’ mineralogy on fault behaviour: implications from the Palu-Hazar Lake section of the East Anatolian Fault (Elazığ, Türkiye), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14310, https://doi.org/10.5194/egusphere-egu23-14310, 2023.

X2.276
|
EGU23-13724
|
ECS
|
Efe T. Ayruk, Seda Özarpacı, Alpay Özdemir, İlay Farımaz, Volkan Özbey, Semih Ergintav, and Uğur Doğan

North Anatolian Fault (NAF) is one of the most important transform faults over in World. NAF produced an important earthquake sequence Mw ≥ 7 in the 20th century, that migrates westward between 1939 and 1999. The earthquake sequence has broke the great part of the NAF which is approximately 1000 km. Due to this seismic activity of NAF, it is important to keep strain accumulation up to date and use the recent data. Many precious works have been studied to clarify the kinematics of NAF using the data that collected with geodetic methods (terrestrial and space geodetic).

In this study, we compiled published GNSS data and analyzed it to understand the present strain accumulation of NAF, with TDEFNODE block modelling code using a simple block geometry. The study area extends between Sapanca Lake at the west (Sakarya) to Yedisu at the east (Bingöl) and it stretches out in the north-south direction from the north coast of Blacksea to 130 kilometers south.

The 90% of GNSS velocity field have RMS values less than 2 mm and the accuracy of estimated slip rates is increased. Additionally, with the dense station distributions in the near field, spatial resolution improved, dramatically.

According to the first order results, fault slip rates are estimated as 20.5 mm/yr at the east and 21.6 mm/yr at the west. Locking depth is also estimated as 15 km at the east while the middle and the west part of the study area has shallower locking depth values.

In the presentation, we will demonstrate the power of our new GNSS velocity field and discuss its contribution to the understanding of the NAF kinematics in detail.

keywords: North Anatolian Fault, Block Modelling, Velocity Field

How to cite: Ayruk, E. T., Özarpacı, S., Özdemir, A., Farımaz, İ., Özbey, V., Ergintav, S., and Doğan, U.: Kinematics of North Anatolian Fault Under the Constrain of New GNSS Velocity Field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13724, https://doi.org/10.5194/egusphere-egu23-13724, 2023.

X2.277
|
EGU23-13568
|
ECS
|
İlay Farımaz, Uğur Doğan, Semih Ergintav, Ziyadin Çakır, Cengiz Zabcı, Seda Özarpacı, Alpay Özdemir, Efe Turan Ayruk, Figen Eskiköy, Alpay Belgen, and Rahşan Çakmak

The North Anatolian Fault (NAF) was broken over the last century by a series of Mw > 7 earthquakes, most of which migrated westward, starting from the 1939 Erzincan Earthquake and ending with the 1999 Izmit and Düzce Earthquakes.  For 23 years the area remained silent for destructive earthquakes but also produced relatively small seismic activities until November 23, 2022 Düzce Earthquake, Mw 5.9.

In this study, we aim to investigate the source mechanism for the 23rd November 2022 Düzce Earthquake and associate it to the ruptures of 1999 Izmit and Düzce Earthquakes. For this purpose, in the same day that the earthquake occurred, our team established 8 new continuous GNSS sites covering the area to monitor the postseismic deformation and surveyed the historical sites to estimate coseismic field. Additionally, a stack of interferograms has been interpreted from Sentinel-1 data to densify the deformation fields.

Based on our first order analysis, the earthquake occurred at the overlap of the rupture zones of 1999 Izmit and Düzce Earthquakes (west of Eftani Lake on Düzce segment). Our GNSS and InSAR monitoring showed that the coseismic deformation is around <6 cm in the near field and ~33% of the InSAR coseismic deformation field is related with postseismic deformations.  

 

Keywords: Düzce earthquake, Coseismic and early postseismic deformation, InSAR, GNSS

How to cite: Farımaz, İ., Doğan, U., Ergintav, S., Çakır, Z., Zabcı, C., Özarpacı, S., Özdemir, A., Ayruk, E. T., Eskiköy, F., Belgen, A., and Çakmak, R.: Coseismic and Early Postseismic of 23 November 2022 Mw = 5.9 Düzce Earthquake with InSAR and GNSS Measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13568, https://doi.org/10.5194/egusphere-egu23-13568, 2023.

