Article

Lake Hazar Basin: A Negative Flower Structure on the East Anatolian Fault System (EAFS), SE Turkey

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Abstract

The East Anatolian Fault System ( EAFS) is a 30-km-wide, 700-km-long and NE-trending sinistral strike-slip megashear belt between the Anatolian platelet in the northwest and African-Arabian plates in the southeast. It is located between Karliova County in the NE and Karatas ( Adana)-Samandag ( Antakya) in the SW. In the Lake Hazar region, the EAFS consists of five fault zones. These are, from north to south, the Elazig fault zone, the Uluova fault zone, the Sivrice fault zone, the Adiyaman fault zone and the Lice-Cermik fault zone; in previous studies only the Sivrice fault zone has been reported to be part of the EAFS. The 2-4-km-wide and 180-km-long Sivrice fault zone contains the master fault of the system. It bifurcates into several sub-fault zones and isolated faults resulting in a 5-km-wide, 32-km-long, active lensoidal depression bounded by a series of short to long and curved fault segments with considerable amounts of normal-slip component, particularly on the southern margin. This strike-slip depression was previously reported and interpreted to be a classical pull-apart basin or rhombgraben basin originating from a left step-over located in the northeastern corner of Lake Hazar. In contrast to this earlier interpretation, our detailed field geological mapping of active faults indicates that there is no any left stepover at the northeast corner of Lake Hazar. In lieu of this, the master fault of the EAFS bifurcates into two substrands nearby Kartaldere village in the east which then run in a SW direction across Lake Hazar resulting in two sub-parallel lensoidal depressions separated by an intervening horst. This strike-slip geometry is here termed a negative flower structure. This interpretation is supported by basin-ward curved boundary faults with considerable normal-slip component of movement and by the bathymetry of Lake Hazar. Back-tilted fault blocks, uplifted and dissected Plio-Quaternary terrace conglomerates, fan-delta deposits and associated syn-sedimentary structures indicate that neotectonic infill of the basin has accumulated under the influence of a strike-slip tectonic regime. The left-lateral strike-slip amount and the vertical throw amount accumulated along the Sivrice fault zone are 9 +/- 1 km and 1317 +/- 10 m, respectively. These values yield strike- and vertical-slip rates of 4 mm/yr and 0.5 mm/yr, respectively, along the Sivrice fault zone. However, the slip rates along the EAFS must be greater because the EAFS around Lake Hazar consists of five fault zones which all share the slip rate.

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... On the other hand, there are several permanent inlets and ephemeral creeks that drain the northern and southern catchments, providing water and clastic sediments to the lake (Figure 1b). Different models have been proposed for the evolution of the Hazar Basin and its current relationship to the EAFZ (Hempton et al., 1983;Aksoy et al., 2007;Khalifa et al., 2018). However, the recent interpretation of Garcia-Moreno et al. (2010) based on the relationships of various morphotectonic structures along the lake floor proposed that Lake Hazar Basin is a pull-apart basin. ...
... The basin has been described as an active pull-apart basin (Şengör et al., 1985; Çetin et al., 2003). In the Quaternary, the western part of the lake was discharged by the Kürkçayı River and alluvial fans of diverse size extending parallel to the fault (Aksoy et al., 2007;Eriş et al., 2018a) lower Cretaceous Guleman ophiolites, upper Cretaceous Elazığ magmatics, the Maastrichtian-upper Paleocene Hazar Group, the middle Eocene Maden Group, and Plio-Quaternary and Quaternary alluviums. Outcrops of the Elazığ magmatics and the Maden Group can be observed around the Kürkçayı River and in the vicinity of alluvial fans at the western part of the lake (Figures 1c and 2). ...
... This finding is consistent with the results of previous studies. According to Aksoy et al. (2007), Eriş et al. (2013), and Eriş et al. (2018b), Lake Hazar deposits are contributed by the Kürkçayı River and alluvial fans and the Elazığ magmatics and Maden Group rocks at the western part of the lake. These rocks are mostly of mafic composition (Ural et al., 2015;Ertürk et al., 2018), which is also reflected in clay mineralogy. ...
... The accumulated overall offsets along the EAF vary between an upper range of 27-33 km that is recorded by geological features and the length of the Golbaşi strike-slip basin Bulut et al., 2012), and 15-22 km that is defined by drainage channels offsets on individual fault segments (Hempton, 1987;Bulut et al., 2012). Studies based on the geologic and geomorphic data along the EAF provide slip rates of between 6 and 11 mm/yr (Arpat and Şaroğlu, 1975;Wastaway, 1994;Kiratzi, 1993;Yürür and Chorowicz, 1998;Çetin et al., 2003;Aksoy et al., 2007;Herece, 2008;Emre, 2013, Yönlü et al., 2013), whereas the GPS studies provide a constant slip rate ~10 mm/yr along the whole EAF (Reilinger et al., 2006;Mahmoud et al., 2013;Aktuğ et al., 2016). ...
... On the other side, some researchers (e.g. Koçyiğit andBeyhan (1998) andKaymakcı, et al., (2006)) suggested a different hypothesis about the Malatya -Ovacık Fault zone activity. They argued that the Malatya-Ovacık Fault is tectonically active at present and its a part of the present motion between the Anatolian/Arabian plates. ...
... Geomorphic indices, provide a means to help assess the tectonic activity/deformation along active faults, allowing sections of the fault to be dividing into stretches of relative tectonic activity (Bull and McFadden, 1977;Rockwell et al., 1985). Geomorphic analysis has previously been successfully applied to many tectonically active areas, including Central America (Wells et al., 1988), California (Lifton and Chase, 1992), Southern Italy ( The Adıyaman Fault was mapped by Aksoy et al. (2007), but few studies have been undertaken along the Adıyaman Fault despite it being an ideal area to examine the relative tectonic activity/uplift within a continental transform setting. We apply quantitative geomorphometric methods to assess its tectonic activity and how deformation varies along its length. ...
