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Earthquake hypocenter locations and depth cross-sections. Green dots represent hypocenter locations from AFAD catalog, red dots represent hypocenter locations from KOERI catalog. Black dots represent the hypocenter locations re-located by combining the entire data from KOERI and AFAD seismic networks.
Source publication
Turkey is located in a seismically active region with a complex tectonic history. In order to perform seismic risk assessment precisely, major fault zones (North Anatolian Fault Zone and East Anatolian Fault Zone) that are well defined are monitored continuously. It is a widely known fact that intraplate settings, such as Anatolian Plate, in which...
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Citations
... To investigate the validity of the hypothesis on the supershear rupture transition, Rosakis et al. (2023) performed computations: the authors assumed V s = 3320 m/s and V p = 5780 m/s, which is in a good agreement with the velocity models for the southern Turkey region (Acarel et al., 2019). Then, the Rayleigh wave speed is V R = 3050 m/s, and the rupture propagation speed is V r = 4960 m/s. ...
... As a result, the estimated depth was 8-10 km. Thus, both earthquakes occurred in the upper part of the Earth's crust, where the P-and S-wave velocities are approximately 5.8 and 3.3 km/s, respectively (Acarel et al., 2019). The values of the normalized residual function (ε) for the source models of the earthquakes under study in the instantaneous point source approximation were 0.391 and 0.305 for the first and second events, respectively. ...
... In particular, for the first of them (Melgar et al., 2023), a value of 3.2 km/s was obtained and according to (Mai et al., 2023), the rupture propagated in a southwest direction at a velocity of about 2.0 km/s and, in the northeast, from 2.5 to 3.0 km/s. This means that the rupture velocities (V r ) obtained in these works are lower than the S-wave velocities (V s ) (Acarel et al., 2019). This is also confirmed by the results of (Delouis et al., 2023), indicating that, for most of the fault, V r < V s and, only in small areas between different segments, V r > V s . ...
... We assume a constant rupture velocity for simplicity. We utilize synthetic Green's functions in the entire frequency range, considering a 1D regional velocity model by Acarel et al. 31 with added shallow low-velocity layers to account for high-frequency amplification of a generic rock site; see Methods and Supplementary Fig. S6 for results with the original velocity model of Acarel et al. 31 . ...
... We assume a constant rupture velocity for simplicity. We utilize synthetic Green's functions in the entire frequency range, considering a 1D regional velocity model by Acarel et al. 31 with added shallow low-velocity layers to account for high-frequency amplification of a generic rock site; see Methods and Supplementary Fig. S6 for results with the original velocity model of Acarel et al. 31 . ...
... Hz is applied to the real instrumentally corrected seismograms and synthetics, and both are integrated into displacements. We use synthetic full-wavefield Green's functions in the velocity model of Acarel et al. 31 see section Crustal velocity model. Moment-rate of each subevent is a triangular function of 20-s duration. ...
Damages due to large earthquakes are influenced by broadband source effects that remain enigmatic. Here we develop a broadband (0–10 Hz) source model of the disastrous 2023 Mw7.8 Kahramanmaraş, Türkiye, earthquake by modeling recordings of 100 stations. The model combines coherent and incoherent rupture propagation at low and high frequencies, respectively. We adopt a planar 300 km long kinked fault geometry from geology and pre-constrain the slip model from seismic and geodetic data. We demonstrate that the southwestward rupture propagation was delayed by ~15 s and that the observed strong waveform pulses can be explained by the directivity effect due to a specific combination of the coherent and incoherent components. We show that even a rough estimate of major rupture parameters makes the ground motion simulations of such large events possible, and may thus improve the efficiency of rapid, physics-based, shaking estimation for emergency response and seismic hazard assessment.
... The westward rupture speed of 3.6 km/s is very close to the local shear wave speed of 3.3-3.5 km/s (refs. 3,15 ), and supershear rupture might occur on parts of the west Sürgü Fault. Faster western rupture is reported in the slip model by Melgar et al. 16 , in which a maximum rupture speed of 4.8 km/s is preferred. ...