X2.278
|
EGU23-9851
|
ECS
Sezim Ezgi Güvercin, Mironov Alexey Pavlovich, Seda Özarpacı, Hayrullah Karabulut, Vadim Milyukov, Semih Ergintav, Cengiz Zabcı, Ali Özgün Konca, Uğur Dogan, Ruslan Dyagilev, Steblov Grigory Mikhailovich, and Eda Yıldıran

The active deformation and shortening in the Caucasus region are predominantly driven by the collision of Arabian and Eurasian plates where significant differences in the surface uplift, large basins, variations on the plate motion rates along the convergence are observed. To the west of the region the lack of sub-crustal seismic activity, low velocity anomalies in tomographic images and the decreased rate of shortening imply that western Caucasus has different kinematics compared to its east. Previous studies suggested that either slab detachment or lithospheric delamination is responsible for the complex deformation beneath the Caucasus. Large uncertainties due to sparse and non-uniform data coverage for local and regional tomography studies, diffuse seismicity, significant crustal thickness variations and strain field lead to poor understanding on the formation and active deformation of this fold and thrust belt. In this study, we aim to obtain a joint database collected from Turkey and Russia between 2007 and 2020. A waveform data base is created from 37 stations in Russia and more than 60 stations in Turkey. An improved seismicity catalog is built including relocated earthquakes with more than 100 stations. The crustal thickness map of the study region is updated by receiver function analysis using stations both from Turkey and Russia covering the Greater Caucasus. A high resolution Pn tomographic model is computed to determine velocity perturbations in uppermost mantle. The data from GNSS (Global Navigation Satellite System) stations both in Turkey and Russia are processed together for the first time and used to map the updated strain field. The new strain field is correlated with the crustal stress orientations from earthquake source mechanisms. New block models are determined for the Caucasus region in order to better estimate the block boundaries and related slip rates. By the improved azimuthal coverage of the seismic and geodetic stations the uncertainties of vertical and horizontal earthquake locations and the velocity field are reduced, thus; a reliable source for the geometry and kinematics of the faults in the Caucasus region is obtained. With the improved seismological and geodetic observations, reliable inferences on the seismic hazard and earthquake potential is expected for the region.

 

 

How to cite: Güvercin, S. E., Pavlovich, M. A., Özarpacı, S., Karabulut, H., Milyukov, V., Ergintav, S., Zabcı, C., Konca, A. Ö., Dogan, U., Dyagilev, R., Mikhailovich, S. G., and Yıldıran, E.: Preliminary Results from Comprehensive Seismic and Geodetic Observations Around the Caucasus Region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9851, https://doi.org/10.5194/egusphere-egu23-9851, 2023.

X2.279
|
EGU23-12937
|
Highlight
Cengiz Zabcı, Erhan Altunel, and H. Serdar Akyüz

In the complex puzzling of the lithospheric plates, the transform boundaries and related strike-slip faults are under focus of earth scientists for more than a hundred years not only for their important role in the lithospheric-scale deformation, but also for being sources of destructive earthquakes. Particularly, spatial and temporal seismic behaviour of these faults has been a subject of great curiosity for several decades with a special emphasis on the relationship between their geometry and earthquake recurrence. The North Anatolian Shear Zone (NASZ) is one of these tectonic structures, which makes the northern boundary of the Anatolian Scholle connecting the Hellenic Subduction in the west and the Arabia-Eurasia Collision in the east. This dextral system has a remarkable seismic history, especially in the 20th century, when the westward migrating earthquake sequence generated surface ruptures of about 1100 km with addition of ~140 km from two out of sequence events, 1912 Mürefte and 1949 Elmalı earthquakes, leaving unbroken only Marmara in the west and Yedisu in the east along its most prominent structure, the North Anatolian Fault (NAF).

In this study, we aim to review palaeoseismic studies of more than three decades that provide invaluable information on the earthquake history all along the NAF with an attempt to understand which fault pieces have been involved in any of these palaeoevents. Thus, we decided to use their geometric properties, with an assumption that certain geometric discontinuities play an important role as end-points of an earthquake rupture. Palaeoseismological studies are grouped together according to the NAF’s geometric segments, on which they are located. In this classification, we excluded the ones with incomplete dating records or providing indirect evidence (i.e., cores). Then, we used a Bayesian approach to calculate the probability distributions of each palaeoevent, but applied it not to the individual sites but to the tectonostratigraphic data of merged trenches along the same fault segments. Our analyses suggest an ‘irregular’ seismic behaviour of the NAF although there are still gaps in data especially for the central parts. Large geometric complexities (e.g., Niksar step-over, Çınarcık Basin) significantly control the heterogenous stress conditions, but the ‘irregular’ behaviour is not only restricted to the segments close to these structures, but observed almost along the entire fault. In spite of the compiled 118 trench sites with more than 275 trenches, there is still necessity of further studies in order to increase the spatial and temporal resolution of palaeoseismic data along the NAF, especially for its central segments.