Thesis
Summary: The transform Arabian/Anatolian plate boundary is at the origin of active tectonic structure elements that initiate large and destructive earthquakes. The aim of this thesis is to improve our knowledge and understanding of the fault behavior and deformation remarks by analyzing surface deformation along the East Anatolian Fault (EAF) that is a morphologically very distinct and seismically active left-lateral strike-slip fault that extends for ~400 km forming the Arabian/Anatolian plate boundary in southeastern Turkey. Together with its conjugate the North Anatolian Fault (NAF), the EAF helps accommodate westward escape of the Anatolian plate from the Arabian/Eurasian collision zone. In this thesis, we study morphotectonics and tectonic activity of the EAF and its splay Adıyman Fault (AdF) using the most important tectonic geomorphology indexes and analyzing different satellite images within the Arabian/Anatolian plates deformation zone. The core parts of the thesis focus on the study of morphotectonic indexes along the EAF, examining the geological offsets along the Erkenek Segment of the EAF through analyzing ASTER satellite images, relative tectonic activity assessment of the AdF, and geological and tectonic mapping along the AdF using Landsat 8 satellite images. The methods used in this thesis work are divided into two parts; the first part describes the importance of the tectonic geomorphology applications as a very useful tool to examine the interplay between tectonic and surface processes that shape the landscape in regions of active deformation and at time scales ranging from days to millions of years. It also presents a review of the most effective morphotectonic indexes (e.g., Mountain front Sinuosity; valley-floor with to valley floor-height; Hypsometric analysis) that are used to evaluate the tectonic activity along the study region. The second section gives a brief view about the application of remote sensing techniques in geology and tectonics and how the techniques have a great power to assess the different tectonic features and trace the structural elements along any active zone. Also, it presents the characteristics of the different satellite data (ASTER and Landsat 8 (OLI)) with the revision of the different method that we used in this study (e.g. Band Ratio Composite and Minimum Noise Fraction Analysis). The morphotectonic features along the East Anatolian Fault (EAF) are examined for the first time to provide insights into the nature of landscape development and better understanding of variations in tectonic activity and fault evolution. Several geomorphic indices, namely mountain front sinuosity, valley-width to valley-height ratio, stream length-gradient index, basin asymmetry factor, drainage density, and hypsometric analysis are obtained from digital elevation models. We show that mountain front sinuosity varies from 1.01 to 1.46 on five segments. The mean ratio of valley-width to valley-height along the five segments ranges from 0.11 to 1.32, which is well correlated with the mountain front sinuosity values. The stream length-gradient index values are between from 50 and 350 along the studied segments. Analysis of the basin asymmetry factor of 18 catchments gives values from 1.88 to 26.25 are examined along the study fault zone and we present the basin asymmetry factor with values from 1.88 to 26.25. The drainage density values of the studied catchments range from 3.5 to 5.6. Finally, the hypsometric analysis index of the 18 catchments records high, intermediate, and low relative tectonic activity. The results show that all geomorphic indices are remarkably uniform along the entire fault length, thus implying that its development was essentially coeval along its length, and supporting the view that the present-day Arabian/Anatolian plate boundary (delimited by the EAF) jumped eastwards from the Malatya-Ovacik Fault Zone at ~3 Ma. This is in a good agreement with the nearly uniform geological offsets and the present-day slip rate of ~10 mm/yr along the entire fault as determined by GPS measurements. The Erkenek Segment is one of the most active and prominent splays of the East Anatolian Fault. To reveal any potential geological offset geology along the AdF is refined by remote sensing techniques. This is because, mapping the geology at high spatial resolution along this segment with conventional mapping techniques is highly challenging due to the complex tectonics and the abundant number of different lithological units of varying spatial extent. Therefore, in this study, we applied image spectral rationing techniques by using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data along the Erkenek Segment. Images created with band ratios with 1/3-1/9-3/9, 7/3-1/7-3/5 and 9/5-5/3-3/1 are found to be remarkably useful for detailed lithological mapping and hence detecting the geological offsets along this section of the fault. Thus, these ASTER band-ratio images can be used for the lithological mapping along the whole EAF and on other regions in the world with similar lithological and geomorphological conditions. Geomorphic indices that include mountain-front sinuosity, valley floor width-tovalley height ratio, catchment asymmetry factor, hypsometric integrals and curves, and drainage density are calculated to evaluate the relative tectonic activity along the Adıyaman fault. Each geomorphic index is classified into three classes and averaged to define an index for relative tectonic activity (RTA) to allow the Adıyaman Fault to be divided into categories of low, intermediate and high RTA. The results confirm that the Adıyaman Fault is an active fault with intermediate Quaternary tectonic activity, suggesting that it is of minor importance in accommodating plate boundary deformation, consistent with recent crustal motions determined by GPS studies. Nevertheless, it is worthwhile to note that the Adıyaman Fault still poses a significant seismic hazard for the region despite its relatively lower tectonic activity. Independent Component Analysis (PCA and ICA) and Minimum Noise Fraction Analysis (MNFA) techniques of the Landsat 8 are applied to study the Adıyaman Fault. It is shown that the lithologic units, fault patterns, and morphological and structural features can be mapped highly accurately by using spectral-matching techniques in regions where rocks are well exposed. Inspection of all possible band combinations indicates that PCA 134 and 231, and ICA 132 band combinations give the best false-color composite images for identifying the rock units and contacts. Analysis of MNFA band combinations shows that MNFA 521 band combination also is robust for discriminating the rock units particularly Quaternary clastic units (colluvium/alluvium). MNFA band 1 alone provides the best image to trace the tectonic and structural elements in the study area. The new up-to-date lithologic map of the Adıyaman Fault that we produce upon to the interpretation of processed OLI images reveals several river channels offset and beheaded by the Adıyaman Fault, verifying its Quaternary activity. This study demonstrates that, when used with the OLI data, the PCA, ICA, and MNFA are very powerful for lithological and structural mapping in actively deforming tectonic zones, and hence can be applied to other regions elsewhere in the world where the climate is arid to semi-arid, and the vegetation cover is scarce. In generally this study presents the help of the tectonic geomorphology and remote sensing applications to evaluate the tectonic activities of a major plate boundary fault and a minor fault within the Arabian/Anatolian deformation zone. Improving our tectonic understanding of the active regions requires accurate tectonic measurements and data analysis. It so important to link the morphotectonic analysis with the different surface displacements, slip rates, and major seismic events in order to create a complete scenario about the deformation story of the active regions. Also, the new developed remote sensing methods with high-resolution images are required to go deep and gain the most benefits of applying these techniques for geology and tectonics purposes.