On February 6, 2023, an Mw7.8 earthquake hit the East Anatolian Fault (EAF) and Narlı Fault (NF), followed by an Mw7.5 event on the Sürgü Fault. We combine multiple seismic datasets, global navigation satellite system recordings, and radar satellite images with finite fault inversion and slowness enhanced back-projection to study the rupture kinematics. Our analysis reveals that the rupture originated on the NF, propagating 120 km northeast at 3.05 km/s and 200 km southwest at 3.11 km/s after reaching the EAF junction, exhibiting overall subshear speeds. Further Mach wave analysis confirms the subshear rupture, matching the prediction using close-Rayleigh speeds. The unexpectedly-large slip on some EAF segments suggests a supercycle lasting ≥900 years. The EAF geometry is similar to the San Andreas-San Jacinto Fault system, while the latter has higher slip rates but without large earthquakes on its southern segments since 1857, carrying the potential of an M8 earthquake.
... The M7.8 Kahramanmaraş/Pazarcik earthquake was, by many measures, bigger and more destructive than what had been expected based on historical records in the past several centuries [4]. The estimated magnitude of the largest earthquake that occurred on the East Anatolian Fault (EAF) in the last few hundred years is 7.2 which is believed to be either the 1789 Palu (Elazıg) earthquake or the 1872 Amanos earthquake [5][6][7]. ...
... Sub-Rayleigh to Super-shear To constrain the model, first we consider the tectonic stress state in the region. Prior studies suggest that the angle of maximum compressive stress is in a N16.4°E compression regime (σ 1 ) [4]. Based on this maximum horizontal stress direction, we show in the Appendix Figure B2, that the ratio of the resolved shear stress to the normal stress on any fault segment is particularly sensitive to the choice of relative principal stresses magnitudes. ...
The 2023 M7.8 Kahramanmara\c{s}/Pazarcik earthquake was larger and more destructive than what had been expected. Here we analyzed near-field seismic records and developed a dynamic rupture model that reconciles different currently conflicting inversion results and reveals spatially non-uniform propagation speeds in this earthquake, with predominantly supershear speeds observed along the Narli fault and at the southwest (SW) end of the East Anatolian Fault (EAF). The model highlights the critical role of geometric complexity and heterogeneous frictional conditions in facilitating continued propagation and influencing rupture speed. We also constrained the conditions that allowed for the rupture to jump from the Narli fault to EAF and to generate the delayed backpropagating rupture towards the SW. Our findings have important implications for understanding earthquake hazard and guiding future response efforts and demonstrates the value of physics-based dynamic modeling fused with near-field data in enhancing our understanding of earthquake mechanisms and improving risk assessment.
... We locate 57 and relocate the 13,585 PAL detections with hypoInverse (Klein, 2002) and hypoDD (Waldhauser,58 manuscript submitted to Earthquake Science 2001), respectively. Table 1 shows the 1D velocity model used for location purpose, which is 59 modified from Güvercin et al. (2022) and Acarel et al. (2019) that minimizes the average residual 60 on stations along the EAF ( Figure S3). In hypoInverse, we weigh different phases by the epicentral 61 distance, time residual, and type of phase. ...
We build a high-resolution early aftershock catalog for the 2023 SE Türkiye seismic sequence with PALM, a seamless workflow that sequentially performs phase Picking, Association, Location, and Matched filter for continuous data. The catalog contains 29,411 well-located events in the two mainshocks rupture region during 2023/02/01-2023/02/28, which significantly improves the detection completeness and relocation precision compared to the public routine catalog. Employing the new PALM catalog, we analyze the structure of the seismogenic fault system. We find that the Eastern Anatolian Fault (EAF) that generated the first Mw 7.9 mainshock is overall near-vertical, whereas complexities are revealed in a small-scale, such as subparallel subfaults, unmapped branches, and stepovers. The seismicity on EAF is shallow (<15 km) and concentrated in depth distribution, indicating a clear lock-creep transition. In contrast, the Sürgü Fault (SF) that is responsible for the second Mw 7.8 mainshock is shovel-shaped for the nucleation segment and has overall low dip angles (~40-75°). Aftershocks on the SF distribute in a broad range of depth, extending down to ~35 km. We also analyze the temporal behavior of seismicity, discovering no foreshocks preceding the first mainshock, and no seismic activity on the SF before the second mainshock.
