Elastic dislocation models have been successfully used to model co-seismic displacements in numerous studies. Expected far-field displacements (>500 km) are low and most of the time beyond uncertainty level of the global navigation satellite system (GNSS) measurements. In the case of the moment magnitude 7.8 and 7.6 Kahramanmaraş earthquakes on 6 February 2023, the Türkiye’s extensive and continuous GNSS network allowed us to show that large earthquakes can induce far-field crustal deformations (>700 kilometers), exceeding current predictions from elastic dislocation models. This and the asymmetry of the co-seismic displacements with respect to the East Anatolian fault provides crucial insights about the deformation of Earth’s crust at various scales and the interactions among tectonic plates. It also carries profound implications for seismic hazard assessments and necessitates a new perspective on crustal deformation and earthquake mechanics.
How to cite: Vernant, P., Ergintav, S., Tan, O., Karabulut, H., Özarpacı, S., Floyd, M., Konca, A. Ö., Çakır, Z., Acarel, D., Çakmak, R., Vasyura-Bathke, H., Dogan, U., Kurt, A. I., Özdemir, A., Ayruk, E. T., Turgut, M., Özel, Ö., and Farımaz, I.: GNSS measurements reveal unexpected far-field deformation of the 2023 Kahramanmaraş earthquakes, Türkiye , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6153, https://doi.org/10.5194/egusphere-egu25-6153, 2025.
Understanding and deciphering wiggles from seismograms has been a long endeavor to understand the internal structure of the Earth and to explore earthquake source properties. Here we make the first attempt to decipher the continuous rupture phases as large near-fault velocity pulses along the East Anatolian Fault in the 2023 Mw 7.8 Kahramanmaraş, Türkiye earthquake. With constraint from the near-fault data, we can resolve earthquake rupture details with unprecendented resolution. Through data analysis and dynamic rupture simulations, we robustly identify the transient supershear rupture on a segment with flat fault trace and rupture deceleration at fault bends. Our study highlights the complexity and superior application of near-fault data for understanding earthquake dynamics.
How to cite: Yang, H. and Yao, S.: Rupture phases reveal geometry-related rupture propagation in a natural earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13939, https://doi.org/10.5194/egusphere-egu25-13939, 2025.
The Kahramanmaraş earthquakes of February 6, 2023 occurred in the tectonically active eastern Mediterranean region near the Kahramanmaraş triple junction, where the Anatolian, Arabian, and African plates converge. This structurally complex boundary is characterized by significant strain accumulation, which frequently generates large-magnitude earthquakes. The significant ground shaking experienced in southeastern Turkey and surrounding areas implies the importance of high-resolution studies aimed at monitoring detailed seismotectonic processes in this region.
Here, we present a kinematic rupture model of these destructive events derived from a joint inversion of high-rate Global Navigation Satellite System (GNSS) and strong ground motion (SGM) data. We combine GNSS-derived displacement time series from continuously operating stations with displacement waveforms extracted from SGM records. We assess the correlation between these two datasets by comparing stations in close proximity, thereby evaluating the consistency and precision of the derived ground motions. In addition, the earthquake hypocenter and the surface fault trace are taken into account by classifying and grouping the data based on source-to-station geometry. We employ different filtering approaches for near-field and far-field observations to extract the displacements appropriately. We also use the Precise Point Positioning (PPP) technique to obtain the coseismic displacement of GNSS observations. Instead of traditional differential techniques, we tested kinematic PPP while still preserving the effect of ambiguity resolution. Kinematic PPP solutions are derived from raw GNSS phase and pseudorange observations, yielding precise station positions at each epoch during each earthquake separately.
To address the spatiotemporal evolution of fault slip, we apply finite fault modeling to the combined dataset and obtain a detailed kinematic rupture model for the earthquake sequence. We compare this model with previously published rupture models for the February 6, 2023 Kahramanmaraş earthquakes, highlighting both similarities in overall fault geometry and slip patterns, and differences in rupture extent and timing. By integrating high-frequency strong ground motion observations with GNSS displacements, we emphasize the importance of combining multiple data sources to gain a more comprehensive understanding of earthquake source processes.
How to cite: Özbey, V., Mutlu, B., Gumus, M. A., and Bozkurt, A. B.: Kinematic Rupture Modeling of the 6 February 2023 Kahramanmaraş Earthquakes: A Joint Inversion of High Rate GNSS and Strong Ground Motion Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15827, https://doi.org/10.5194/egusphere-egu25-15827, 2025.
The southwestern continuation of the East Anatolian Fault Zone (EAFZ), specifically its relationship with Iskenderun Basin, the Dead Sea Fault Zone (DSFZ) and Cyprus Slap is still enigmatic. In 2023, nearby splays of EAFZ in the southwest are ruptured by two large earthquakes that are nine hours apart. At first, Pazarcık earthquake (M7.8) initiated at a secondary fault, later jump to the main strand of EAFZ and propagated bilaterally producing a surface rupture exceeding 315 km in length. The Ekinözü earthquake (M7.7) triggered nine hours later also displayed bilateral rupture propagation and produced a 140 km long surface rupture. Surface deformations associated to both events that ruptured multiple fault segments with left-lateral strike-slip mechanism, are mapped in detail using satellite images and field observations. Surface offsets of both events are highly variable, reaches up to 8 m, and controlled mainly by subsurface slip. The accuracy of mapped active faults prior to the doublet, reduce significantly along plains where distributed deformations are common and occasionally surface rupture follows mapped inactive faults suggesting reactivation of old faults or unrecognized active faulting in the area.