... still in our day susceptible to recurring losses at every significant earthquake not only on the EAF but also on any nearby active faults. Koçiğit and Aksoy documented some active, parallel or sub-parallel neighboring faults as the Elazig, Uluova, Adıyaman, and Lice-Cemik (Koçyiğit et al., 2003;Aksoy et al., 2007). Among these, the AF is the most prominent and longest EAF splay, which is located south of the tectonic depression of Hazar Lake. ...
... About 6 km south of Hazar Lake another extensional crustal unit, the plain of Bermaz, is located and is cut through by the AF in NE-SW direction. In a study by Aksoy et al. (2007) described Hazar Lake as a negative flower formation, with a splay of subsidiary faults including normal vertical components. In other words, the listric faults found inward from southern shore of the lake exhibit a "step-like morphology" firmly signifying extension, which is normal faulting (Aksoy et al., 2007). ...
... In a study by Aksoy et al. (2007) described Hazar Lake as a negative flower formation, with a splay of subsidiary faults including normal vertical components. In other words, the listric faults found inward from southern shore of the lake exhibit a "step-like morphology" firmly signifying extension, which is normal faulting (Aksoy et al., 2007). This morphology can be produced either by the presence of geometric constraints or depth variations of the rheology. ...
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Article
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.
... Arpat and Şaroğlu (1972) defined 22 km offsets on the Maastrichtian mudstone in the Göynük valley, and 27 km offsets along the Palu-Lake Hazar area. İnceöz and İnce (1999) and Aksoy et al. (2007) suggest 9 km offset for the Palu-Lake Hazar region. Çelik (2008) proposed 30 km offset in the middle Eocene Maden Comp. ...
... In many studies related to the age of the EAF (Herece and Akay, 1992;Şaroğlu et al., 1992;Çetin et al., 2003;Aksoy et al., 2007;Çolak et al., 2012;Köküm andİnceöz, 2018, Köküm, 2019), the initiation of slip on the EAF is believed to be no older than the late Pliocene (~ 3.6 my). The slip rate of the EAF using different methods has variously been reported as 4 to 35 mm/year. ...
... The slip rate of the EAF using different methods has variously been reported as 4 to 35 mm/year. Considering the age of the EAF, and lithological and morphological offsets along the fault, the long-term slip rate is calculated as 4-11 mm/year (Arpat and Şaroğlu, 1975;Öncel, 2000;Çetin et al., 2003;Aksoy et al., 2007;Çelik, 2008;Herece, 2008). From moment summations of significant earthquakes between 1955-1990Taymaz et al. (1991 calculated the slip rate as 25-35 mm/year. ...
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Article
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.
... In this respect, the EAFZ forms the other border of the Anatolian plate on the land with the NAFZ. The EAFZ, which has a length of 580 km between Karlıova and Hatay, plays a very active role in the geodynamic evolution of the Anatolian block and in the seismicity of Turkey (Arpat and Şaroğlu, 1972;Mc Kenzie, 1976;Taymaz et al., 1991;Herece and Akay, 1992;Şaroğlu et al., 1992;Nalbant et al., 2002;Aksoy et al., 2007;Bulut et al., 2012;Kartal and Kadiroğlu, 2013;Bulut, 2017;Demirtaş and Erkmen, 2019). ...
... The number 8 shows the segment where the May 1, 2003 Bingöl earthquake occurred. Hempton, 1985;Dewey et al., 1986;Allen et al., 2004;Herece and Akay, 1992;Herece, 2003;Aksoy et al., 2007;Demirtaş and Erkmen, 2019). According to the geological data, the age of the EAFZ is expressed as the Upper Pliocene and the average slip rate is 5 -8 mm/year (Herece, 2003, Demirtaş andErkmen, 2019). ...
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Article
The East Anatolian Fault Zone (EAFZ) is one the main tectonic elements of Turkey, which borders the Anatolian plate from the east. EAFZ, which is NE-SW direction, consists of many fault segments. In the historical and instrumental period, many damaging earthquakes occurred, the largest being 6.8 (Ms) as the 1971 Bingöl earthquake. The last magnitude 6.6 (Ml) (Mw = 6.8) earthquake occurred on January 24, 2020 in Elazığ - Sivrice Hazar - Sincik segment of EAFZ. However, considering the historical and instrumental activity, it is seen that many fault segments are silent. In this study, the silent and active segments, and their seismic velocity (as % Vp and Vp) and attenuation pattern (as Q-1 p) are determined in order to determine the earthquake behavior of EAFZ in the near future. From the results obtained by using the data of the earthquakes that occurred from 2007 to the end of 2019, it was clearly determined that the velocity and attenuation increased on the Hazar - Sincik segment. It has been determined that Vp is 4.08-8.2 km/sec, Q-1 p is ± 0.005 and the frequency dependency varies between 0 - 1.08 along the zone. The variation of velocity and attenuation on the segments where the earthquake occurred and in the silent section were revealed.
... Alpha particles emitted by radon gas produces a track on the plastic detectors. By counting the tracks over a given time the radon concentration (Bq/m 3 ) is calculated [6,8]. In these observations, it is accepted that there is a natural balance between radon and its other products. ...
... The amount of damage, the magnitude of scraped track and the level of being etched, depends on the amount of linear energy transfer rather than the way it is tracked by the charged particle. The total amount of energy lost by the particle in the environment plays an essential role in determining the magnitude of scraped blank on detector depending on applied etched conditions [6,8]. ...
