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On February 6, 2023, southeastern Türkiye experienced a devastating earthquake doublet along the East Anatolian Fault (EAF), with moment magnitude (MW) values of 7.8 and 7.5. These strong earthquakes resulted in at least 50,000 deaths and severe economic losses. Systematic research on coseismic surface ruptures induced by these events is vital for assessing the cascade rupture behaviors of plate boundary faults and future seismic hazards in the region. Interpretation of high-resolution post-earthquake satellite images and field investigations yielded the following results: (1) the two strong earthquakes had separate rupture zones. The first earthquake generated an approximately 280 km coseismic surface rupture along the south-western segment of the main EAF, with 241 left-lateral displacements reaching up to 6.8±0.68 m, particularly 40 km northeast of the epicenter. The second earthquake produced a roughly 110 km surface rupture on an east-west branch of the EAF, with maximum displacements of 7.2±0.72 m. (2) The MW7.8 earthquake resulted in a cascading rupture across multiple segments of the southwestern section of the main EAF, with significantly variable displacements. The northeastern and southwestern parts of the main EAF and Malatya Fault remain at risk of strong earthquakes in the future. (3) The EAF rupture zone is densely populated, and due to the site amplification effect of loose sediments on foreland alluvial fans, foundation failures of buildings in the populated areas are common. Therefore, it is crucial to enhance the future seismic fortification capabilities in urban and rural areas along the EAF. [ABSTRACT FROM AUTHOR]

The East Anatolian Fault System has been intensively studied over the years due to its potential to generate strong earthquakes and the high exposure of the economy and population in the region. This interest intensified even more after the strong earthquakes in the area at the beginning of February 2023, leading to a focused search for features and precursors that might suggest such an upcoming event. We analyze certain characteristics of seismicity within the East Anatolian Fault System before the earthquakes of February 6, 2023, with magnitudes Mw = 7.8 and Mw = 7.5, over the time period between 1983 and 2022. The earthquake catalog from January 1983 to September 2023, created by Turkish Bogazici University KOERI, is used. Processing of the data is performed by the ZMAP 7.1 software used in the MATLAB environment. Events with a magnitude greater than 2.5 are considered in four time periods: 1983–1992, 1993–2002, 2003–2012, and 2013–2022, totaling 29,346 events. The b-value of the magnitude-frequency distribution of earthquakes (slope of the recurrence graph) is determined; the parameter β, indicative of the increase or decrease in the rate of anomalous seismicity, and parameter Z, associated with anomalous seismic quiescence, is evaluated. A significant decrease in the value of b (from 1.07 to 0.84) is observed when comparing the two periods (2013–2017/2018–2022), indicating accumulated stress in the Earth's crust. Furthermore, the Z parameter analysis for the period July 2021 to December 2022 shows evidence of relative seismic quiet in the examined area compared to the period from January 2020 to the end of June 2021. Those results suggest that the spatiotemporal variations of the studied seismic parameters could serve as predictors of the two very strong seismic events in the southern part of the Eastern Anatolian region of Turkey. [ABSTRACT FROM AUTHOR]

On February 6, 2023, two catastrophic earthquakes occurred on the East Anatolian Fault. The earthquakes had magnitudes of Mw = 7.7 and 7.6 and struck Kahramanmaraş-Pazarcık and Kahramanmaraş-Elbistan, respectively. The Kahramanmaraş-Pazarcık earthquake was triggered at 04:17 local time on the Dead Sea Fault (a branch of the East Anatolian Fault). The last earthquake on the addressed fault occurred about 500 years ago. The recorded peak ground acceleration (PGA) at the Pazarcık station reached 2.05g. In addition, the Pazarcık earthquake triggered two independent earthquakes, the Nurdağı and Islahiye earthquakes, which occurred 10 min later than the Pazarcık earthquake. However, the last earthquake, with its epicenter in Kahramanmaraş-Elbistan, struck at 13:24 local time. The recorded PGA for the Elbistan earthquake is 0.68g. This study aims to present the fault rupture mechanism of the February 6, 2023, Kahramanmaraş earthquakes, earthquake characteristics, and to evaluate the performance of masonry dwellings during the Kahramanmaraş earthquake doublet, which affected 10 provinces and numerous towns and villages. This paper also aims to illustrate the damage and failure mechanisms of the masonry dwellings, despite unexpectedly high accelerations that exceeded the design spectrum in the field, specifically in Kahramanmaraş, Gaziantep, Hatay, and Malatya, according to the current earthquake code in use. [ABSTRACT FROM AUTHOR]

Objective On February 6, 2023, double strong earthquakes of MW7.8 and MW7.5 occurred consecutively within 10 hours in the Kahramanmaraş province in central-southern Turkey. After these double-strong earthquakes, domestic and foreign seismologists studied coseismic surface deformation using field measurements, GNSS, and differential InSAR methods. However, owing to the limitations in the techniques employed, the current coseismic surface deformation results suffer from low spatial resolution and missing data near fault surface ruptures. This study aims to address these limitations and comprehensively present the coseismic surface deformation of the double earthquakes in Turkey. Methods Using Sentinel-2 optical image data, the east-west and north-south surface coseismic deformation fields of Turkey' s double-strong earthquakes were obtained using the image correlation method, and these surface deformations were converted into sinistral strike-slip displacement along the fault direction. Results The deformation field results showed that the surface rupture lengths of the double earthquakes are approximately 280 and 130 km, respectively. The average strike-slip displacement of the first MW7.8 earthquake is 4.2±1.66 m; the maximum strike-slip displacement is 6.9±0.81 m. The average strike-slip displacement of the subsequent MW7.5 earthquake is 4.9±2.45 m, and the maximum strike-slip displacement is 9.6±1.16 m. Conclusion Comparison of the horizontal displacement results obtained using the COSI-Corr method and field measurements revealed that the maximum horizontal displacements obtained using the two methods are consistent. In contrast, the average displacement results obtained using the COSI-Corr method are slightly larger than the horizontal displacement results obtained using field measurements, attributed to the inclusion of "off-fault" deformations. Significance This study not only provides deformation data and constraints for the fault-slip inversion model but also deepens the understanding of factors controlling the rupture behavior of strike-slip faults.