Large 19th century earthquakes previously associated to the faults ruptured during this doublet, are likely mislocated and these segments were accumulating stress at least for 500 years. Earthquake mechanisms recorded before and after the doublet revealed strike-slip regime corresponding well with EAFZ but towards south, extensional events become abundant. Based on the computed stress field, east-west striking Çardak fault ruptured during the second event, is not optimally oriented for left-lateral failure but suffered from noticeable static stress increase and rate-and-state friction based simulations including both static and dynamic effects suggested that it was at the end of its seismic cycle. Static stress changes resulted from the doublet also indicate pronounced increases, especially along Malatya, Savrun, Türkoğlu and Antakya fault segments which are remained as seismic gaps.
GPS based slip models along multiple profiles constrained left-lateral slip rates of ruptured faults and suggested an increase in slip rate from south to north across EAFZ. During Pazarcık earthquake, rupture made a sharp bend towards south rather than following parallel fault segments towards Adana which are previously proposed as the western continuation of EAFZ. Our field observations indicated a fault traversing the Amanos mountains parallel to EAFZ along which fault kinematics and compiled GPS data together suggest left-lateral motions. Based on these findings, alternative regional kinematic models assuming Iskenderun and Maras blocks as independent or intact are established and later utilized for probabilistic seismic hazard analysis throughout the Adana basin by considering variable site conditions and basin effect in long spectral periods.
How to cite: Özacar, A. A., Ayhan, M. E., Uzel, B., Sopacı, E., Shah, S. T., Gülerce, Z., Kaymakcı, N., Okay, H. B., and Rojay, F. B.: Complex active deformation along southwestern part of the East Anatolian Fault Zone: Insights from 2023 Türkiye earthquake doublet , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9330, https://doi.org/10.5194/egusphere-egu25-9330, 2025.
The February 6, 2023 earthquake sequence in eastern Türkiye stands as one of the most catastrophic seismic events of the past century. This study presents high-resolution (centimeter-scale) drone maps of surface ruptures recorded 10 days after the event. Our dataset includes the complete rupture of the Narli segment along the Dead Sea Transform Fault, responsible for the initial Mw 7.8 earthquake, and detailed mapping of three additional rupture sites along the East Anatolia Fault Zone.
These geo-referenced maps and ground offset data reveal that the earthquake sequence commenced along the Dead Sea Transform Fault, induced by the northward displacement of the Arabian Plate. This movement subsequently triggered the slip along the East Anatolia Fault, which had accumulated significant tectonic stress. The rupture transferred both sides of the fault, resulting in extensive structural damage. The subsequent Mw 7.5 earthquake along the Çardak-Sürgü Fault, occurring nine hours later, was triggered in the same way, after a Mw 4.5 event at the intersection of the East Anatolian and Çardak-Sürgü Faults.
En echelon fracture patterns are the most common surface deformation style along all the fault zones regardless of the base rock and topography, cut basins and ridges directly instead of always following the pre-existing weak surfaces. The biggest surface offset is at the intersection of the Dead Sea Transform Fault and the East Anatolia Fault, 47.5 kilometers from the epicenter, suggesting that the surface rupture is the result of long-term accumulated stress release along the fault system, triggered by one earthquake event caused by plate motion.
Our findings offer vital insights into surface deformation features of continental strike-slip earthquakes, elucidate rupture propagation mechanisms, and shed light on the interaction and slip transfer between complex fault systems within a contemporary continental collision zone. These observations contribute to a deeper understanding of how those displacements accommodate plate motions and ”displace“ human beings at the same time.
How to cite: Meng, J., Kusky, T., Bozkurt, E., Bodur, M., and Wang, L.: High-Resolution (Centimeter-Scale) Drone Mapping of Surface Ruptures from the February 6, 2023 Earthquake Sequence in Eastern Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15202, https://doi.org/10.5194/egusphere-egu25-15202, 2025.
This study examines the first event of the doublet earthquakes (Mw 7.7 and Mw 7.6) that
impacted Türkiye on February 6, 2023. Following the earthquake, data related to surface
rupture and slip distribution were obtained using satellite-based geodetic and remote
sensing methods. While these studies are important for understanding bulk deformation;
detailed field investigations that map and measure coseismic deformation, illustrate fault
geometry, sections and jog relationships and calculate displacements from deformed
objects remain insufficient. To fill this gap, high-resolution ( <10 cm) UAV imagery was
utilized by Istanbul Technical University Earth Bee Lab to produce a continuous 300-meters-
wide strip map along the full extent of the surface rupture.
Our fault map was created based on these imagery datasets and identified a rupture length
of approximately 80 km, extending between Çiğli and Hassa. The rupture is divided into five
primary sections: İslahiye, Beyoğlu, Türkoğlu, Küpelikız and Kapıçam. Deformation zone
widths vary significantly, ranging from a few meters to 700m, with narrow, concentrated
zones in Kapıçam, Türkoğlu and Beyoğlu Sections compared to İslahiye and Küpelikız
Sections. The widest deformation zones were observed at the jogs along section
boundaries.
Displacements were categorized as ‘’On Fault’’ for those occurring along the main fault line
and ‘’Off Fault’’ more than 10 meters away from the main rupture. The aim was to reveal the slip
partitioning along the fault. Analysis of 1419 coseismic displacement measurements ( 1233
On Fault and 186 Off Fault) reveals maximum slips of 8.56 ± 0.8 m in the Beyoğlu Section
and 7.9 ± 0.3 m in Kapıçam Section with an average slip of 2.19 m. These values are higher
than the previously provided maximum displacement value of 7.3±0.2 m measured in the
Büyüknacar Area.The highest concentration and magnitude of displacements were observed
in the Beyoğlu Section and at the Beyoğlu-Küpelikız transition along the surface rupture
between Çiğli and Hassa.