... We also observe one moderate and several smaller earthquakes south of the town of Sivrice, consistent with a minor, southern splay fault observed by Bulut et al. (2012). The largest of these has a normal faulting mechanism, perhaps related to development of Lake Hazar basin (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
... Almost all lie north of the EAF surface trace, consistent with the aftershock distribution obtained by Melgar et al. (2020) and with the inferred northward fault dip. The easternmost aftershock studied here has a distinctive normal component, consistent with interpretations of the Lake Hazar basin as a releasing bend or pull-apart (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
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Article
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.
... We also observe one moderate and several smaller earthquakes south of the town of Sivrice, consistent with a minor, southern splay fault observed by Bulut et al. (2012). The largest of these has a normal faulting mechanism, perhaps related to development of Lake Hazar basin (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
... Almost all lie north of the EAF surface trace, consistent with the aftershock distribution obtained by Melgar et al. (2020) and with the inferred northward fault dip. The easternmost aftershock studied here has a distinctive normal component, consistent with interpretations of the Lake Hazar basin as a releasing bend or pull-apart (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
... We also observe one moderate and several smaller earthquakes south of the town of Sivrice, consistent with a minor, southern splay fault observed by Bulut et al. (2012). The largest of these has a normal faulting mechanism, perhaps related to development of Lake Hazar basin (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
... Almost all lie north of the EAF surface trace, consistent with the aftershock distribution obtained by Melgar et al. (2020) and with the inferred northward fault dip. The easternmost aftershock studied here has a distinctive normal component, consistent with interpretations of the Lake Hazar basin as a releasing bend or pull-apart (Aksoy et al., 2007;Duman & Emre, 2013;Garcia Moreno et al., 2011). ...
... In the region, this collision event resulted in crustal thickening, thrust tectonism and development of complex fault systems (Sungurlu et al., 1985), such as the EAFZ (Fig. 1). The EAFZ, a NE-SW trending mega shear belt nearly 30 km wide and 700 km long (see inset in Fig. 1), consists of several faults around the study area (Aksoy et al., 2007;Çolak et al., 2012). ...
... In the study area, Upper Pliocene-Pleistocene Palu formation and Quaternary alluvial deposits unconformably overlie all the preceding geological formations (Çetindağ, 1985). The Palu formation can be characterized as a fluvio-lacustrine sedimentary sequence (Kerey and Türkmen, 1991) that was deposited as a result of intense tectonic activity in the region (Aksoy et al., 2007). Quaternary alluvium is characterized by poorly sorted unconsolidated materials, ranging in size from pebble to silt and clay (Sungurlu et al., 1985). ...
Article
The Uluova basin aquifer system (UBAS), comprised of fractured/karstic rock and multilayer basin-fill aquifers, provides water for both domestic and agricultural needs in the Elazığ province (Eastern Turkey). Although, the UBAS has been subject of large-scale hydrological modifications and controversial water management practices since late 1950s, thus far no studies have examined basinwide implications of such human perturbations in an integrated manner. In this study, GIS, geostatistics, R-mode factor analysis (R-mFA) and geochemical modeling techniques were employed to unravel the factors controlling the distribution and sources of arsenic (As) and selected potentially toxic elements (PTEs) in the stream sediment-soil and groundwater-surface water systems of the UBAS. As revealed by the results from R-mFA, three geogenic factors (F1: Clay minerals and Fe–Mn oxyhydroxides, F2: Weathering of parent materials, and F3: Sulfide oxidation in mineralized zones) govern the geochemical dynamics of the PTEs in the stream sediment/soil media. In stream sediment and soil samples, especially Ni, Cr, and Co presented significant enrichment relative to upper continental crust average composition, whereas As contents were relatively low, varying from 0.3 to 13 mg kg−1. Factors extracted from the combined water dataset (F1: Groundwater salinization and arsenic mobilization, F2: Clay minerals and Fe–Mn oxyhydroxides, F3: pH and redox conditions, and F4: Aquifer oxygenation and nitrate contamination) accounted for 72.59% of the total variance. Water-rock interaction (e.g. sulfide oxidation, carbonate dissolution, silicate hydrolysis, adsorption-desorption, ion exchange, and evaporite dissolution), dilution/mixing with fresh/saline water components, evapoconcentration, and human induced perturbations causing internal salinization and oxygenation of the UBAS were the key mechanisms controlling the chemistry of waters and mobilization of As. In the UBAS, majority of As-rich water samples are confined to central-northern half of the basin and typically display high levels of dissolved O2, inorganic oxyanions (HCO3−, SO42− and of Si, B, Mo, Sb and V) and alkaline pH. Oxidation of sulfides (e.g. pyrite and arsenopyrite) found within the highly fractured Elazığ magmatics in the upland areas at north and subsequent competitive adsorption-desorption processes occurring under alkaline, oxidizing and high ionic strength aquifer conditions along the downgradient groundwater flow path play a pivotal role in the As-enrichment in the UBAS. As concentrations ranged between 0.02–367.2 ug L−1 in groundwater, 0.13–4842 ug L−1 in spring water, and 0.04–31.1 ug L−1 in the stream water samples, of which 20.83% exceeded the WHO provisional guideline value. In the water samples, As occurs mainly as As(V) species (HAsO42− and H2AsO4−), indicated by the Eh-pH diagram and speciation calculations. The results of this study have shown that As enrichment in the UBAS can be attributed to both geogenic processes and anthropogenic activities that have modified the basin hydrology/hydrochemistry.
... The Bitlis Suture Belt is a complex that can be defined as the continent-continent and continent-ocean collision boundary, extending from the southeast of Turkey to the Zagros Mountains in Iran. It is characterized by a N-S trending compressional tectonic regime located to the east of the Karlıova triple junction (Aksoy et al. 2007;Demirci 2019;Bayik 2021). In addition to these, one of the important tectonic structures in Turkey is the Western Anatolian Graben System. ...