Copyright of Journal of Geomechanics is the property of Journal of Geomechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study revealed that the East Anatolian Fault and all of its fault segments including the Dead Sea transform have emerged as the most vulnerable active faults for a large earthquake. The Anatolian Plate is sandwiched between Afro-Arabian and Eurasian plates characterized by the two major fault systems viz., the North Anatolian Fault system and the East Anatolian Fault system. Historical data revealed that the frequency of occurrence of large earthquakes (magnitude 7–8) in the North Anatolian Fault system is high, while the same in the East Anatolian Fault system is relatively less. However, the earthquake of February 6, 2023 in the East Anatolian Fault system did not occur as surprise rather lack of proper seismic study on the seismogenic character of the East Anatolian Fault system is to be blamed for the devastation caused by the earthquake. The last major earthquake occurred in 1872, not on the main East Anatolian Fault rather on the branch of the East Anatolian Fault system that connects Cyprus trench in the outer non-volcanic arc with the recurrence period of 150 years. It is observed that the fault segment connecting Cyprus trench was the triggering fault while the main East Anatolian Fault was activated through fault reactivations, new rupture and massive ground liquefaction occurred during 1268, 1872, and 2023 earthquakes causing massive devastations around Adana, Kahramanmaras, Gaziantep, and Antakya. Study of the paleo-earthquake records, tectonics, and geodynamics of the East Anatolian Fault revealed that the Dead Sea transform is likely to be the future triggering fault for transmitting seismogenic forces to all the surrounding active faults in the region. The East Anatolian Fault system including the Dead Sea transform has been evaluated as the fault where slow strain build-up for attaining saturation and release is going-on due to the southward propagation of arc-trench system and the subduction roll-back component of the eastern Mediterranean Sea block. Melts of the subduction roll-back slab is the source of the formation of pseudo-mantle plume and triple junction wherein Dead Sea transform is one of the tectonic elements of the triple junction for future seismogenic triggering agent. [ABSTRACT FROM AUTHOR]

Based on the amplitude spectra of surface waves, the source parameters of the strong Turkish earthquakes on February 6, 2023 (Mw = 7.8 and Mw = 7.7) were calculated in two approximations: an instantaneous point source and an elliptical shear dislocation. As a result, fault planes were identified, data were obtained on the scalar seismic moment, moment magnitude, focal mechanism, and source depth of the considered seismic events, and the integral parameters characterizing the fault geometry and its development in time were estimated. It is shown that the sources of the earthquakes under study were formed under the action of the regional stress field and their focal mechanisms were sinistral strike-slips with a strike direction close to the strike of the East Anatolian fault zone for the first event and close to the strike of the Sürgü-Çardak fault system for the second one. For the first earthquake, our estimates of the rupture duration and its length (t = 52.5 s, L = 180 km) probably refer not to the entire rupture, but only to its main phase, confined to the northeastern segments of the East Anatolian Fault and characterized by maximum displacements and values of the released seismic moment. The values of t = 30 s and L = 180 km that we obtained for the second earthquake fully characterize the entire rupture. [ABSTRACT FROM AUTHOR]

In this paper, we kinematically analyze the movements of plates and blocks of the region of southeastern Turkey, where strong earthquakes occurred on February 6, 2023, based on a homogeneous database of displacement velocities of GNSS permanent monitoring stations. Along the East Anatolian fault zone from 2008 to 2018, the Arabian Plate was established to shift relative to the Anatolian Plate, which corresponds to a left shift (without a normal component) at a rate from 1 cm/yr in the eastern part to 0.8 cm/yr in the western part. Along the Chardak fault, displacements corresponding to the left shift occurred at a rate of less than 0.7 cm/year. The revealed kinematics is confirmed by focal mechanisms and cosesismic displacements of the studied earthquakes. The M7.5 earthquake that occurred directly on the Chardak fault is not an aftershock of the M7.8 earthquake, but is a relatively independent event. An analysis of the seismic regime shows that the stresses on the East Anatolian fault after the main M7.8 event are relieved by the first large latitudinal fault zone (the Chardak fault). The results of our study suggest that the counterclockwise rotation of the Anatolian and Arabian plates associated with the opening of the Red Sea Rift is most likely decisive for the general kinematics of the plates in the region. [ABSTRACT FROM AUTHOR]

On February 6, 2023, a magnitude 7.8 earthquake and subsequent strong seismic activity struck in Kahramanmaras region, causing over 50,000 deaths in Turkey and Syria. The earthquake resulted in a surface rupture of the East Anatolian Fault Zone (EAFZ) spanning approximately 300 km. To gain new insights into the neotectonic and current stress field in the region, we compiled 141 focal mechanism solutions (FMS) of earthquakes (with magnitude M ≥ 3) that occurred along the EAFZ between 05/01/2003 and 27/02/2023. Stress inversion, by using the Win-Tensor program, indicated a predominant strike-slip tectonic regime, with few normal and thrust events related to complex fault geometry along the principal displacement zone. The calculated pressure/tension axes in the first order stress field are mainly sub-horizontal, with a maximum horizontal compressive stress (SHmax) direction of N19 ± 9.9° E, which aligns well with the slip character of the EAFZ. To reconstruct the second and third order stress fields, the study area was subdivided into five zones based on their structures and geomorphological characteristics. Reduced stress tensors were obtained for each zone, indicating a small rotation of SHmax directions under a prevailing strike-slip faulting regime. The maximum (σ1) and minimum (σ3) stress axes are nearly horizontal; while the intermediate (σ2) stress axis is nearly vertical, consistent with a predominant strike-slip regime. The results show, also, that the Kahramanmaras earthquake was caused by the neotectonic reactivation of northeast-striking sinistral strike-slip fault, with a north–south-oriented maximum horizontal stress axis. The neotectonic activity along the EAFZ aligns well with the collision models between the Arabian and Eurasian plates. Finally, a detailed seismic hazard assessment is required for the EAFZ and nearby regions. [ABSTRACT FROM AUTHOR]

The 6 February 2023, Mw 7.8 Pazarcık earthquake in the Turkey‐Syria border region raises the question of whether such a large earthquake could have been foreseen, as well as what is the maximum possible magnitude (Mmax) of earthquakes on the East Anatolian Fault (EAF) system and on continental transform faults in general. To answer such questions, knowledge of past earthquakes and of their causative faults is necessary. Here, we integrate data from historical seismology, paleoseismology, archeoseismology, and remote sensing to identify the likely source faults of fourteen Mw ≥ 7 earthquakes between 1000 CE and the present in the region. We find that the 2023 Pazarcık earthquake could have been foreseen in terms of location (the EAF) and timing (an earthquake along this fault was if anything overdue), but not magnitude. We hypothesize that the maximum earthquake magnitude for the EAF is in fact 8.2, that is, a single end‐to‐end rupture of the entire fault, and that the 2023 Pazarcık earthquake did not reach Mmax by a fortuitous combination of circumstances. We conclude that such unusually large events are hard to model in terms of recurrence intervals, and that seismic hazard assessment along continental transforms cannot be done on individual fault systems but must include neighboring systems as well, because they are not kinematically independent at any time scale. Plain Language Summary: On 6 February 2023, there was a magnitude 7.8 earthquake in the Turkey‐Syria border region. It surprised many people, including many Earth scientists, because of where it happened (on the East Anatolian fault [EAF]) and because of how large it was. People wondered whether it could have been foreseen, and how large an earthquake on this fault can really be. To figure this out, we looked at the history of earthquakes in the region in the last 1,000 years. We used information from historical seismology, paleoseismology, archeoseismology, and remote sensing to identify the faults that caused 14 earthquakes with magnitude 7 or greater in this region. We found that the location (EAF) and timing (it was due any time) of the 2023 earthquake were foreseeable, but not the magnitude. In fact, we believe that the maximum magnitude for the EAF is 8.2, and that the 2023 earthquake was below this maximum just by accident. It is hard to say how often such large events can happen, because many different things need to align. We also believe that it is necessary to look at neighboring fault systems when estimating seismic hazards, because they interact. Key Points: We identified the source faults of 14 large earthquakes along the East Anatolian and northern Dead Sea fault systemsMaximum magnitude for the East Anatolian Fault (EAF) zone is approximately 8.2Continental transforms may be described as having a collective memory [ABSTRACT FROM AUTHOR]