How to cite: Zabcı, C., Altunel, E., and Akyüz, H. S.: The North Anatolian Fault: an example to regularity of ‘irregular’ seismic behaviour of continental strike-slip faults, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12937, https://doi.org/10.5194/egusphere-egu23-12937, 2023.

X2.280
|
EGU23-13785
Sabrina Metzger, Md Aftab Uddin, Vasiliki Mouslopoulou, John Begg, Andy Nicol, Vasso Saltogianni, and Onno Oncken

Located on the overriding plate of the Hellenic subduction margin, the 250 km-long island of Crete offers a unique opportunity to study curved-forearc deformation. The African-Eurasian plate-convergence of ~40 mm/yr (~80 %) is primarily accommodated aseismically, but intense seismicity is recorded at the plate-interface and a reverse splay faults along the Hellenic trough; frequent M6+ earthquakes and (at least one) tsunami-genic event, causing up to 10 m of paleoshoreline uplift in western Crete, are reported. Global Navigation Satellite System (GNSS) data revealed N-S shortening of ~2 mm/yr within western Crete due to pure plate convergence. Further east, the curved subduction trench accommodates increased oblique slip, causing E-W extension of ~2 mm/yr in eastern Crete.

Recently, the European Ground Motion Service published dense InSAR surface deformation data in East and Up direction of whole Europe. The InSAR time-series comprise positioning samples every six days, respectively, every ~50 m, and, in Crete, exhibit long-wavelength deformation signals caused by deep-rooted, tectonic sources that are overlaid by (often seasonally-modulated) signals originating in shallow aquifers. We analyze these time-series in space and time and validate the results using available GNSS rates, a seismic catalog and an active fault data base. Preliminary results suggest a slight eastward tilt of Crete, which is not confirmed by published GNSS rates, and has to be investigated further. Spatially-confined uplift of up to ~5 mm/yr are observed at the karstic Omalos plateau, and up to ~30 mm/yr subsidence in the Messara basin, both probably related to groundwater replenishment/abstraction. Relative eastward motion increases towards eastern Crete, particularly in the fault zones embracing Mirabello bay and east of it, thus confirming the aforementioned E-W extension, and towards the southern coast.

How to cite: Metzger, S., Uddin, M. A., Mouslopoulou, V., Begg, J., Nicol, A., Saltogianni, V., and Oncken, O.: Recent kinematics of Crete, observed by InSAR, reveal complex, curved-forearc deformation and aquifers changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13785, https://doi.org/10.5194/egusphere-egu23-13785, 2023.

X2.281
|
EGU23-3431
|
ECS
Batuhan Kilic, Seda Özarpacı, and Yalçın Yılmaz

The primary active strike-slip faults in Turkey are the North and East Anatolian Faults (NAF and EAF), as well as the Ölüdeniz Fault. These transform boundaries are the result of various tectonic regimes, including the collapse of the oceanic lithosphere in the Hellenic and Cyprus arcs, continental collisions in the Zagros/Caucasus and Black Sea; Anatolia's related continental escape and expansion in western Turkey; and the Nubian, Arabian, and Eurasian plate interactions, which are Turkey's main tectonic domains. Block modeling may be useful for establishing slip rates for major faults or calculating block movements in order to better understand these regimes and deformations. Previous to block modeling, clustering analysis may be used to identify Global Positioning System (GPS) velocities in the absence of prior data.

Clustering analysis, as an unsupervised learning, is an essential technique to discover the natural groupings of a set of multivariate data. Its aim is to explore the underlying structure of a data set based on certain criteria, specific characteristics in the data, and different ways of comparing data. There have been many studies conducted in the last ten years that determine and investigate cluster/block boundaries without any a priori information by considering the similarity of GPS-derived velocities. With the rapid progress of clustering technology, various partitioning, hierarchical, and distribution-based techniques such as k-means, k-medoids, Balanced Iterative Reducing and Clustering using Hierarchies (BIRCH), Gaussian Mixture Model (GMM), and Hierarchical Agglomerative Clustering (HAC) have been utilized to find appropriate solutions that are acceptable and to determine boundaries before block modeling in geodetic studies.