Article
Significant loss of life and property has occurred as a result of many destructive earthquakes in both historical and instrumental periods in Turkey, which is located on the Alpine-Himalayan seismic belt. Past local earthquakes are an excellent tool to predict potential earthquakes in any region. Within the scope of this study, seismic parameters were obtained in the light of current data for a total of 62 earthquake epicenters with Ms ≥ 6 that occurred in the instrumental period in Turkey. Comparisons between seismic parameters were made on the last two earthquake hazard maps used in Turkey. In addition, the measured actual peak ground acceleration values for 16 earthquakes whose data can be accessed were compared with the current peak ground acceleration values as specified in the current Turkish Seismic Design Code. In order to compare the effectiveness of seismicity hazard map specified in previous and current Turkish Seismic Design Code, structural analysis of a reinforced-concrete building was carried out by using both the measured and current acceleration values according to the last two earthquake hazard maps. It has been determined that there are differences between the measured and proposed peak ground acceleration for some earthquakes. There are significant differences between the expected target structure displacement values as a result of structural analyses.
... One fundamental step to define and discriminate neotectonic regions is the determination of the slip rates across faults and block boundaries. While direct field measurement of the fault offsets at fault trace provides invaluable information about the activity of the faults (Aksoy et al., 2007;Arpat and Şaroğlu, 1972;Hempton, 1985), the local nature of this type of observations, their relatively low precision and the difficulty of its application at broader deformation zones makes them infeasible for full quantification of the slip rates. For a study at this scale covering the whole of Turkey and surrounding regions, no consistent set of geologic slip rates is available. ...
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Article
This paper aims to present a new neotectonic perspective concordant with the seismic activities in Turkey and surrounding regions. The neotectonic structures have been re-evaluated mainly by using focal mechanism solutions and high-resolution satellite (Google Earth) images. Southeast Anatolian Wedge explains thrust/blind thrust and asymmetrical folding relationship in SE Turkey, Syria, and Northern Iraq. The neotectonic structures of Turkish-Iranian Plateau are enlightened by the rhomboidal cell model which creates a base to determine multiple intersection points between the region-wide left- and right-lateral shear zones. The releasing stepover between the North Anatolian Fault Zone and Southeast Anatolian-Zagros Fault Zone plus their connections with the Northeast Anatolian Fault Zone and East Anatolian Fault Zone are described in a more meaningful way with the Anatolian Diagonal concept. It also clarifies the role of left-lateral shear zone in the west-southwest movement of Anatolian plate and its relationship with the Aegean and Cyprus arcs. A neotectonic region under the influence of NW-SE contraction is determined between the North Anatolian, Eskişehir, and Kırıkkale-Erbaa fault zones in which Elmadağ-Eldivan and Abdüsselam pinched crustal wedges and Beypazarı Blind Thrust Zone are developed. A new route for the southern branch of the North Anatolian Fault Zone is determined between Bolu and Değirmenlik (Milos) Island in the Aegean Sea via Mudurnu, Bursa, Balıkesir, and İzmir. All main neotectonic structures mentioned in this paper are evaluated by the elastic dislocation modelling and new neotectonic provinces are suggested.
... The geology of the Hazar region has long been the subject of numerous studies because of its location on an active East Anatolian Fault Zone (EAFZ) (Ar-pat & Şaroğlu 1972;Tatar et al. 1995;Aksoy et al. 2005;Aksoy et al. 2007;Çelik 2008;Garcia Moreno et al. 2011). NE-SW trending EAFZ is a 30 km wide, 700 km long zone between the Anatolian and Arabian plates. ...
... earthquake, 20 cm fall observed on the northwest block of the fault showed a small vertical component (Kürçer et al., 2020). This vertical component indicates that the negative flower structure formed due to the extensional stress proposed for the Hazar Lake (Aksoy et al., 2007) continues in this area. Similarly, the morphology of this area reflects the active tectonics of EAFZ. ...
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: The Eastern Anatolian Fault Zone (EAFZ), having a prominent place in the tectonic evolution of the Eastern Mediterranean, is a structural element of tectonic indentor due to the convergence between the African-Arabian plates and the Eurasian Plate. This study investigates the central part of EAFZ between Doğanyol (Malatya) and Çelikhan (Adıyaman). The geometry of the fault and the morphotectonic structures were determined by the field studies. Moreover, fault-slip data are measured according to the fault planes along the deformation zone for paleostress analysis. The paleostress analysis revealed three deformation phases that developed from the Late Eocene to the present due to the convergence between the Arabian Plate and the Anatolian Block. The first deformation phase is characterized by NW-SE compressional stress between Late Eocene and Late Oligocene periods. The second deformation phase is related to N-S compressional stress from the Middle Miocene to Pliocene. The most recent deformation phase shows the strike-slip faulting under the NNE-SSW compressional stress from the Late Pliocene to the present. The EAFZ developed during the last phase of these deformation stages. In addition, elongated ridges parallel to the fault, sinistral offsets of drainage networks, linear valleys, and fault terraces observed along the segment show that the study area exhibits active tectonic morphology of the EAFZ. The distribution of seismic activity that occurred during and after the recent mainshock (24 January 2020, Sivrice-Doğanyol earthquake) is compatible with the geometry of the segment and confirms strongly the active tectonics of the segment. Key words: East Anatolian Fault Zone, paleostress analysis, deformation phase, Sivrice-Doğanyol earthquake
... the Lake Hazar as a result of negative flower structure proposed by Aksoy et al., 2007;Moreno et al., 2011]. ...