We derive the ALOS‐2 coseismic interferograms, pixel‐offsets and Sentinel‐2 sub‐pixel offsets of the 2023 Mw7.8 and Mw7.7 Kahramanmaras, Turkey earthquake sequence. Offset maps show that the sequence ruptured ∼300 km along the East Anatolian Fault (EAF) and ∼180 km along the secondary Cardak and Dogansehir faults. We infer the coseismic slip distribution and interseismic fault motion by inverting the co‐ and inter‐seismic observations. Inversion results show that the coseismic slip (∼8.0 m) and interseismic strike‐slip rate (∼4.6 mm/yr) on the main rupture of the Mw7.8 event are basically consistent with the ∼8.4 m and ∼3.9 mm/yr of the Mw7.7 event. Most coseismic slips of the Mw7.8 and Mw7.7 events occur within 10 and 12 km at depth, respectively, in keeping with the interseismic locking depth of 10.4 ± 3.3 km and 11.1 ± 3.1 km. This implies that the coseismic rupture kinematics correlate with the interseismic strain accumulation. Moreover, static stress changes show that the Mw7.7 event is likely promoted by ∼2 bar stress increase from the Mw7.8 event on the central section of its main rupture. Plain Language Summary: The middle and northern sections of the East Anatolian Fault (EAF) have experienced seven major earthquakes (M > 6.0) since the twentieth century, in accordance with the fast slip rate (∼10.5 mm/yr) and shallow locking depth (∼5 km) (Bletery et al., 2020, https://doi.org/10.1029/2020gl087775), leaving a well‐known seismic gap, the Pazarcık segment in the southern section of the EAF. Stress analysis by Nalbant et al. (2002, https://doi.org/10.1016/s0012-821x(01)00592-1) suggested that this seismic gap has potential to produce an Mw ≥ 7.3 earthquake. The 2023 Mw7.8 and Mw7.7 Kahramanmaras, Turkey earthquake sequence ruptured the Pazarcık segment. This earthquake sequence offers a valuable opportunity to explore the critical stage of the seismic cycle from interseismic strain accumulation to coseismic rupture. We extract the surface fault traces from the deformation maps derived from the ALOS‐2 interferometric synthetic aperture radar (InSAR), pixel offset and Sentinel‐2 sub‐pixel offset measurements, and then construct a seven‐segment fault geometric model according to the fault segmentation based on Duman and Emre (2013, https://doi.org/10.1144/SP372.14). By inverting the coseismic interferograms and pixel offsets and the interseismic LOS velocities from Weiss et al. (2020, https://doi.org/10.1029/2020GL087376), we determine the coseismic slip model of Mw7.8 and Mw7.7 earthquakes, and relate it to the interseismic kinematics. Key Points: We drive a complete series of coseismic deformation maps and detailed slip distribution of the 2023 Kahramanmaras earthquakesThe Mw7.7 event produced normal dip‐slip (∼6 m) near the Goksun releasing bend and thrust dip‐slip (∼2 m) on the Dogansehir faultThe coseismic slip behaviors on the Cardak and Pazarcık faults correlate with the interseismic kinematics [ABSTRACT FROM AUTHOR]

The East Anatolian Fault in southern Turkey ruptured on 6 February 2023, causing a Mw 7.8 earthquake (EQ1), one of the largest strike‐slip events recorded on land. ∼9 hr later, earthquake of Mw 7.7 (EQ2) occurred to the north of EQ1. We investigate here near‐field coseismic ionospheric perturbations (CIP) caused by acoustic waves (AWs) excited by coseismic vertical crustal movements. We find that observed CIP periods were somewhat longer for EQ1 than EQ2. EQ1 also showed azimuthal dependence in CIP amplitudes that cannot be explained by known factors such as geomagnetism and line‐of‐sight geometry. Numerical experiments revealed that CIP by EQ1 can be well reproduced by assuming a suite of sources along the fault that successively ruptured. Small but significant dependence of amplitudes and periods on azimuths were caused by interference of AWs from multiple sources. We also found that CIP amplitudes of strike‐slip earthquakes tend to be lower than dip‐slip earthquakes. Plain Language Summary: Fault dislocations in earthquakes cause vertical movement of the surface and excite acoustic waves (AWs) in the overlying atmosphere which propagate upward with increasing amplitudes. Such waves reach the ionosphere and disturb electron density distribution there, causing disturbances in numbers of electrons along the line‐of‐sights connecting ground GNSS receivers and satellites. So far, such near‐field co‐seismic ionospheric perturbations are modeled by assuming single acoustic pulse from the surface, although large earthquakes often involve ruptures of multiple fault segments spanning hundreds of kilometers. Here we demonstrate that interference of AWs from these multiple sources makes differences in the perturbations amplitudes and periods at GNSS stations in different azimuths from the epicenter. Key Points: Mw 7.8 and Mw 7.7 February 2023 Turkey earthquakes produced typical ionospheric perturbationsFor the first earthquake, we found small but significant difference in the perturbation amplitudes that cannot be explained by known factorsBy assuming multiple sources along the fault and interference of acoustic waves from them, we can explain the observed azimuthal asymmetry [ABSTRACT FROM AUTHOR]

The East Anatolian Fault Zone (EAFZ) is a left-lateral transform fault zone located between the Anatolian and Arabian plates. In this study, in order to image the upper crustal structure beneath the eastern segments of EAFZ, 3D seismic velocity variations are computed using local earthquake tomography. The initial catalog for the tomography process consists of 2200 well-located earthquakes recorded at 49 seismic stations around the study region between 2007 and 2020. 1D initial velocity model is constructed based on previous studies in the region. The maximum number of iterations and the velocity perturbations which sustain the linearity of the inversion are determined based on the detailed tests. Reliable zones of the final model are decided based on the Derivative Weighted Sum and Hit Count distribution. The resulting velocity model displays a clear velocity contrast across the surface trace of the EAFZ down to a depth of 12 km. While the Anatolian side of the fault displays higher velocities associated with the ophiolitic units in the region, the south of the fault zone is represented by lower velocities due to sedimentary deposits. The vertical cross-sections of tomographic models show a north dipping fault between Palu and Çelikhan. The complete earthquake catalog is relocated using the 3D velocity model. Together with the obtained velocity model, the relocated hypocenters indicate that the dip of the EAFZ is not uniform, the Palu segment dips to the north with an angle of ~80°, while the Pütürge and Erkenek segments dip to the north with a lower angle of ~60-70°. [ABSTRACT FROM AUTHOR]