... The Malatya-Ovacık Fault Zone (MOFZ) is one of these strike-slip structures, which was suggested to have marked the eastern boundary of Anatolia of about 5 Ma ago but to bein active today based on early kinematicmodels (Westaway and Arger, 2001;Westaway et al., 2008). However, recent geodetic (Aktuğ et al., 2013a;Aktuğ et al., 2013b;Özener et al., 2020), structural (Kaymakçı et al., 2006), palaeoseismological (Sançar et al., 2019;Yazıcı et al., 2021), geomorphological (Yazıcı et al., 2018;Sançar et al., 2020) and seismological (Acarel et al., 2019) studies show the opposite yielding significant tectonic activity along the MOFZ. ...
... Key to lettering: GNSS, Global Navigation Satellite System; EAF, East (Sançar et al., 2019;Yazıcı et al., 2021) and structural data (Kaymakçı et al., 2006) clearly support an ongoing tectonic activity along the OF and MF. Moreover, microseismic activity close to the junction of the OF and MF (Acarel et al., 2019), and local global navigation satellite system (GNSS) measurements covering the region (Aktuğ et al., 2013a;Aktuğ et al., 2013b;Özener et al., 2010) indicate a larger strain accumulation along these structures than previously estimated. The GNSS-based elastic block model slip rates are 1.2 ± 0.3 mm/a and 1.6 ± 0.3 mm/a (Aktuğ et al., 2013a) or 1.8 ± 0.1 and 1.2 ± 0.1 mm/a (Aktuğ et al., 2013b) for two distinct members of this fault zone, the OF and MF, respectively. ...
... Although the main boundary elements, the NASZ and EASZ, were thought to be responsible for sharing almost all deformation during the westward extrusion of the Anatolia, our slip-rate estimates and recent multidisciplinary studies (e.g., Özener et al., 2010;Aktuğ et al., 2013a;Aktuğ et al., 2013b;Yıldırım, 2014;Higgins et al., 2015;Sarıkaya et al., 2015;Sançar et al., 2019;Acarel et al., 2019;Yıldırım et al., 2016;Yazıcı et al., 2018;Sançar et al., 2020;Yazıcı et al., 2021;Özbey et al., 2022) show that there is remarkable internal deformation within this continental piece. The MOFZ is only one of the strike-slip faults of many others, which partly share the total internal strain. ...
The active tectonics of Anatolia is mostly characterized by its westward motion with respect to Eurasia between the Hellenic subduction in the west and Arabia-Eurasia continental collision in the east. Although most of the deformation is suggested to be confined along Anatolia?s boundary elements, viz. the North and East Anatolian shear zones, recent studies indicate a higher magnitude of internal strain accumulation, especially along the parallel/subparallel strike-slip faults of its central province. We present the first morphochronology-based slip rate estimate for one of these strike-slip structures, the Ovacık Fault, by using cosmogenic 36Cl dating of offset fluvial deposits. At the Köseler Site (39.3643°N, 39.1688°E), two faulted risers, bounding the alluvial fan with its subplanar surface (NF1/NF1') and the inset terrace tread (NF1/T2), are offset 19-24 and 15-22 m, respectively. The scattered surface ages and variability of 36Cl concentrations in depth profiles suggest strong evidence for inheritance in alluvial fan and terrace deposits; thus, we used modelled depth-profile ages for both surfaces. The modelled ages 8-10 ka for NF1 and 6?8 ka for T2 yield slip-rate estimates 2.4 +0.5/-0.4 mm/a and 2.8 +0.7/-0.7 mm/a, respectively, for the upper-tread reconstruction of the NF1/NF1' and the lower-tread reconstruction of the NF1/T2. Our results together with previous slip-rate estimates for other structures show a significant internal deformation for Anatolia, especially along its subparallel strike-slip faults. These secondary faults slice Anatolia into several pieces giving rise to the formation of the Malatya-Erzincan, Cappadocian, and Central Anatolian slices, where the geometry is strongly controlled by the distribution of the Tethyan accretionary complexes.
... The sequence of events resulted in catastrophic levels of destruction with substantial humanitarian and financial losses. Based on historical records, the magnitude of the event and the total rupture length were both much larger than expected for such a tectonic setting in southern Turkey [3]. This together with the intensity of the measured ground shaking motivated us to investigate the nature of rupture initiation, propagation, as well as the possibility of early supershear transition. ...
... To investigate the validity of this hypothesis, related to supershear transition and the location of TK:4615, we present a preliminary analysis by comparing the location of the station to our independent estimate of obtained from the twin stations record shown in Figure 2a. In order to do this, we assume m/s, and m/s which correspond to a Poisson's ratio of , and are in good agreement with velocity models for the southern Turkey region [3]. It follows then that m/s and m/s. ...