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In this study, we investigated the main features of the causative fault of the 24 January 2020, Mw 6.8 Elazığ earthquake (Turkey) using seismological and geodetic data sets to provide new insight into the East Anatolian Fault Zone (EAFZ). We first constrained the co-seismic surface deformation and the rupture geometry of the causative fault segment using Interferometric Synthetic Aperture Radar (InSAR) interferograms (Sentinel-1A/B satellites) and teleseismic waveform inversion, respectively. Also, we determined the centroid moment tensor (CMT) solutions of focal mechanisms of the 27 aftershocks using the regional waveform inversion method. Finally, we evaluated the co-seismic slip distribution and the CMT solutions of the causative fault as well as of adjacent segments using the 27 focal solutions of the aftershocks, superimposed on the surface deformation pattern. The CMT solution of the 24 January 2020Elazığ earthquake reveals a pure strike-slip focal mechanism, consistent with the structural pattern and left-lateral motion of the EAFZ. The rupture process of the Elazığ event indicated that the rupture is started at 12 km around the hypocenter, and then propagated bilaterally along the NE-SW but mainly toward the southwest. The rupture slip has initially propagated toward the southwest (first 10 s) and northeast (4 s), and again toward the southwest (9 s). Maximum displacement is calculated as 1.3 m about 20 km southwest of the hypocenter at 6 km depth (centroid depth). The rupture stopped to down-dip around 20 km depth toward the southwest. The distribution of the slip vectors indicates that the rupture continued mostly through a normal oblique movement. Most of the moment release was released SW of the hypocenter and the rupture reached up to around 50 km. The focal mechanisms of analyzed 27 aftershocks show strike-slip, but mostly normal and normal oblique-slip faulting with an orientation of the tensional axes (NNE-SSW), indicating a normal oblique-slip, “transtensional” stress regime, parallel-subparallel to the strike of the EAFZ, consistent with SW-rupture directivity and co-seismic deformation pattern. Finally, based on the co-seismic surface deformation compatible with the distributional pattern of normal focal solutions, normal and normal oblique-slip focals of the aftershocks evidence the rupture-parallel pull-apart basin activation as a segment boundary of the left-lateral strike-slip movement of the EAFZ.
... Karlıova-Antakya arasında değişik özellikte olan birbirlerini tamamlayan birçok sol yönlü doğrultu atımlı faydan oluşan zon, Doğu Anadolu Fay Sistemi olarak adlandırılmıştır [29]. DAFZ, yaklaşık 30 km genişliğinde, 700 km uzunluğundadır [30,31]. Sivrice depremi bu sessizliği bozmuş ve yeni bir deprem serisi mi başlıyor sorusunu gündeme getirmiştir. ...
Article
Depremlerin, yapılar üzerindeki etkilerini azaltmak adına yapı-zemin-deprem etkileşiminin gerçekçi olarak ortaya konulabilmesi önemlidir. Bu çalışma kapsamında, Türkiye Bina Deprem Yönetmeliğinde yer alan beş farklı yerel zemin koşulu dikkate alınarak sekiz katlı örnek bir çelik yapı için yapısal analizler gerçekleştirilmiştir. Bu güncel yönetmelik ile birlikte bölgesel bazda kullanılan tasarım spektrumları yerini sahaya özgü spektrumlara bırakmıştır. Bu değişimin yapısal analizlere etkisini koymak adına, 24 Ocak 2020 Sivrice (Elazığ) (Mw=6.8) depremin en çok etkilediği iki yerleşim birimi olan Sivrice (Elazığ) ve Pütürge (Malatya) için elde edilen tasarım spektrumları kullanılarak, her iki yerleşim birimi için de yerel zemin koşulları için analizler ayrı ayrı gerçekleştirilmiştir. Çalışmada ayrıca iki yerleşim biriminin de içerisinde yer aldığı Doğu Anadolu Bölgesinin depremselliği ve son deprem hakkında bilgiler verilmiştir. Bu çalışma sahaya özgü tasarım spektrumlarının ve yerel zemin koşullarının çelik yapılardaki etkisini ortaya koymak adına yapılmıştır.
... During this transitional period, a series of deformations such as the thickening of crust, regional tectonic uplift, formation of folds with E-W-trending axis, thrust to reverse faults, resetting of new drainage system, disappearance of marine conditions, development of short-to long-term stratigraphic gaps and prominent calc-alkaline volcanic activity occurred (Şengör and Kidd, 1979;Innocenti et al., 1980;Dewey et al., 1986;Şaroğlu and Yılmaz, 1986;Yılmaz et al., 1987;Ercan et al., 1990;Koçyiğit and Beyhan, 1998;Koçyiğit et al., 2001;Koçyiğit, 2013). The contractional deformation and development of fold-thrust belts continued until the latest Pliocene, and then this transitional period was replaced by the emergence of a new tectonic regime (prominent strike-slip faulting-related tectonic regime) (Koçyiğit et al., 2001;Aksoy et al., 2007;Çolak et al., 2012;Koçyiğit, 2013;Koçyiğit and Canoğlu, 2017). It is evidenced by the occurrence of a series of inversions such as the deformation style of faulting, types of geological structures, the nature of sedimentation and basin formation, geochemical characteristics of the volcanic activity (e.g., from calc-alkali nature to prominent alkali composition) and the nature of seismic activity. ...