This study re-evaluates the ∼20 Myr development of the Dead Sea Fault System (DSFS) and its tectonic definition as a transform plate boundary. The DSFS conveys sinistral displacement between the Arabian-Sinai plates: ∼105 km along its ∼400 km-long southern segment (Gulf of Aqaba-Eilat to the Hula basin); ∼90 km and 4–16 km along the central and northern segments (∼190 km long each, across Lebanon, western Syria, and southern Turkey). A review of previous studies, combined with new seismological data analysis, associates the northward displacement decline with obstacles along the DSFS propagation path. During the Miocene, DSFS propagated up to the NW-trending Irbid rift (1st obstacle) and splayed NW towards the Mediterranean and NE along the Late Cretaceous Palmyra fold-thrust belt (2nd obstacle). Its reactivation uplifted the Hermon and the Anti-Lebanon mountain ranges. Northward DSFS propagation into the cold and rigid Aleppo plateau lithosphere (3rd obstacle) was stalled until the early Pliocene (∼5 Ma), when volcanism and ongoing regional tectonic forcing enabled the DSFS to shift to the Yammouneh fault and rupture through the Missyaf-Ghab branch farther north (central and northern segments, respectively). During the Pleistocene-recent, connection of the DSFS with the ophiolite belt and East Anatolian Fault System (EAFS) along the Bitlis suture zone (4th obstacle) has not yet been established. Seismological data show a clear separation between the EAFS and the DSFS, while seismicity is scattered across the Aleppo plateau and the central and northern DSFS segments. In contrast, seismicity is localized along the southern DSFS segment. Our findings suggest that, at present, the DSFS has still not made a structural, seismologic, and tectonic connection with the EAFS. Hence, we redefine the DSFS as a pre-transform and suggest its interaction with the EAFS is a world-class example of a fault-fault-fault triple junction in the making. • The study re-evaluates ∼20 Myr tectonic development of the Dead Sea Fault System (DSFS). • DSFS crossed four rheologic obstacles that stalled and diverted its propagation. • DSFS displacement decreases northwards from ∼105 to 90 and 16 km. • The DSFS is not connected tectonically or seismically to the East Anatolian Fault System (EAFS). • We redefine DSFS as a pre-transform. [ABSTRACT FROM AUTHOR]

The East Anatolian Fault (EAF) is an active left-lateral strike-slip fault extending between Karlıova (Bingöl) in the northeast and Iskenderun Bay in the southwest. The Palu, which is the subject of the study area, is located on the Palu segment of the EAF. The Palu segment starts from the northeast of Palu, and is approximately 77 km long, and reaches the Lake Hazar after passing the Baltaşı Plain. Maximum shaking intensity in the earthquake listed in historical catalogs is estimated to have been Mercalli Intensity VIII, with conflicting accounts of as few as 8.000-10.000 to as many as 50.000 people killed. An examination of contemporary documents, books and administrative archives in the State Archives Head of Presidency Republic of Turkey for the district reveal that the extent of damage and the number of fatalities in the earthquake have been considerably inflated by these historical catalogs.

Copyright of Geomatik is the property of Murat Yakar and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

While the structural deformation at the Arabia-Anatolia-Africa junction is critical for understanding eastern Mediterranean tectonics, it remains debatable (extensional or compressional). Field survey of the 2023 Mw7.7 Pazarcik earthquake surface rupture along the Amanos Range, and microstructure and composition analyses of related fault rock were performed to investigate this issue. The surface rupture shows transtensional branches, with the main and secondary strands displaying sinistral (normal) offsets of 2.0–4.0 (0.4–0.9) and 1.0 (0.2) m. Slip plane of the secondary fault is marked by a ∼20 cm wide extensional fracture dividing fault breccia from gouge. Meanwhile, the gouge (26 % calcite, 38% serpentine and 36% smectite) is also dominated by tension cracks microscopically. In contrast to the widespread extensional deformation, geological evidence imply that this fault had experienced reverse slip in the Quaternary, as shown by thrusting of serpentine onto alluvium and the consistency of R foliations with reverse shear. We interpret it as the SW continuation of the East Anatolia fault (EAF) that was formerly characterized by transpressional deformation, and reactivated transtensionally due to the change of fault strike during this earthquake. In the broader Mediterranean tectonics framework, the Amanos segment might be interpreted as a recently formed component linking the Karasu fault to the EAF. • The coseismic rupture along the Amanos Range is overall transtensional. • The largest branch fault reactivated was previously transpressional. • This transformation happened in the Quaternary. • It highlights the tectonic evolution in the Arabia-Anatolia-Africa junction zone. [ABSTRACT FROM AUTHOR]

On 24 January 2020, a devastating earthquake struck the town of Sivrice in Elazığ province at 20:55 local time (17:55 UTC), resulting in 41 death and significant loss of property. The magnitude of the earthquake was determined to be Mw 6.8 and strong shaking of main shock lasted about 20 seconds. The Sivrice earthquake triggered about 30 landslides over an area of ~55 km². This article presents the preliminary results of comprehensive study on mapping of the distribution of landslides, lateral spreading and other ground damaged effects triggered by the Sivrice earthquake occurred on the East Anatolian Fault. Following Sivrice earthquake, based on detailed on-ground field studies: (1) The Sivrice earthquake produced fewer landslides than empirical prediction for shallow earthquakes of these magnitudes (Mw 6.8) would suggest; (2) the Sivrice earthquake triggered extensive lateral spreading in Holocene age river banks, and result in the ground tears, opening surface cracks and fissure on flat ground; (3) primary surface rupture was not produced by Sivrice earthquake. [ABSTRACT FROM AUTHOR]