The Mw 7.8 Kahramanmara\c{s} Earthquake was larger and more destructive than what had been expected for the tectonic setting in Southeastern Turkey. By using near-field records we provide evidence for early supershear transition on the splay fault that hosted the nucleation and early propagation of the first rupture that eventually transitioned into the East Anatolian fault. The two stations located furthest from the epicenter show a larger fault parallel particle velocity component relative to the fault normal particle velocity component; a unique signature of supershear ruptures that has been identified in theoretical and experimental models of intersonic rupture growth. The third station located closest to the epicenter, while mostly preserving the classical sub-Rayleigh characteristics, it also features a small supershear pulse clearly propagating ahead of the original sub-Rayleigh rupture. This record provides, for the first time ever, field observational evidence for the mechanism of intersonic transition. By using the two furthest stations we estimate the instantaneous supershear rupture propagation speed to be ~ 1.55 Cs and the sub-Rayleigh to supershear transition length to be around 19.45 km, very close to the location of the station nearest to the epicenter. This early supershear transition might have facilitated the continued propagation and triggering of slip on the nearby East Anatolian Fault leading to amplification of the hazard. The complex dynamics of the Kahramanmara\c{s} earthquake warrants further studies.
... We carefully select 470 well-located earthquakes in the region with root mean squared (RMS) misfit of the solution ≤0.5 s and azimuthal gap ≤180 • , respectively. The recent model of Acarel et al. (2019) is used as the initial model since it is the closest model to the reservoir area. By perturbing velocities in the ±0.3 km/s range, randomly 500 synthetic velocity models are ...
Reservoir-triggered seismicity has been observed near dams during construction, impoundment, and cyclic filling in many parts of the earth. In Turkey, the number of dams has increased substantially over the last decade, with Atatürk Dam being the largest dam in Turkey with a total water capacity of 48.7 billion m³. After the construction of the dam, the monitoring network has improved. Considering earthquakes above the long-term completeness magnitude of MC = 3.5, the local seismicity rate has substantially increased after the filling of the reservoir. Recently, two damaging earthquakes of Mw 5.5 and Mw 5.1 occurred in the town of Samsat near the Atatürk Reservoir in 2017 and 2018, respectively. In this study, we analyze the spatio-temporal evolution of seismicity and its source properties in relation to the temporal water-level variations and the stresses resulting from surface loading and pore-pressure diffusion. We find that water-level and seismicity rate are anti-correlated, which is explained by the stabilization effect of the gravitational induced stress imposed by water loading on the local faults. On the other hand, we find that the overall effective stress in the seismogenic zone increased over decades due to pore-pressure diffusion, explaining the enhanced background seismicity during recent years. Additionally, we observe a progressive decrease of the Gutenberg-Richter b-value. Our results indicate that the stressing rate finally focused on the region where the two damaging earthquakes occurred in 2017 and 2018.
... Aftershock relocated focal depths range from 7-17 km whereas centroid depths from waveform modeling are 2-13 km (inset to Figure 2c). Use of an alternative velocity model (Acarel et al., 2019) increased waveform model centroid depths by on average ∼2 km, reducing but not eliminating this discrepancy. These results mimic relations observed in comparably instrumented regions elsewhere (Gaudreau et al., 2019;Karasözen et al., 2016Karasözen et al., , 2018 and likely reflect the depth resolution limitations of both methods, together with the propensity for earthquakes to nucleate deeper within the seismogenic zone and rupture upward. ...
Plain Language Summary
We investigate the 2020 Mw 6.8 Elazığ (Turkey) earthquake, the largest along the East Anatolian Fault (EAF) in over a century. Anatolian faults are emblematic within the earthquake science community, but most attention has focused on the North Anatolian fault which ruptured repeatedly during the twentieth century, and relatively little is known about the EAF. We use satellite geodesy and seismology to map fault motions during the earthquake, after the earthquake, and in its aftershock sequence. Documenting relations between this earthquake, previous earthquakes, and early postseismic deformation is pivotal to gain a better understanding in what drives rupture behavior. Our results show that previous structural models of the EAF were only partially successful in predicting the end points of the 2020 rupture and that many aspects of this earthquake are characteristic of structurally immature faults. These results are important for seismic hazard assessment in this region.