How to cite: Baka, Ç. M., Yıldırım, C., Özcan, O., Karakaş Gedik, M., and Gedik, Y.: High-Resolution Coseismic Surface Displacement Measurements Between Çiğli and Hassa along the surface rupture of 6 February 2023, Kahramanmaraş Earthquake (Mw 7.8),Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6394, https://doi.org/10.5194/egusphere-egu25-6394, 2025.
The East African Rift System (EARS) is a highly seismically active continental rift characterized by frequent faulting, volcanism, and significant earthquakes that pose substantial risks to infrastructure and populations in the region. Despite numerous seismic hazard assessments, challenges such as limited earthquake data and sparse monitoring networks compromise the reliability of existing studies. Additionally, the absence of seismic design codes in many EARS countries exacerbates the vulnerability of infrastructure to earthquake damage. This review synthesizes seismic hazard research conducted over the past 50 years, with a focus on advancements in probabilistic and deterministic ground motion predictions, as well as micro- and macrozonation techniques aimed at mitigating seismic risks. The findings highlight inconsistencies in hazard estimates, primarily stemming from parameter uncertainties, emphasizing the urgent need for region-specific ground motion models tailored to the unique geological conditions of EARS and the broader African continent. A gap identified is the lack of accurate and harmonized datasets required for effective earthquake modeling. This includes the need for a comprehensive regional earthquake catalog harmonized across borders and homogenized in terms of moment magnitude (Mw). Equally important is the development of a regional database of active faults with associated slip rate information, which is essential for constructing robust earthquake source models. The goal of this review is to enhance the understanding of seismic hazards in EARS and to provide policymakers with actionable insights to support risk mitigation strategies. This is particularly necessary given the rapid population growth and infrastructure development in this region.
How to cite: Al-Ajamee, M. and Kumar, R.: Seismicity and Seismic Hazards along the East African Rift System (EARS): A Review, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3357, https://doi.org/10.5194/egusphere-egu25-3357, 2025.
The region spanning across the Ionian Sea margins in the Mediterranean is geologically complex and comparatively little evaluated, due to limited available seismic data. The poorly understood tectonic structure is however related to seismic hazard that has struck surrounding countries with devastating results in historical time.
The region contains large fault systems that extend on and offshore and are associated with dramatic lateral changes in deformation rates. However, the kinematics and activity of the main faults are poorly defined and the system are inadequately mapped.
Current knowledge we can not differentiate whether fault systems are part of a mega-thrust subduction plate boundary, or they are located above on an overriding plate, or are part of a different tectonic system, let alone we can precisely define the location, geometry and extent of plate boundary faults.
We have collected new seismic data (1.5 to 5 km long streamer) and reprocessed existing seismic data (4.5 km long streamer data) along the Ionian Sea realm during the last 10 years to study and map those system. Recently, we have been provided with industry-quality (10.5 km long streamer) lines to study remaining regions of the margins and deep basins of the region.
Our new data set provides an extensive coverage, and our new seismic images document abundant deformation that can not be easily explained by existing models of subduction-zone type of deformation, and we propose a model in which the current tectonic activity is the result of the embryonic collision process between Africa and Europe, and where the current dominant geodynamic driving forces are not longer related to slabs subducting under the continent that were previously controlling the evolution of the Mediterranean Realm.
How to cite: Ranero, C. R., Nomikou, P., Loreto, F., Merino, I., Ganas, A., Poulos, S., and Kothri, S.: Active tectonics in the Ionian Sea realm: Subduction or collision?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20695, https://doi.org/10.5194/egusphere-egu25-20695, 2025.
Geological and geophysical studies suggest that plateau uplift in regions such as Tibet, Colorado, the Andes, and Anatolia may be in part related to ‘lithospheric dripping’; a process whereby dense lithosphere is removed as a viscous instability. Recent satellite-based measurements and crustal isostasy studies, reveal an interesting tectonic puzzle at the Central Anatolian Plateau in Turkiye since the data indicate rapid subsidence of the Konya Basin within the overall uplifted plateau. Here, we combine results from 3D analogue/laboratory experiments and 2D numerical models with quantitative analyses to study lithospheric drip processes which may be responsible for this local basin subsidence within the plateau. 3D analogue models were built in the laboratory using materials such as polydimethylsiloxane (PDMS), clay, and sand to model lithospheric drip instabilities. Image correlation techniques such as Particle Image Velocimetry (PIV) and digital photogrammetry were used to monitor material flow and changes in topography of the analogue model. In conjunction, similar 2D numerical models were developed using viscoplastic rheologies with the ASPECT geodynamics code. In reconciling the models with the observations, we interpret that the Konya Basin is subsiding due to a secondary localized lithospheric dripping event following a larger scale primary dripping event that was responsible for the broad uplift of the Central Anatolian Plateau. Furthermore, the numerical and analogue experiments suggest that the local secondary drip is `asymptomatic’, in that it drives subsidence but no appreciable tectonic deformation (shortening or extension) of the crust. The findings indicate that multistage lithospheric foundering may be characteristic of the episodic development of orogenic systems.
How to cite: Andersen, J., Pysklywec, R., Göğüş, O., Uluocak, E. Ş., and Santimano, T.: Multistage lithospheric drips control active basin formation in the Central Anatolian Plateau: insights from analogue and numerical modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13197, https://doi.org/10.5194/egusphere-egu25-13197, 2025.