The co-seismic, and post-seismic effects of 18 earthquakes that occurred since 1822 were modelled in conjunction with a regionally variable secular inter-seismic effect in order to investigate how the Coulomb stress field in the eastern part of the North Anatolian and the East Anatolian Fault Zones, have evolved over the past two centuries. Results show that viscoelastic post-seismic relaxations caused by the 1939 Ms 7.9 Erzincan earthquake is still strong and influencing the seismic activity in the region. Post-seismic effects have increased the stress on the Yedisu segment as much as 5.3 bars, whereas supressed stress on the Kahramanmaras-Malatya segment. In general, increases in stress due to viscous-elastic effects are comparable, or in certain cases even larger than the increases in stress caused by co-seismic deformations. This indicates that the additional stress changes derived from viscoelastic deformations could be significant and should be taken into consideration when assessing seismic hazard along the active seismic zones. Two regions are identified as having high positive Coulomb stress changes therefore high seismic hazard; a segment close to Bingol Province in the East Anatolian Fault Zone and the Yedisu segment of the North Anatolian Fault Zone. [ABSTRACT FROM AUTHOR]

The East Anatolian Fault (EAF) is a morphologically distinct and seismically active left-lateral strike-slip fault that extends for ~400 km and forms the Arabian/Anatolian plate boundary in southeastern Turkey. The EAF together with its conjugate fault, the North Anatolian Fault, help accommodate the westward escape of the Anatolian plate from the Arabian/Eurasian collision zone. Morphotectonic features along the EAF provide insights into the nature of landscape development and aid in understanding variations in tectonic activity and fault evolution. Several geomorphic indices, namely stream length-gradient index, mountain-front sinuosity, valley width to valley height ratio, basin asymmetry factor, and drainage density, and hypsometric analysis were examined using digital elevation models. The EAF can be divided into five segments based on its tectonic geomorphology. The stream length-gradient index values are between 50 and 350 along the five segments. Mountain-front sinuosity varies from 1.01 to 1.46 on the five segments. The mean ratio of valley floor width to valley height along the studied segments ranges from 0.11 to 1.32, which is well correlated with the mountain-front sinuosity values. Basin asymmetry factors for 18 catchments range from 1.88 to 26.25 along the study fault zone. Drainage density values for the studied catchments range from 3.5 to 5.6. Finally, the hypsometric analysis index of the 18 catchments indicates high, intermediate, and low relative tectonic activity. The results show that all geomorphic indices are remarkably uniform along the entire length of the fault, thus indicating that fault development was essentially coeval along its length, which supports the view that the present-day Arabian/Anatolian plate boundary (delimited by the EAF) jumped eastwards from the Malatya-Ovacık Fault at ~3 Ma. This is in good agreement with the nearly uniform geological offsets and the GPS-determined present-day slip rate of ~10 mm/year along the entire fault. [ABSTRACT FROM AUTHOR]

The series of earthquakes that took place on February 6, 2023 caused one of the saddest major calamities in Türkiye. The first major earthquake of magnitude Mw7.7 broke the Pazarcık and Erkenek segments moving north on the East Anatolian Fault Zone (EAFZ) between Türkoğlu and Çelikhan. According to the Coulomb failure criterion, the Pazarcık earthquake (Mw7.7) increased stress on the Sürgü-Çardak Fault, a segment on the north splay of the EAFZ, and nine hours later the Elbistan earthquake (Mw7.6) occurred. This great event ruptured the Çardak Fault, the western part of the E -W trending Sürgü-Çardak Fault between Nurhak and Göksun. The Amanos Fault, which extends from Türkoğlu south to Antakya, broke almost simultaneously to the first Pazarcık earthquake. Similarly, the earthquake that broke the Amanos Fault transferred increased stress to its south-western neighbour, the Cyprus-Antakya Transform Fault, triggering the 6.3 magnitude Samandağ earthquake 14 days later. The February 2023 earthquakes, which caused the collapse of >100,000 buildings and the death of >50,000 people, created surface ruptures hundreds of kilometres in length and caused different displacements on different faults, the two largest of which were 4.6 and 6.7 m. On all the faults where the deadly earthquakes occurred in February 2023, inversion of the focal mechanisms of the earthquakes (main shocks and their aftershocks) indicates a transtensional stress regime, or a change from strike-slip to normal slip. For all strike-slip inversions, the R values are <0.45 indicating transtension. The stress tensors obtained indicate left-lateral movement with normal component on all faults where the earthquakes occurred. The transtensional regime, which is thought to reflect regional tectonics, is the result of forces caused by relative movements of Arabia, eastern Mediterranean and Eurasia. • Earthquakes in February 2023 caused surface ruptures along four different faults. • Every earthquake in February 2023 has a left lateral strike-slip character with a normal component. • The forces brought about by the relative motion of Arabia, Africa and Anatolia resulted in the transtensional stress regime. [ABSTRACT FROM AUTHOR]

Deltas contain sedimentary records that are not only indicative of water-level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures. The Kürk lacustrine delta lies at the south-western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re-evaluates water-level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic-reflection profiles and side-scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water-level changes provides a temporal framework for the depositional record. In addition to the common soft-sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake-induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X-ray imagery, X-ray diffraction, loss-on-ignition, grain-size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post-seismic sediment reworking of earthquake-triggered landslides. [ABSTRACT FROM AUTHOR]