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Article
The variation in the motion sense of Anatolian platelet in Aegean Sea resulted in a strike-slip tectonic regime and related neotectonic domain, the central to northern Aegean neotectonic province, which also includes both western Marmara Sea and Biga Peninsula. Our study focuses mostly on the Gülpınar-Tuzla earthquake area located at the southwestern tip of Biga Peninsula, which is controlled by the southern major strand of the North Anatolian Fault System (NAFS). The strand consists of two sections, the onshore Biga and offshore Babakale-Skyros sections. Both sections are seismically very active. The Gülpınar-Tuzla earthquake area is composed of the Paleozoic metamorphic rocks, the Oligo-Miocene granitoid pluton, Lower-Middle Miocene calc-alkalic volcanic rocks and the Upper Miocene-Pliocene sedimentary sequence. All of these rocks, which formed and deformed (folded to tilted) in palaeotectonic period, are overlain with an angular unconformity by the Quaternary neotectonic basin fill, that is nearly flat-lying except for the faulted basin margins. Both the onshore and offshore sections of the southern strand are linked to each other in terms of the structures characterizing the Babakale pull-apart basin and the Gülpınar-Tuzla earthquake area. The latter is shaped by the NE-trending Gülpınar (GFZ) and Yenice-Gönen Fault Zone (YGFZ), the ENE-trending Edremit fault zone (EFZ), the WNW-trending Tuzla Fault Zone (TFZ) and three strike-slip basins (Ayvacık, Behramkale and Tuzla basins) developed along them. Some segments of both the TFZ and GFZ were reactivated by the occurrences of seven moderate-to small-sized independent earthquakes and related aftershocks over 2760. Five of the independent earthquakes have an origin of oblique-slip normal faulting, while the rest two seismic events are strike-slip faulting in origin. Focal mechanism solution diagrams of these two groups of earthquakes reveal that the Gülpınar-Tuzla area is under the control of a strike-slip neotectonic regime, which commenced in Early Quaternary time owing to the major inversion in extensional palaeotectonic regime. This is also supported by the palaeostress analysis of slip-plane data measured on fault slickensides. The uniform slip rates on both the YGFZ and EFZ are 10.8 mm/yr and 7.3 mm/yr, respectively.
... Turkey's most critical tectonic characteristics are the Aegean Arc, the West Anatolian Graben Complexes, the North Anatolian Fault (NAF), the East Anatolian Fault (EAF), the North East Anatolian Fault and the Bitlis Thrust Zone. The EAF constitutes an essential part of Turkey's tectonic structure, Anatolia 4-13 mm on the due westward movement of the plates/year being left-lateral characters (Hempton 1985;Arpat and Saroglu 1972;Dewey et al. 1986;Allen et al. 2004;Westaway 1994;Aksoy et al. 2007;Duman and Emre 2013;Bulut 2017). ...
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In this study, the magnitude of an earthquake in the East Anatolian Fault (EAF) of Turkey are predicted based on previous earthquakes whose magnitudes are four or more by two-time series methods, namely autoregressive integrated moving average (ARIMA) and singular spectrum analysis (SSA). These methods are quite new in seismology despite being successful techniques in other branches of science. We use ARIMA and SSA models to train and predict the mean and maximum values of the earthquakes' magnitudes due to seismological events between years 1900 and 2019. 447 earthquake magnitudes between 1900 and 1995 are used for training models, and then 447 magnitudes between 1995 and 2019 are taken into account for testing. The root mean square error (RMSE) is calculated to evaluate the accuracy of each model. The results demonstrate that the SSA model is better than the ARIMA model to predict the earthquake magnitude. Hence, for the years 2020 to 2030 the magnitude of an earthquake is forecasted using the SSA model. The result shows that the highest magnitude of earthquake is forecasted for the year 2021 in magnitude level of 4.0-5.9.
... Cetin et al. (2003) reported in their study of paleoseismology conducted on the EAFZ that the EAFZ is locked and that the energy accumulated by this tectonic unit may be discharged in the future. Aksoy et al. (2007) emphasized that the lateral slip velocities are 4 mm/year and the vertical slip velocities are 0.5 mm/year along the Sivrice Fault Belt, which shows the left-lateral slip character. Sertcelik (2012) reported the lowest Coda values on the EAFZ where Elazığ is included. ...
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Article
A destructive earthquake (Mw 6.8) occurred at Sivrice-Elazığ on the East Anatolian Fault Zone (EAFZ) on 24th January, 2020, causing loss of life and property. During the period of historical and instrumental seismology, destructive earthquakes have occurred at certain periodic intervals on the EAFZ, and micro-earthquake activity is also a frequent tectonic event. In this study, time-dependent four-dimensional tomography images of the Hazar-Sincik segment, one of the six segments of the EAFZ that produced the Sivrice earthquake, were obtained for the first time using the local earthquake tomography method. Synthetic tests show that data sets from before and after the Sivrice earthquake can produce reliable results in the Hazar-Sincik segment up to 20 km deep. Low Vp and Vp/Vs values were observed before the Sivrice earthquake, and an increase in Vp/Vs rates was detected after the Sivrice earthquake. Low Vp and Vp/Vs values along the Bitlis-Zagros Thrust Belt indicate that this area may present a high earthquake hazard. Very low Vp velocities on the Erkenek segment, which has produced destructive earthquakes in the past make us think that this region is still loaded with stress and that potential earthquakes in the future are likely. The results show that Vp and Vp/Vs characteristics change radically after a major earthquake. The reasons for these changes include the evolution of underground porosity and permeability values after major earthquakes. Detecting the area of seismological changes underground with time-dependent four-dimensional tomographic images can provide an important basis for earthquake prediction research.
... Furthermore, the rate of motion along the NAFZ has changed with time from 0 cm/year to present velocity (Ş engör et al., 2005; Ş engör and Zabcı, 2019). Although GPS-based slip rate estimation on EAFZ changes between 9 and 15 mm/yr (Oral, 1994;Barka and Reilinger, 1997;Reilinger et al., 1997;McClusky et al., 2000;Cavalié and Jónsson, 2014), long term slip rate varies between 4 and 6 mm/yr (Westaway and Arger, 1996;Aksoy et al., 2007;Yönlü et al., 2012). The discrepancy between present and short-to-long term slip rate inevitably proves that it is not reasonable to assert a deformation model by assuming that the slip rate of the faults do not change over millions of years. ...