We present GPS observations of crustal deformation monitoring in Azerbaijan and adjacent territory which carried out since 1998. Unlike our previous studies there are more permanent GPS station and survey mode data aggregated, which accordingly allowed us more accurately determine the dynamics of the main tectonic structures. Eight permanent stations were established by the Institute of Geology and Geophysics since 2006. In 2012, Republican Seismological Survey Center of Azerbaijan National Academy of Sciences started to construct permanent GPS stations, where totally 24 stations were established. Over 35 survey mode sites were measured repeatedly starting from 1998 to 2022. On a broad scale, the GPS velocity field clearly illustrates the NNE motion of Caucasus and adjacent regions with respect to Eurasia south of the Main Caucasus Thrust Fault (MCT). An important note here is the sharp decrease in site velocities, and the clockwise rotation, between sites located to the west of West Caspian Fault (WCF) in Kura Depression and Talish region and sites to the east of WCF in Absheron Peninsula. This decrease and difference in GPS vector directions indicate high strain accumulation rates ~6 mm/yr south to Absheron Peninsula. We believe that the significant accumulation of elastic energy is responsible for the activation of seismic events and of mud volcanoes in this region. Thus, spatial densification of the GPS observations is needed to better resolve localized deformation, and consequently the seismic hazard in the eastern Caucasus, Kur Depression, and Absheron area.
How to cite: Safarov, R., Gadirov (Kadirov), F., Yetirmishli, G., Mammadov, S., Kazimov, I., Floyd, M., Reilinger, R., and King, R.: Crustal deformation of the Azerbaijan territory: results from 25 years (1998 - 2022) of monitoring using GPS, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1950, https://doi.org/10.5194/egusphere-egu25-1950, 2025.
Eight strike-slip earthquake swarms since 2008 in the broader region of Euboea, Phthiotis and Boeotia (central Greece) strongly suggest that the North Aegean Sea shear continues further southwestwards in mainland central Greece. Although most of the swarms are produced by NE-SW-striking dextral faults, as expected, three swarms are produced by the conjugate NE-SW-striking sinistral faults. In fact, one of these occurred in the Greek mainland where extension was considered the dominant stress regime as suggested by previously studied large normal fault zones. GPS strain rates show that dilatation and shear variably coexist, suggesting a transtensional regime. We interpret this seismotectonic setting with the ‘wrench’ tectonic model and the intense accumulated simple-shear deformation deriving from the North Aegean Sea; thus, the dextral faults represent the Riedl shears (R) and the sinistral faults the conjugate Riedl shears (R’). Based on the same model, the co-existence of WNW-ESE-oriented normal faults in the same area can also be explained.
The GPS velocities in the study area revealed increasing values along a NW-SE trending profile, parallel to the Euboea Island axis, in two ways: i) from NW to SE, the profile-normal (NE-SW) component demonstrates stepwise increasing values in station groups on both Euboea and mainland Greece (Phthiotis-Boeotia-Attica, eastern Sterea Hellas), and ii) within these groups, the stations on mainland Greece move faster toward SW than the respective ones on Euboea. These two observations led us to the partitioning of the study area into five compartments, sliding to each other along ‘soft’, NE-SW-trending dextral shear boundaries with increasing rate towards the SE, and a further division of the three middle compartments by the two rifts, i.e. the North and South Euboean Gulfs. This interpretation also agrees with the aforementioned ‘wrench’ model and the NE-SW-oriented shear.
How to cite: Sboras, S., Mouzakiotis, E., Chousianitis, K., Karastathis, V., Evangelidis, C., Lazos, I., Papageorgiou, A., Liakopoulos, S., and Iordanidou, K.: Geodynamic and seismotectonic implications from recent strike-slip earthquake swarms and GPS-based geodetic analysis in Euboea, Phthiotis and Boeotia, central Greece, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5447, https://doi.org/10.5194/egusphere-egu25-5447, 2025.
We analyzed the structure of a fault zone and the age of deformed and displaced sedimentary units to identify recent faulting episodes and reconstruct the rate of young tectonic movements along the western margin fault of the Dead Sea Basin (DSB).
The DSB, one of the most tectonically active areas in the Levant, developed within a step-over zone between two strike-slip segments of the Dead Sea Transform fault. Its margins are bordered by normal and strike-slip faults, forming a pull-apart basin. During the Quaternary, several saline and hypersaline lakes formed within the basin, leading to the deposition of evaporites, including aragonite, gypsum, and halite. Normal fault scarps generate cliffs with elevations of 350–500 m, exposing striated surfaces and fault damage zones along in the western border of the basin. These faults cut through foothill conglomerates, which were cemented by aragonite deposits during periods of high lake levels. Newly formed fault scarps located below the lake level were quickly covered by aragonite cement. Some of these cements, along with stromatolites, were subsequently displaced and striated during newer faulting episodes.
We conducted 15 U-series age determinations on conglomerate cements and aragonite mineralization covering at least five individual fault scarps that displaced upper Pleistocene sediments. The fault scarps exposed in an outcrop of fault zone approximately 30 m wide. The ages of deformed deposits on these fault segment vary between 120 to 263 kyr for the oldest sample, to 18–21 kyr for the youngest one, with several adjacent fault segments being 83 to 51 kyr old. Additionally, conglomerates on a slope yields ages of 141–144 kyr.
Variations in cement ages along different fault surfaces indicate that each fault surface represents a discrete earthquake. By correlating the sedimentary sequence, we determined that the vertical displacement component of 14.5 m between these faults occurred between 83 kyr and 18 kyr before present. This corresponds to surface ruptures of ~1 m per individual earthquake, with an integrated vertical displacement rate of ~0.22 mm/yr.