Although clustering techniques are diverse and span in clustering GPS velocities, there are several common problems associated with clustering, including the inability of a single clustering algorithm to accurately determine the underlying structure of all data sets and the lack of consensus on a universal standard for selecting any clustering algorithm for a specific problem. To overcome this problem, ensemble clustering (consensus clustering) techniques that can employ from gathering the strengths of many individual clustering algorithms has been introduced (Kılıç and Özarpacı, 2022). Therefore, the objective of this study is to explore the performance of ensemble clustering techniques for clustering GPS-derived horizontal velocities. In the direction of this research, we used newly published horizontal velocities inferred from a combination of a dense network of long term GNSS observations in Turkey (Kurt et al., 2022). After that, we tested the number of clusters that best represents the data set using the GAP statistic algorithm, and we clustered GPS velocities using five different clustering techniques, including BIRCH, k-means, mini batch k-means, HAC, and spectral clustering. Then, we investigated the performance of three ensemble clustering techniques such as Cluster-based Similarity Partitioning Algorithm (CSPA), Hybrid Bipartite Graph Formulation (HBGF), and Meta-CLustering Algorithm (MCLA) by combining the strengths of five individual clustering algorithms. The outcome of this study revealed that the MCLA ensemble clustering algorithm can be utilized to determine cluster/block boundaries for this region and give enhanced results compared to single clustering techniques.

Keywords: Clustering analysis, GPS velocities, Ensemble clustering

 

How to cite: Kilic, B., Özarpacı, S., and Yılmaz, Y.: Investigation the performance of ensemble clustering techniques in latest GPS velocity field of Turkey, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3431, https://doi.org/10.5194/egusphere-egu23-3431, 2023.

Posters virtual: Thu, 27 Apr, 16:15–18:00 | vHall TS/EMRP

vTE.2
|
EGU23-6612
|
ECS
Meysam Amiri, Andrea Walpersdorf, Erwan Pathier, and Zahra Mousavi

The 2013 April 16 Mw 7.7 Saravan earthquake, an intra-slab earthquake with a normal faulting mechanism, occurred in the Makran subduction zone, where the Arabian oceanic lithosphere subducts northward under Iran and Pakistan. To examine the postseismic displacement of the Saravan earthquake, we processed one ascending (A13) and one descending track (D122) from 2014 to 2022. We construct 1000 and 504 interferograms for ascending and descending tracks, respectively. We remove the topographic and flatten-earth phase contributions using the 30 m Shuttle Radar Topography Mission Digital Elevation Model and precise orbital parameters. We correct the turbulent component of the tropospheric delay using atmospheric parameters of the global atmospheric model ERA-Interim provided by the European Center for Medium‐range Weather Forecast. Then, we filter the generated interferograms using Goldstein’s filter and unwrapped them with a branch-cut algorithm. Once all interferograms are corrected and unwrapped, we employ an SBAS time-series analysis based on the phase evolution through time for each pixel, to retrieve the mean velocity map and displacement through time. The mean velocity map in the LOS direction indicates a sharp signal close to the Saravan earthquake suggesting that the observed signal belongs to the postseismic phase of this event. The postseismic spatial profile derived from high-quality time series analysis of Sentinel 1-A images has the opposite pattern of displacement with respect to the coseismic profile derived from Radarsat-2 interferograms. Due to the 50-80 km depth of the earthquake, observing such a deformation approximately seven years after the earthquake is interesting and consequently, we decided to study it in detail.

Large earthquakes are usually followed by transient surface deformation which reflects the rheology of the lithosphere and sub-lithospheric mantle following three mechanisms: afterslip, viscoelastic relaxation, and poroelastic rebound. In this study, we investigate the responsible mechanism of Saravan 2013 postseismic deformation through the before mentioned mechanisms. Due to the opposite sense of deformation during co and postseismic periods, we first try to assess the viscoelastic relaxation mechanism using the PSGRN/PSCMP code. We calculate the time-dependent green functions of a given layered viscoelastic-gravitational half-space for our dislocation sources at different depths using the PSGRN code. Then, we use the result as a database for PSCMP, which discretizes the earthquake's extended rupture area into several discrete point dislocations and calculates the co- and post-seismic deformation by linear superposition. For the viscoelastic mechanism modeling, it is important to consider a proper layering and velocity structure of the earth. We use the velocity structure of the GOSH seismic station implemented by the Institute for Advanced Studies in Basic Sciences to define Green’s functions. Finally, we use the distributed fault slip resulting from coseismic linear modeling as a source for viscoelastic relaxation and modeled the surface displacement for different periods after the earthquake. In the next step, we will compare the observed postseismic deformation using InSAR analysis and modeled displacement to examine whether the viscoelastic rules the postseismic movement. ‌Besides, exploring other mechanisms like afterslip and poroelastic rebound is required to fully assess the possible mechanisms.