The North Anatolian Fault is a 1200 km long strike-slip fault system connecting the East Anatolian convergent area with the Hellenic subduction zone and, as such, represents an intracontinental transform fault. It began forming some 13-11 Ma ago within a keirogen, called the North Anatolian Shear Zone, which becomes wider from east to west. Its width is maximum at the latitude of the Sea of Marmara, where it is 100 km. The Marmara Basin is unique in containing part of an active strike-slip fault system in a submarine environment in which there has been active sedimentation in a Paratethyan context where stratigraphic resolution is higher than elsewhere in the Mediterranean. It is also surrounded by a long-civilised rim where historical records reach well into the second half of the first millennium BCE (before common era). In this study, we have used 210 multichannel seismic reflexion profiles, adding up to 6210 km profile length and high-resolution bathymetry and chirp profiles reported in the literature to map all the faults that are younger than the Oligocene. Within these faults, we have distinguished those that cut the surface and those that do not. Among the ones that do not cut the surface, we have further created a timetable of fault generation based on seismic sequence recognition. The results are surprising in that faults of all orientations contain subsets that are active and others that are inactive. This suggests that as the shear zone evolves, faults of all orientations become activated and deactivated in a manner that now seems almost haphazard, but a tendency is noticed to confine the overall movement to a zone that becomes narrower with time since the inception of the shear zone, i.e., the whole keirogen, at its full width. In basins, basin margins move outward with time, whereas highs maintain their faults free of sediment cover, making their dating difficult, but small perched basins on top of them in places make relative dating possible. In addition, these basins permit comparison of geological history of the highs with those of the neighbouring basins. The two westerly deeps within the Sea of Marmara seem inherited structures from the earlier Rhodope-Pontide fragment/Sakarya continent collision, but were much accentuated by the rise of the intervening highs during the shear evolution. When it is assumed that below 10 km depth the faults that now constitute the Marmara fault family might have widths approaching 4 km, the resulting picture resembles a large version of an amphibolite-grade shear zone fabric, an inference in agreement with the scale-independent structure of shear zones. We think that the North Anatolian Fault at depth has such a fabric not only on a meso, but also on a macro scale. Detection of such broad, vertical shear zones in Precambrian terrains may be one way to get a handle on relative plate motion directions during those remote times. La faille nord-anatolienne est constituee d'un systeme de failles decrochantes d'une longueur de 1200 km qui relie le secteur convergent anatolien a la zone de subduction hellenique elle represente ainsi, une faille transformante intracontinentale. Elle a commence a se former il y a environ 13 a 11 Ma dans une ceinture deformee dominee par des deplacements de decrochement (<< keirogene >>), nomme la zone de cisaillement nord-anatolienne; elle s'elargit d'est en ouest. Elle atteint sa largeur maximale de 100 km a la latitude de la mer de Marmara. Le bassin de Marmara est unique en ce qu'il contient une partie d'un systeme actif de failles de decrochement dans un environnement sous-marin ou ilya eu de la sedimentation active dans un contexte de mer Paratethys et ou la resolution stratigraphique est plus elevee qu'ailleurs en Mediterranee. La faille est aussi entouree par une bordure ou, grace aux civilisations de longue date, il existe des documents historiques datant de la deuxieme moitie du premier millenaire avant notre ere. Dans la presente etude, nous avons utilise les donnees obtenues par 210 profils de reflexion sismique multicanale, ce qui donne un total de 6210 km de profils; nous avons aussi utilise de la bathymetrie a haute resolution et des profils de fluctuation de longueur d'onde disponibles dans la litterature pour cartographier toutes les failles plus recentes que l'Oligocene. Pour ces failles, nous distinguons celles qui recoupent la surface et celles qui ne la recoupent pas. Pour ces dernieres, nous avons cree un tableau temporel de generation de failles basee sur la reconnaissance de la sequence sismique. Les resultats sont surprenants; en effet, peu importe l'orientation des failles, elles contiennent toutes des sousensembles actifs et des sous-ensembles non actifs. Cela suggere qu'a mesure de revolution de la zone de cisaillement, les failles de toutes directions sont activees et desactivees d'une maniere qui semble presque aleatoire. Cependant, nous notons une tendance a restreindre le mouvement general a une zone qui se retrecit avec le temps depuis de debut de la zone de cisaillement, c.-a-d. tout le<>, a sa pleine largeur. Dans les bassins, avec le temps, les bordures se deplacent vers l'exterieur alors que les zones surelevees gardent leurs failles libres de couverture sedimentaire, ce qui complique la datation. Toutefois, de petits bassins a leur sommet permettent d'obtenir une datation relative. De plus, ces bassins permettent de comparer l'histoire geologique des zones surelevees a celle des bassins avoisinants. Deux creux, situes a l'ouest dans la mer de Marmara, semblent etre des structures heritees de la collision entre le fragment Rhodope-Pontide et le continent Sakarya. Cependant, ils ont ete grandement accentues par le soulevement des zones surelevees durant Devolution du cisaillement. Lorsque nous partons de l'hypothese qu'a une profondeur superieure a 10 km, les failles qui forment actuellement la famille de failles de Marmara pourraient avoir des largeurs approchant les 4 km, l'image qui en ressort ressemble a une version agrandie d'une fabrique de zone de failles au facies des amphibolites. Cette inference concorde avec une structure de zones de cisaillement, independante de l'echelle. Nous croyons que la faille nord-anatolienne constitue un systeme qui a une telle fabrique en profondeur, non seulement a echelle moyenne mais aussi a grande echelle. La detection de telles larges zones verticales de cisaillement dans des terrains precambriens pourrait etre une maniere de comprendre les directions relatives des plaques a ces temps anciens. [Traduction par la Redaction], In pietate memoriam J. Tuzo Wilson Introduction In 1965, J. Tuzo Wilson defined a new kind of fault that could not be accounted for by Anderson's theory of faulting in [...]

We investigate the postseismic viscoelastic flow in the lower crust and upper mantle due to the 19th and 20th century large earthquakes in eastern Turkey. Three possible rheological models are used in the viscoelastic postseismic deformation analysis to assess the extent to which these events influence the velocity fields at GPS sites in the region. Our models show that the postseismic signal currently contributes to the observed deformation in the eastern part of the North Anatolian fault and northern and middle parts of the East Anatolian Fault Zone, primarily due to the long-lasting effect of the M s 7.9 1939 earthquake. None of the postseismic displacement generated by the M s 7.5 1822 earthquake, which is the earliest and the second largest event in the calculations, exceeds observed error range at the GPS stations. Our results demonstrate that a postseismic signal can be identified in the region and could contribute up to 3–25% of the observed GPS measurements. [ABSTRACT FROM AUTHOR]

The East Anatolian Fault System (EAFS) is the second major fault system in Turkey, following the North Anatolian Fault System (NAFS). Unlike the NAFS, which produced 11 large earthquakes in the last ∼75 years, the EAFS has been relatively quiet during the same period of time. While historical records show that the EAFS has the potential to produce large earthquakes, the fault slip rates on the EAFS were not studied in detail, and were not quantified sufficiently. This is possibly due to the relatively low seismicity and slow slip-rates of the EAFS with respect to the NAFS. However, the determination of the slip rates of the EAFS is equally important in order to understand the kinematics of the Anatolian plate. In this study, we collected and analyzed new survey-type GPS data, and homogeneously combined published velocities from other studies, to form the most complete GPS data set covering the EAFS. In particular, continuous GPS observations were utilized for the first time to study the northern part of the EAFS. The results of the analysis give well-constrained slip rates of the northwestern segments of the EAFS, which is further connected to the Dead Sea Fault System (DSFS) in the south. The results show that while the slip rate of the EAFS is nearly constant (∼10 mm/yr) to the north of Türkoğlu, it then decreases to 4.5 mm/yr in the south. The slip rate on the northern part of the Dead Sea Fault System (DSFS) was also found to be 4.2 ± 1.3 mm/yr, consistent with earlier studies. The contraction rates along the EAFS are below 5 mm/yr, except for the northernmost part near Karliova, where it reaches a maximum value of 6.3 ± 1.0 mm/yr. The results also show that two well-known seismic gaps across the EAFS, Palu-Sincik and Çelikhan-Türkoğlu segments, have slip deficits of 1.5 m and 5.2 m and have the potential to produce earthquakes with magnitudes of M w 7.4 and M w 7.7, respectively. [ABSTRACT FROM AUTHOR]