Previous works in this fault zone suggested that activity since ~6.5 Myr while the entire stratigraphic separation in this area is 0.5-1 km. We therefore conclude that the fault is probably active without changing its location in the last millions of years while the recent subsidence rate is similar, or slightly higher than the integrated rates of 0.07-0.18 mm/yr.
How to cite: Vaks, A., Sagy, A., and Golan, T.: Late Quaternary displacement rate of Dead Sea western marginal fault, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6861, https://doi.org/10.5194/egusphere-egu25-6861, 2025.
The Sea of Marmara represents one of the most critical seismic gaps due to its high fault slip rate (~20 mm/yr), the long interval since the last major earthquake (~250 years), and its proximity to densely populated metropolitan areas. Understanding the complexity of faulting and seismicity in this region is therefore essential. In this study, we utilize a convolutional neural network-based detection and phase picking algorithm (Mousavi et al., 2020) combined with a phase associator employing a grid-search location method (Zhang et al., 2019), significantly increasing the number of detected events using the same dataset as the Kandilli Observatory and Earthquake Research Institute (KOERI) data center (BDTIM) stations. Each waveform is manually reviewed to accurately distinguish real earthquakes from false positives. Furthermore, by incorporating data from AFAD and the local Prince Islands Real-Time Earthquake Monitoring System (PIRES), we construct an accurate and detailed seismicity map of the Sea of Marmara. Our results demonstrate that seismicity patterns can be greatly refined by integrating data from multiple networks and applying state-of-the-art methods for earthquake detection, location, and association. (This study is funded by TÜBİTAK Project No. 121Y407.)
How to cite: Konca, A. O., Can, B., Aktar, M., and Ozakin, A.: Seismicity in the Sea of Marmara Obtained Using Machine Learning Algorithms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7419, https://doi.org/10.5194/egusphere-egu25-7419, 2025.
Apart from conventional geologic methods used to estimate slip rates along active faults, GPS and InSAR have become widely used geodetic techniques for constraining interseismic slip rates in active tectonic studies due to their ability to provide wider spatial coverage. The North Anatolian Fault (NAF), one of the most active transform faults in the world, continues to be a key subject of active tectonic research in Türkiye due to its major seismic activity, which has affected millions of lives. Thus, reliable slip rate estimation is critical for understanding the geodynamics and seismic hazards of the NAF. However, geologic and geodetic slip rates available in the literature show significant differences along the NAF, highlighting the need for further investigations. In this study, the newly published GPS and InSAR velocity fields are modeled within elastic half-space to constrain slip rates along profiles cutting across NAF from Saros Bay to Varto (longitudes between 26° and 42°).
Overall, the results of this study suggest that the deviations between geologic and geodetic slip rates arise mainly from slip partitioning along the secondary segments, particularly in the multi-segmented portion of the NAF in the Marmara Region. Both GPS- and InSAR-derived slip rates show similar trends and are compatible with a locking depth of 10 kilometers, although GPS-derived slip rates tend to be slightly lower than those estimated from InSAR data. From Bolu to Erzincan, slip rates remain relatively stable, ranging from 20–24 mm/year. Along the central segments of NAF, profiles between Gerede and Kargı indicate a transpressional regime transitioning into a transtension west of Niksar, where NAF bends southeastward forming multiple splays. Further east, extension again starts to accompany the strike-slip motion near Erzincan Basin. According to our findings, right-lateral motion along the main strand of NAF drops sharply towards the east just after Erzincan Basin to 16–18 mm/yr and after Karlıova Junction to 10-11 mm/yr around the Varto Fault Zone where the regime becomes transpressional.
Keywords: North Anatolian Fault, GPS, InSAR, geodetic slip rate analysis.
How to cite: Oğuz, R., Oral, D. O., Ayhan, M. E., and Özacar, A. A.: Interseismic Slip Rate Estimations Along the North Anatolian Fault: Insights from GPS and InSAR Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9653, https://doi.org/10.5194/egusphere-egu25-9653, 2025.
The evergrowing geodetic studies in the applications of GPS and InSAR are presenting a great potential to better map out interseismic velocity and strain rate fields in a given region. These methods allow scientists to find ongoing deformation type and rate on active faults with great precision, which is in fact quite important in seismic hazard analyses in the sense of earthquake source characterization. With this purpose, we made a GPS velocity compilation of Türkiye, Greece and other neighboring countries first, then the InSAR derived velocity field was merged to create one combined velocity field of the area, using a least-squares approach. Afterwards, the active strain rate field of Türkiye and its vicinity is calculated using GPS, InSAR and the merged data.
Resultant maximum shear strains derived from GPS data varies between 80 and 180 nstrain/yr along North Anatolian Fault (NAF), which is slightly higher than InSAR based findings ranging between 60 and 140 nstrain/yr. Both results display relatively low shear strains on the locked Marmara segment of NAF and highest values on Ganos, İzmit, Düzce, Bolu and Gerede segments possibly due to the presence of postseismic signals. Towards east, shear strains are lower but InSAR derived ones increase noticeably where NAF curves and branches into multiple fault splays near Niksar.
Resultant anomalies of InSAR based dilational strains suffer from higher degrees of smearing in north-south direction and differ more noticeably. Especially, InSAR indicates elevated and widespread dilations throughout Thrace Basin and Karlıova Junction that contradicts the GPS derived strains, possibly due to temporal variations. Western Anatolia and İskenderun Gulf are represented by large positive dilational strains in both datasets which suggest relatively fast active extension. In Western Anatolia, Menderes and Gediz grabens are both characterized by high amounts of dilation that reaches up to a maximum of 80 nstrain/yr at the western section of Menderes Graben.