How to cite: Amiri, M., Walpersdorf, A., Pathier, E., and Mousavi, Z.: Seven years of postseismic deformation following Mw 7.7 2013 Saravan intra-slab earthquake from InSAR time series, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6612, https://doi.org/10.5194/egusphere-egu23-6612, 2023.

vTE.3
|
EGU23-9911
|
ECS
Aram Fathian, Cristiano Tolomei, Dan H. Shugar, Stefano Salvi, and Klaus Reicherter

On 6 January 2017, an Mw 4.9 earthquake occurred c. 40 km northeast of the city of Khonj, in the Simply Folded Belt (SFB) of the Zagros, southwestern Iran. Using the JAXA ALOS-2 PALSAR as well as the Copernicus Sentinel-1 SAR images, we applied two-pass Interferometric Synthetic Aperture Radar (InSAR) to acquire the corresponding surface deformation of the Khonj earthquake. The fault plane solutions confirm the thrust mechanism for the earthquake that has a shallow depth of 5 km resulting in a subtle, permanent surface deformation visible through InSAR displacement maps. Concentric fringes on the interferograms in both ascending and descending geometries indicate the rupture has not reached the surface; nonetheless, they indicate shallow seismic deformation within the Zagros SFB. The Khonj earthquake is one of the smallest events with a discernible InSAR deformation field of c. 5–10 cm in the satellite line-of-sight (LOS). The epicenter of the earthquake is located in a plain between the northwestern and southeastern hinges of the Qul Qul and Nahreh anticlines. The source modeling from the InSAR data quantifies an NW-SE-striking fault either dipping to the northeast or the southwest. This shallow event is aligned with a zone in which the only documented surface ruptures in the Zagros—i.e., the Furg and Qir-Karzin earthquakes—are located.

How to cite: Fathian, A., Tolomei, C., H. Shugar, D., Salvi, S., and Reicherter, K.: Shallow deformation of the Mw 4.9 Khonj earthquake (6 January 2017) in the Zagros Simply Folded Belt, Iran, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9911, https://doi.org/10.5194/egusphere-egu23-9911, 2023.

vTE.4
|
EGU23-6274
|
Zahra Mousavi, Mahin Jafari, Mahtab Aflaki, Andrea Walpersdorf, and Khalil Motaghi

The moderate magnitude (Mw 5.8) Ganaveh earthquake, as a compressive event. occurred on 2021 April 18 in the southwest of the Dezful embayment of the Zagros Mountain belt, Iran. We process Sentinel-1 SAR images in ascending and descending geometries to investigate the coseismic deformation and its source parameters. The resultant displacement maps indicate a maximum of 17 cm of surface displacement in the satellite line of sight direction with no evidence of surface rupture. The NW-oriented elliptical fringes in coseismic ascending and descending displacement maps are in agreement with the strike of the major Zagros structures. The InSAR displacement map is inverted to evaluate the earthquake source parameters and the inversion results reveal a low-angle NE-dipping fault plane characterized by a maximum dip slip of 95 cm at ~6 km depth and a slight sinistral slip component (2.9 cm). Inversion of 39 earthquake focal mechanism (from 1968 to 2021), including the Ganaveh mainshock and its five larger aftershocks indicate a regional compressional stress regime and applying this stress on the retrieved Ganaveh fault plane leads to a minor sinistral movement confirming the geodetic results. InSAR coseismic displacement and relocated mainshock and aftershocks situate on the hanging wall of the Zagros Foredeep fault. This underlines the ZFF as the causative fault of the Ganaveh earthquake. The occurrence of Ganaveh moderate magnitude earthquake on the Zagros Foredeep fault highlights its role as the western structural boundary for recurrent Mb>5 events in the Dezful embayment.

To examine the possibility of postseismic deformation after such a moderate magnitude earthquake in Zagros, we processed and created the interferograms using the Sentinel-1 SAR images based on the SBAS timeseries analysis approach after the mainshock until the end of 2021. The time series analysis of the constructed interferograms indicates a maximum of 7 cm of postseismic deformation with a similar strike and shape as the coseismic displacement. The short-term postseismic displacement of the Ganaveh earthquake is released seismically by aftershocks. The agreement between the cumulative displacement, cumulative number of aftershocks, and their related moment release through time and the similar pattern and direction of postseismic and coseismic deformation suggest that an afterslip mechanism can be the causative mechanism of the Ganaveh postseismic motion. We estimate a maximum of 30 cm slip at a depth of ~5 km along the coseismic causative fault plane by inverting the postseismic cumulative deformation map.

How to cite: Mousavi, Z., Jafari, M., Aflaki, M., Walpersdorf, A., and Motaghi, K.: InSAR constraints on coseismic and postseismic deformation of the 2021 Ganaveh earthquake along the Zagros Foredeep fault, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6274, https://doi.org/10.5194/egusphere-egu23-6274, 2023.