İnceleme alanı, Elazığ ilinin yaklaşık 30 km güneydoğusundaki Hazar Gölü'nün doğu kesimlerinde yer alan yaklaşık 95 km 2 lik bir alanı kapsar. Araştırılan sahada yaşları Jura'dan Orta Eosen'e kadar değişen magmatik, sedimanter ve volkanosedimanter birimler yüzeylerler. İnceleme alanının temelini Üst Jura-Alt Kretase yaşlı Guleman Ofiyoliti oluşturur. Bunların üzerinde açılı uyumsuz olarak duran, Maastrihtiyen-Alt Eosen yaşlı Hazar Grubu alttan üste doğru; kırmızı çakıltaşlarıyla temsil olunan Ceffan formasyonu, fliş özelliğindeki Simaki formasyonu ve kireçtaşlarından oluşan Gehroz formasyonu olmak üzere üç formasyondan meydana gelir. İnceleme alanının kuzeyinde, Guleman Ofiyoliti üzerinde uyumsuz olarak duran bir diğer birim de Orta Eosen yaşlı Maden Karmaşığıdır. Andezitik-bazaltik volkanitlerin eşlik ettiği volkanosedimenter birim, tabanda çakıltaşı ve kumtaşlarıyla başlayıp üste doğru çamurtaşı-marn ve kireçtaşlarına geçer. Guleman ofiyoliti, üstündeki Hazar Grubu'nu oluşturan birimlerle birlikte kuzeyden güneye doğru, Maden Karmaşığı üzerine Orta Eosen sonrasında naplar şeklinde itilmişlerdir. Çalışma alanının içinden geçen doğrultu atımlı sol yönlü Doğu Anadolu Fayı, burada yaklaşık 5-6 km genişliğinde bir zon şeklindedir. KD-GB doğrultulu (K60°D), yüksek eğim atım bileşenli, birbirine yaklaşık paralel birkaç büyük faydan oluşur.

We present a new strain-rate and associated kinematic model for the eastern and central parts of Turkey. In the east, a quasi N-S compressional tectonic regime dominates the deformation field and is partitioned through the two major structural elements of the region, which are the conjugate dextral strike-slip North Anatolian Fault Zone (NAFZ) and the sinistral strike slip East Anatolian Fault Zone (EAFZ). The observed surface deformation is similar to that inferred by anisotropy studies which sampled the region of the mantle closer to the crust (i.e. the lithospheric mantle and the Moho), and is dependent on the presence or absence of a lithospheric mantle, and of the level of coupling between it and the overlaying crust. The areas of the central and eastern parts of Turkey which are deforming at elevated rates are situated above areas with strong gradients in crustal thickness. This seems to indicate that these transition zones, situated between thinner and thicker crusts, promote more deformation at the surface. The regions that reveal elevated strain-rate values are 1) the Elaziğ–Bingol segment of the EAFZ, 2) the region around the Karlıova triple-junction including the Yedisu segment and the Varto fault, 3) the section of the NAFZ that extends from the Erzincan province up to the NAFZ-Ezinepazarı fault junction, and 4) sections of the Tuz Gölü Fault Zone. Other regions like the Adana basin, a significant part of the Central Anatolian Fault Zone (CAFZ), the Aksaray and the Ankara provinces, are deforming at smaller but still considerable rates and therefore should be considered as areas well capable of producing damaging earthquakes (between M 6 and 7). This study also reveals that the central part of Turkey is moving at a faster rate towards the west than the eastern part Turkey, and that the wedge region between the NAFZ and the EAFZ accounts for the majority of the counter clockwise rotation between the eastern and the central parts of Turkey. This change in movement rate and direction could be the cause of the extensional deformation and respective crustal thinning, with the resulting upwelling of warmer upper mantle observed in tomographic studies for the region between the Iskenderun bay and the CAFZ. The partitioning of deformation into an extensional regime could be the cause of the relatively low levels of strain-rate in the south-west part of the EAFZ and the northern part of the Dead Sea Fault Zone. Finally, using this new compilation of GPS data for the central-eastern part of Turkey, we obtained a new Anatolia–Eurasia rotation pole situated at 2.01°W and 31.94°N with a rotation rate of 1.053 ± 0.015 ° / Ma . [ABSTRACT FROM AUTHOR]

Magnetotelluric (MT) studies can map subsurface resistivity structure and have located zones of low resistivity (high conductivity) within major strike-slip fault zones worldwide which have been interpreted as regions of elevated fluid content. This study describes MT data from the eastern part of the North Anatolian and the East Anatolian Fault Systems (NAFS and EAFS) and presents the results of the first MT studies of these faults. The inversion of the MT data produced 2-D resistivity models which showed that both fault systems are underlain by a broad low resistivity zone that extended into the lower crust. However, the resistivity beneath the East Anatolian Fault System was much lower than beneath the eastern part of the North Anatolian Fault System. These conductors begin at a depth of 10 km – not at the surface as on the central San Andreas Fault (SAFS). This difference is interpreted as being due to the fact that the EAFS and NAFS are young fault systems characterized in the upper crust by multiple fault traces – as opposed to the SAFS that has evolved into a single through going fault. Different stages of the seismic cycle may also influence the resistivity structure, although this is difficult to constrain without knowledge of time variations in resistivity structure at each location. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the earthquake hazard of the East Anatolian Fault Zone by determining the a and b parameters in a Gutenberg-Richter magnitude-frequency relationship. For this purpose, the East Anatolian Fault Zone is divided into five different source zones based on their tectonic and seismotectonic regimes. We calculated the b value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship, from the maximum likelihood method (ML). Also, we estimated the mean return periods, the most probable maximum magnitude in the time period of t years and the probability for an earthquake occurrence for an earthquake magnitude ≥ M during a time span of t years. We then produced a and b value maps using the ML. We obtained the lowest b value in Region 1 covered Karlıova triple junction. This conclusion is strongly supported from the probability value, which shows the largest value (90 %) for an earthquake with magnitude greater than or equal to 6.0. The mean return period for such a magnitude is the lowest in this region (43 years). The most probable magnitude in the next 100 years was calculated, and we determined the highest value around Karlıova triple junction. According to these parameters, Region 1 covered the Karlıova triple junction and is the most dangerous area around the East Anatolian Fault Zone. [ABSTRACT FROM AUTHOR]