Principal strain directions computed from GPS and InSAR are similar within fast deforming areas but differ largely at areas where strains are minimal such as Central Anatolia which implies reduced precision in slowly deforming zones. All in all, strain rate field obtained from GPS compilation shows better fit with mapped active faults and earthquake mechanisms. Thus, resultant strain rate field estimations using only InSAR data shall be used with caution and rather be combined with sufficient number of GPS recordings if applicable.
Keywords: GPS, InSAR, Interseismic Strain Field, Shear Strain, Dilation, Eastern Mediterranean
How to cite: Oral, D. O., Özacar, A. A., and Ayhan, M. E.: Comparative Analysis of Geodetic Strain Rate Field Around Anatolia: GPS vs InSAR Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11508, https://doi.org/10.5194/egusphere-egu25-11508, 2025.
The two major earthquakes (magnitude 7.8 and 7.6) in southeastern Turkey in 2023 resulted in a combined fault rupture length of 500 km. The events were driven by the northward motion of the Arabian Plate colliding with the Eurasian Plate and the westward escape of the Anatolian Plate. The coseismic deformation field revealed a predominantly left-lateral strike-slip motion in both earthquakes. In addition to coseismic studies, research into postseismic relaxation processes provides critical insights into fault properties, as well as the deep structure of the lower crust and upper mantle, offering valuable support for understanding the regional tectonics and fault dynamics.
We use Interferometric Synthetic Aperture Radar (InSAR) and Sentinel-1 data to analyze the surface deformation over a 20-month postseismic period following the earthquakes. To comprehensively cover the affected area, we collected data from three ascending and three descending Sentinel-1 tracks, each comprising 4-5 consecutive frames. In total, we processed SAR data from 28 frames with approximately 50 temporal samples. Using the SIGMA approach developed by our team, we derived time-series displacement results. We further integrated GNSS data with the DetrendInSAR method, enabling the correction of atmospheric delays and the unification of displacement reference across multiple tracks. Neglecting the north-south component in the InSAR line-of-sight observations, we decomposed the ascending and descending data to derive the east-west and quasi-vertical displacement time series. The results reveal that the east-west displacement field displays both shallow near-fault afterslip signals and large-scale deformation signals far from the fault, indicating that the postseismic process involves not only shallow afterslip but also deep viscoelastic relaxation. The vertical displacement results show significant subsidence and uplift, consistent with surface deformation characteristics caused by deep viscoelastic relaxation.
By processing postseismic SAR data from the 2023 Turkey earthquakes, this study elucidates the characteristics of surface deformation in the aftermath of the events. Through postseismic modeling, it further uncovers key parameters of the subsurface structure and fault slip behavior in the study area, contributing significantly to our understanding of the dynamics of the Anatolian Plate.
How to cite: Liu, J. and Jónsson, S.: InSAR Postseismic Displacements of the 2023 Turkey Earthquakes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11616, https://doi.org/10.5194/egusphere-egu25-11616, 2025.
The study of young active faults provides an important opportunity to constrain the early phases of fault growth and linkage. In addition, such structures often pose an underestimated seismic hazard as they can have limited geomorphic and structural expression. The Aigion - Erineos fault system (AEFS) is a young active normal fault on the south coast of the Gulf of Corinth rift zone in Central Greece that provides a key link between the Gulfs of Corinth and Patras. However, significant uncertainties remain regarding the key characteristics of this fault system, including its geomorphic expression, throw, slip rate, age and the degree to which its constituent fault segments are linked. Here we combine geomorphic field observations and structural measurements, DEM and topographic analyses, short-interval ground motion data, and offshore seismic data to produce the most complete characterisation of the AEFS to-date. Our findings show a complex geomorphic expression of the AEFS with 5 active fault segments, arranged in an en-echelon structure and partially to fully linked together. We show the Aigion Fault segment (AF) has an initiation age of 200-240 ka, but there has been a significant increase in slip rate since 80 ka. Consequently, we suggest the AF has a slip rate of ca. 5-6 mm/yr, greater than the time-averaged rate estimated by McNeill et al., 2007 of 3.5 ± 1 mm/yr. Data from the European Ground Motion Service (EGMS) illustrate that the field derived fault traces of the AEFS correspond closely with an abrupt, linear transition from uplift to subsidence seen from satellite measurements, suggesting the possible presence of ongoing aseismic deformation. The three fault segments to the west of the AF (the Fassouleika, Selianitika, Erineos segments) are suggested to have initiated after 80 ka and may be as young as 25 ka and are now partially to fully linked with the AF. We obtain maximum slip rates for these segments of between 5 and 9 mm/yr. To the east an offshore fault segment is likely to be soft-linked with the AEFS and has a well constrained slip rate of 2.7 mm/yr through the Holocene. Our results suggest the linked fault system has a total length of ca. 20 km, with a potential maximum credible earthquake size of Mw = 6.6.
How to cite: Whittaker, A., Hook, J., and Bell, R.: New constraints on the activity and evolution of the young Aigion-Erineos Fault System, Gulf of Corinth, Greece, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11625, https://doi.org/10.5194/egusphere-egu25-11625, 2025.
Large-magnitude strike-slip earthquakes can cause extensive surface ruptures that stretch hundreds of kilometres. High-resolution mapping of these ruptures provides insights into the location of the rupture strands, coseismic displacements and geometrical complexities that are vital to understanding earthquake rupture processes and fault zone hazards. The February 6, 2023, Kahramanmaraş Earthquake, the most destructive earthquake in Türkiye, reactivated the East Anatolian and Dead Sea Fault zones and created a 350 km long surface rupture with a maximum displacement of ~8 m.
In this study, we acquired optical and thermal imagery strips using an Unmanned Aerial Vehicle (UAV) system along 320 km of the surface rupture. The width of the strip is 300 m. The data were preprocessed (RJPG to TIFF conversion), the temperature anomalies in the thermal images obtained compared to the surroundings of the surface rupture were mapped, and the thermal-based surface rupture map was confirmed with high-resolution (10 cm) optical images.
Generally, optical or radar satellite imagery is widely used to map earthquake surface ruptures, but their resolutions are limited to a maximum of 0.5 m and 12 m, respectively. These resolutions can be increased ten times by the pixel offset tracking. However, there are still issues with locating rupture strands precisely and quantifying coseismic displacement accurately, especially on-fault displacements. The recent developments in Unmanned Aerial Vehicle (UAV) technologies allow for the mapping of earthquake surface ruptures with a very high resolution (e.g., <10 cm) along very long distances (e.g. 30 km per day). One of the issues with most UAV systems with only an optical camera is tracing surface rupture correctly under vegetation cover (e.g. forest, grassland) and rugged surfaces with different slope aspects.
A UAV equipped with a thermal and optical camera was deployed to address this issue, enabling comprehensive data collection and analysis. While surveying, we used real-time optical and thermal imaging to trace surface rupture and test the effectiveness of thermal imaging. This approach enabled the identification of surface fractures that are not visible in optical images because the thermal signature of the rupture is more vivid than in optical images. This signature is relative temperature differences compared to the surrounding area due to the changing humidity and micro-topography of the surface because of shearing. Using thermal imagery provides two advantages: incrementally improves the tracing of surface rupture while the UAV acquires the data in the field, especially under different vegetation covers. So, it provides extra guidance to UAV pilots to trace strands of the earthquake surface rupture. The second advantage is that it facilitates the mapping of surface rupture in the lab when optical imagery cannot be used to trace surface rupture for several reasons (e.g., vegetation, sunlight, ploughing, and topographic shadow). As the first application of thermal imaging on earthquake surface rupture mapping, our findings demonstrate the advantages of thermal imaging, especially in forested and agricultural areas where conventional optical methods fall short. Integrating thermal data with optical provides key insights for improving mapping accuracy in surface rupture areas, significantly advancing earthquake research.
How to cite: Karakaş, M., Özcan, O., Yıldırım, C., Akay, S. S., Gedik, Y., and Baka, Ç. M.: High-Resolution Thermal Imaging of the Surface Rupture of the February 6 2023, Kahramanmaraş Earthquake (Mw 7.8), Türkiye, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11894, https://doi.org/10.5194/egusphere-egu25-11894, 2025.
In November 2020, an earthquake sequence started to evolve ca. 10 km east of Thebes (Boeotia, central Greece) with a maximum magnitude of ML4.4 (02/12/2020). In July 2021, the seismic activity migrated westwards, under the town of Thebes. Before the activity faded away completely, a new outburst started in March 2022. The whole activity sparsely continued until the first quarter of 2023. In total, 5 earthquakes of 4.0≤ML≤4.4 occurred during the seismic crisis. Published focal mechanisms of the strongest events revealed normal faulting on E-W- to WNW-ESE-striking nodal planes.
A few years before this episodic seismic activity near Thebes, a morphotectonic field mapping and analysis were carried out in the broader area. In more particular, within the epicentral area, two fault groups were detected: i) the ‘Kallithea’ fault zone, i.e. a series of two aligned SSW-dipping normal fault segments, and ii) the ‘Thebes’ fault system of parallel to subparallel, occasionally imbricated, roughly E-W-striking oblique-normal faults dipping to the South.
The Kallithea fault segments separate the two rather elongated hills of alpine carbonates from the Neogene basinal deposits (including Holocene slope debris). Slickenlines preserved on mildly eroded limestone free-faces show quasi-pure normal faulting in a NNE-SSW trending extensional stress field. Morphometric analysis along the fault zone suggests that the two segments are not yet linked to each other, reducing significantly the earthquake potential of the fault zone.
The Thebes fault system has formed a subdued topographic relief on Plio-Pleistocene and Pliocene deposits demonstrating variable throws on the overstepping faults array at the order of 1-2 m, producing a total stepwise downthrow of the hanging-wall of about 15-20 m. Although the lithology does not allow a good preservation of free-faces, few exposures bear oblique slickenlines revealing a ca. N-S direction of extension. This fault system is probably the surficial manifestation of a single deeper structure.
Both fault groups are considered responsible for the 2020-2023 seismic crisis, transferring stresses from one to the other as also suggested by the episodic activity and the horizontal migration of the epicentres. In fact, the northwestern segment of the Kallithea fault zone is probably associated to the eastern cluster of the seismic activity, also suggesting a further northwestward continuation of the fault segment. The surficial length of the specific faults suggests moderate expected magnitudes, although strong historic and early instrumental earthquakes have been recorded in the surrounding area.
How to cite: Georgiou, C., Sboras, S., and Rondoyanni, T.: Morphotectonic investigation of the active faults in Boeotia, central Greece, before the 2020-2023 seismic crisis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12357, https://doi.org/10.5194/egusphere-egu25-12357, 2025.