Structural data and a regional tectonic interpretation are given for the NE-SW-trending Hatay Graben, southern Turkey, within the collision zone of the African (Arabian) and Eurasian (Anatolian) plates. Regional GPS and seismicity data are used to shed light on the recent tectonic development of the Hatay Graben. Faults within Upper Cretaceous to Quaternary sediments are categorized as of first-, second- and third-order type, depending on their scale, location and character. Normal, oblique and strike-slip faults predominate throughout the area. The flanks of the graben are dominated by normal faults, mainly striking parallel to the graben, that is, 045-225°. In contrast, the graben axis exhibits strike-slip faults, trending 100-200°, together with normal faults striking 040-060° and 150-190° (a subset strikes 110-130°). Similarly orientated normal faults occur throughout Upper Cretaceous to Pliocene sediments, whereas strike-slip faults are mostly within Pliocene sediments near the graben axis. Stress inversion of slickenline data from mostly Pliocene sediments at ten suitable locations (all near the graben axis) show that σ[sub3] directions (minimum stress axis extension direction) are uniform in the northeast of the graben but orientated at a high angle to the graben margins. More variable σ[sub3] directions in the southwest may reflect local block rotations. During Miocene times, the Arabian and Anatolian plates collided, forming a foreland basin associated with flexurally controlled normal faulting. During the Late Miocene there was a transition from extension to transtension (oblique extension). The neotectonic Hatay Graben formed during the Plio-Quaternary in a transtensional setting. In the light of modern and ancient comparisons, it is suggested that contemporaneous strain was compartmentalized into large-scale normal faults on the graben margins and mainly small-scale strike-slip faults near the graben axis. Overall, the graben reflects Plio-Quaternary westward tectonic escape from a collision zone towards the east to a pre- or syn-collisional zone to the west in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

The East Anatolian Fault Zone (EAFZ) is among the most important active continental transform fault zones in the world as testified by major historical and minor instrumental seismicity. The first paleoseismological exploratory trenching study on the EAFZ was done on the Palu–Lake Hazar segment (PLHS), which is one of the six segments forming the fault zone, in order to determine its past activity and to assess its earthquake hazard.The results of trenching indicate that the latest surface rupturing earthquakes on this segment may be the Ms=7.1+ 1874 and Ms=6.7 1875 events, and there were other destructive earthquakes prior to these events. The recurrence interval for a surface rupturing large (M>7) earthquake is estimated as minimum 100±35 and maximum 360 years. Estimates for the maximum possible paleoearthquake magnitude are (Mw) 7.1–7.7 for the Palu–Lake Hazar segment based on empirical magnitude fault rupture relations.An alluvial fan dated 14,475–15,255 cal years BP as well as another similar age fan with an abandoned stream channel on it are offset in a left-lateral sense 175 and 160.5 m, respectively, indicating an average slip rate of 11 mm/year. Because 127 years have elapsed since the last surface rupturing event, this slip rate suggests that 1.4 m of left-lateral strain has accumulated along the segment, ignoring possible creep effects, folding and other inelastic deformation. A 2.5 Ma age for the start of left-lateral movement on the segment, and in turn the EAFZ, is consistent with a slip rate of 11 mm/year and a previously reported 27 km total left-lateral offset. The cumulative 5–6 mm/year vertical slip rate near Lake Hazar suggests a possible age of 148–178 ka for the lake. Our trenching results indicate also that a significant fraction of the slip across the EAFZ zone is likely to be accommodated seismically. The present seismic quiescence compared with the past activity (paleoseismic and historic) indicate that the EAFZ may be “locked” and accumulating elastic strain energy but could move in the near future. [Copyright &y& Elsevier]

Unlike the North Anatolian fault zone, which has produced 11 large earthquakes since 1939, the East Anatolian fault zone (EAFZ) has been relatively quiescent in the last century when compared to historical records and has therefore accumulated significant stresses along its length. Determination of the location and likely magnitude of a future probable earthquake along the EAFZ is of interest both because of this history of large earthquakes, (M&ap;8), and the density of population in the area. Here we calculate stress evolution along the fault zone due to both seismic and tectonic loading since 1822. A sequence of 10 well constrained historical earthquakes is selected and the resulting stresses are calculated, summed with tectonic loading stresses and resolved onto the mapped active faults. We identify two areas of particular seismic risk, one of which might be expected to yield a large event. Our results are sensitive to the previous history of large earthquakes in the region and indicate a need for detailed investigations to constrain the exact rupture geometries of previous earthquakes on these segments. [Copyright &y& Elsevier]

Turkey is located on active fault zones such as the East Anatolian Fault (EAF), the North Anatolian Fault (NAF) and the Anatolian-Aegean Subduction Zone (AASZ). Ground seismicity activities of the NAF zone are relatively active compared with other faults. Eleven high-intensity earthquakes have been produced on this fault zone since 1939. Whereas the EAF zone was relatively quiescent in the last century, on the basis of historical records, destructive seismic activities occurred on the EAF zone in the last two decades. In this study, the rupture reason of faults, updated active fault data, and seismic maps are presented briefly. Moreover, failure reasons and failure mechanism of conventional masonry structures damaged from seismic ground motions on the EAF zone are evaluated in detail. Possible solutions are suggested on the basis of seismic codes. For this purpose, EAF-sourced earthquakes, i.e. 2003 Bingöl, 2010 Kovancılar (Elazığ), 2011 Maden (Elazığ), 2011 Tabanlı (Van) and Edremit (Van) hit in last two decades on this fault are investigated. Failures of conventional masonry buildings triggered from these earthquakes are assessed. Statistical evaluation, damage of earthquakes and failure pattern are deeply investigated and revealed. Eventually, one of the most significant reasons of severe damage or collapse to masonry structures due to this seismicity is the inability to construct the structures according to the requirements of seismic codes. • East Anatolian earthquakes and damages to masonry dwellings were presented. • Acceleration response spectra were evaluated for ξ=0, 2, 5, 7 and 10% of damping. • Past and Present Seismological Activity of East Anatolian Fault zone. • Damage of masonry dwelling, lessons & learned were presented. [ABSTRACT FROM AUTHOR]

On February 21, 2007, a moderate-sized (Mw 5.7) earthquake struck the town of Sivrice (Elazig, Turkey) located within the East Anatolian Fault (EAF) zone that forms the boundary between the Arabian and Anatolian plates. The earthquake source parameters of the mainshock reported by different agencies are significantly different. In the mean time, the relation of this earthquake to the EAF has not been fully explored. In this study, we combine remotely sensed Synthetic Aperture Radar data obtained from ENVISAT ASAR images (European Space Agency) with relocated seismicity to map the observed surface displacement field, resolve the earthquake source parameters and determine the fault plane geometry. We calculated coseismic interferograms from both ascending and descending orbits and modeled them by elastic dislocations on rectangular fault surfaces using a downhill simplex simulated annealing algorithm. InSAR analysis and seismicity distribution reveal that the earthquake took place on the Adıyaman fault (AF), a major southern splay of the EAF. The ruptured part of the AF has a listric geometry with an oblique normal slip (rake − 73 ± 21 °), and a strike of N42 ° E. The computed coseismic slip is 64 ± 18 cm with a moment magnitude of Mw 5.9. The resolved fault plane has a steep dip (greater than 80 °) near the surface and mildly dipping at depths between 3.6 and 8.5 km (dip 63 ± 4 °). The kinematics of the faulting is supported by the observed transtensional left-lateral strike-slip regime in the region of tectonic depression of Hazar Lake. [ABSTRACT FROM AUTHOR]