This study investigates the second event of an earthquake doublet that struck Türkiye with magnitudes Mw 7.7 and Mw 7.6, on February 6, 2023. While space-based geodetic and remote sensing studies have provided information on surface rupture and slip distribution, field-based data on coseismic deformation, slip distribution, and fault sections are lacking. We generated high-resolution (10 cm) low-altitude UAV imagery to address this gap and created a continuous 300-m-wide strip map along the entire surface rupture length. Our mapping reveals a primarily sinistral rupture length of approximately 143 km between Göksun and Gözene, with previously unrecognized faults at the westernmost 4.5 km and easternmost 20 km. The rupture is divided into six major sections: Göksun, Ericek, Ekinözü, Barış, Nurhak Fault Complexity, Kullar, and Gözene. The width of the deformation zone varies from a few meters to 1.5 km along these sections, with narrower and more localized zones in the Göksun, Ekinözü, and Barış sections, and wider zones in the Ericek Section and the Nurhak Fault Complexity Section. Our analysis of 553 coseismic displacements (including 55 off-fault and 4 right-lateral) reveals maximum slips of 10.58 ± 0.3 m in the Ekinözü section. The average moving means coseismic displacement is 4.08±0.73 m, with a spatial distribution showing long-wave variability separated by a large restraining stepover at the Nurhak Fault Complexity. These findings provide crucial insights into the coseismic deformation and slip distribution of the second earthquake, enhancing our understanding of the rupture mechanics and contributing valuable field-based data for seismic hazard assessment in the region
How to cite: Yildirim, C., Ozcan, O., Akah, S. S., Sarıkaya, M. A., Karakaş, M., Gedik, Y., Kozacı, Ö., Altunel, E., Clahan, K., and Koehler, R.: High-Resolution Co-seismic Surface Displacement Distribution for February 6, 2023, Elbistan (Kahramanmaras) Earthquake, Turkiye , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15645, https://doi.org/10.5194/egusphere-egu25-15645, 2025.
The coastline shape is continuously changed by natural events such as tectonic movements, subsidences, and erosion. All these changes are of great importance for understanding the dynamics of the coastal systems and their responses against events. These changes, emerging from the past to the present for various reasons, therefore form a guiding background for management and decision-making activities related to coasts in the future. In this study, Lake Gölbaşı in Adıyaman was investigated within the East Anatolian Fault Zone (EAFZ). One of the main branches of EAFZ passes directly through the Gölbaşı district. The Mw 7.8 Kahramanmaraş earthquake that occurred on February 6, 2023, caused severe land deformations, serious changes in the coastline, and land subsidence in the region. In addition to the morphological changes of the coastline, such effects as land subsidence are important in understanding how tectonic forces shape the coastal environment. Such analyses reveal the effects associated with sediment transport, erosion, long-term coastal dynamics, and changes in water levels. This information can be an important guide in predicting future tectonic events and environmental impacts and in risk management. Firstly, we performed InSAR time series analysis to obtain time-dependent deformation maps using Sentinel-1 and COSMO-SkyMed radar data. Publicly available Sentinel-1 data, operating in the C band, provides sufficient information for analyzing large-scale deformations. In contrast, high-resolution X-Band COSMO-SkyMed data, obtained from the Kahramanmaraş Supersite, enables the detection of smaller-scale changes. Additionally, optical satellite data from Sentinel-2A is employed to examine subtle morphological changes in the Gölbaşı Basin. While radar data excels at detecting specific deformations, optical data offers a broader perspective on environmental changes. By integrating these tools, the study provides valuable insights into the dynamic changes occurring in the area. The study covers a time series from February 2022 to February 2024, allowing for the analysis of both pre- and post-earthquake coastline changes and assessment of the spatial and temporal characteristics of these changes in relation to the active fault line by Lake Gölbaşı and surroundings. Our findings highlight the urgent need to address challenges related to improving living conditions, disaster risk reduction, and ecological protection. These insights are essential for developing practical and sustainable long-term strategies for natural hazard risk management.
How to cite: Uçar, A., Ergintav, S., and Uçarkuş, G.: Assessing Coastline Changes of Lake Gölbaşı (Adıyaman, Türkiye) Through InSAR Time Series Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17404, https://doi.org/10.5194/egusphere-egu25-17404, 2025.
The Pütürge segment of the East Anatolian Fault (EAF) represents a critical link in the tectonic framework of the region. The northeastern end of this segment ruptured during the 2020 Sivrice earthquake (Mw 6.8), while the southwestern end marked the termination of the 2023 Kahramanmaraş earthquakes (Mw 7.7, Mw 7.6). Between these two events, the segment remained a notable seismic gap until the Mw 6.0 earthquake on October 16, 2024.
This study utilizes GNSS and InSAR data to examine the deformation dynamics of the Pütürge segment before and after the 2024 earthquake. While the extent of rupture during the October event remains unclear, preliminary geodetic analyses provide valuable insights into strain accumulation, potential creep activity, and coseismic deformation patterns.
Our findings contribute to understanding the seismic behavior of the Pütürge segment, emphasizing its importance in seismic hazard assessments and the broader tectonic setting of the East Anatolian Fault.
How to cite: Özarpacı, S., Doğan, U., Ergintav, S., Çakır, Z., Zabcı, C., Özdemir, A., Ayruk, E. T., Farımaz, İ., Turğut, M., Beytut, B. B., and Köküm, M.: Seismic Activity and Deformation of the Pütürge Segment of the East Anatolian Fault: Insights from Recent Earthquakes and Geodetic Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18264, https://doi.org/10.5194/egusphere-egu25-18264, 2025.