Article
Collision of the Arabian and Eurasian plates has resulted in uplift of the Turkish-Iranian Plateau, where debate continues over how post-collisional convergence is being converted to strain. The internal deformation models of the plateau have taken into account the distribution of deformation in the NW-trending Bitlis-Zagros Mountain Range (BZMR), the southern boundary of the collision. The western end of the BZMR is marked by contrasting topographic relief resulting from the coupling of tectonic and erosional processes. This region providing an excellent record for undertaking quantitative analysis which can improve our understanding of its tectonic evolution. Mountain front analyses reveal that each fault segment located in front of the western BZMR falls within the limits of Class-1 that corresponds to an uplift rate of >0.5 mm yr−1. Hypsometric and basin asymmetry analysis were analyzed for 93 drainage basins, indicating that weakly to moderately eroded basins can be moderately to strongly asymmetric but show no uniform tilting direction. Channel concavity, integral and knickpoint analyses suggest that, apart from the thrust fault that represents the margin of the collision zone, there is no pronounced single geological constraint that causes differential tectonic uplift and furthermore implies that the effect is distributed across multiple different structures. The findings of this study suggest that continuous lower rate horizontal displacement has occurred in this region since the onset of collision, but also indicates that the western end of the BZMR represents a zone of higher convergence, in which shortening is being converted to the vertical plane strain.
... DAFS Arap levhasının kuzeye doğru hareketi ile Anadolu levhasının batıya doğru hareketi sonucunda, yaklaşık 600 km uzunluğunda ve 30 km genişliğinde Kuzeydoğu-Güneybatı yönlü sol yanal doğrultu atımlı bir transform levha sınırı oluşturmaktadır [24][25][26]. DAFS, Karlıova ile Bingöl arasında "Karlıova-Bingöl Segmenti (~65 km)", Palu ile Hazar Gölü arasında "Palu-Hazar Gölü Segmenti (~50 km)", Hazar Gölü ile Sincik arasında "Hazar-Sincik Segmenti (~85 km)", Çelikhan ile Gölbaşı arasında "Çelikhan-Gölbaşı Segmenti (~50 km)", Gölbaşı ile Türkoğlu arasında "Gölbaşı-Türkoğlu Segmenti (~90 km)" ve Türkoğlu ile Antakya arasında "Türkoğlu-Antakya Segmenti (~145 km)" yer alan 6 farklı yapısal segmentten (Şekil 1a) oluşmaktadır [27][28][29][30][31][32] Bir depremin şartlı olasılığı gelecek t yılda ve son depremden sonra geçen te aralık zaman içerisinde Eşitlik 2 ile tanımlanmıştır. farklı deprem kataloglarıyla kullanılmış ve şartlı olasılık değerleri hesaplanmıştır [13][14][15][16][17][18][19][20][21][22][23]. ...
... Elde edilen sonuçlar yorumlanarak öneriler yapılmıştır. [10,11]. Bunların yanı sıra, ülkemizdeki önemli tektonik yapılardan biri Batı Anadolu Graben Sistemi'dir. ...
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Bir bölgenin depremselliği, yerel zemin koşulları ve yapısal özellikler yapıların deprem etkisi altındaki davranışlarını ve risklerini belirlemede kullanılan önemli parametrelerdir. Yapılar ile ilgili analizlerde o bölgenin depremselliği, spektrum eğrileri ile ifade edilebilmektedir. 2019 yılında yürürlüğe giren Türkiye Bina Deprem Yönetmeliği ile noktaya özel spektrum eğrileri kullanılmaya başlanmıştır. Bu çalışma kapsamında Türkiye’deki yedi farklı coğrafik bölgeden birer il seçilerek coğrafik konumun hem deprem parametrelerine hem de yapı performans hesaplamalarını hangi düzeyde etkilediği ortaya konmaya çalışılmıştır. Ankara, Antalya, Diyarbakır, Erzurum İstanbul, İzmir ve Samsun illeri için 50 yılda aşılma olasılığı %10 (tekrarlanma periyodu 475 yıl) olan ve Türkiye Bina Deprem Yönetmeliği’nde DD-2 olarak belirtilen yer hareket düzeyi ile yerel zemin sınıfı ZE olarak dikkate alınmıştır. Her il için kısa periyot harita spektral ivme katsayısı, en büyük yer ivmesi, en büyük yer hızı, yerel zemin etki katsayıları, tasarım spektral ivme katsayıları ile yatay ve düşey elastik spektrum eğrisi için hesaplamalar yapılmıştır. Çalışma ile farklı geometrik konumlarda bulunan fakat aynı zemin özellikleri ve yer hareketi olmasına rağmen deprem parametrelerinin değişimi incelenmiştir. Coğrafik konumun yapı performans hesaplamalarına etkisi ortaya koymak adına tüm illerde aynı yapısal özelliklere sahip yedi katlı betonarme bir yapı seçilmiştir. Seçilen örnek betonarme yapı için her il için analizler gerçekleştirilmiştir. Yapı analizinde zemin özelliklerinin dikkate alındığı statik adaptif itme analiz kullanılmıştır. Elde edilen tüm sonuç değerleri karşılaştırılmıştır. Coğrafik konum değişikliği hem deprem parametrelerini hem de yapısal analiz sonuçları doğrudan etkilemektedir. Çalışma, Türkiye Bina Deprem Yönetmeliğinin sahaya özel deprem parametrelerinin bir kazanım olduğu sonucunu ortaya çıkarmıştır. Herhangi bir noktada yerel zemin koşulları ve yapısal özellikler aynı olsa bile bölgenin depremsellik öğelerinin dikkate alınması gerekmektedir.
... The East Anatolian Fault Zone (EAFZ), which forms the seismic source of the Sivrice (Elazığ)-Doğanyol (Malatya) earthquake, is a major sinistral strike-slip fault zone in Turkey. It starts at the Karlıova triple junction, where the EAFZ meets the North Anatolian Fault Zone, in the northeast and runs southwestward for about 600 km through Bingöl, Palu, Hazar Lake, Pütürge, Sincik, Narlı, Türkoğlu regions and extends up to the İskenderun Bay in the Mediterranean Sea area (e.g., Arpat and Şaroğlu 1972;Hempton and Dunne 1984;Aksoy et al. 2007;Khalifa et al. 2018) (Fig. 2a and b). The fault zone comprises several short left-lateral fault segments and associated strike-slip basins; Lake Hazar is one of those basins. ...
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On Friday, January 24, 2020 at 20.55:11 local time (17:55 UTC), an earthquake with a magnitude of Mw = 6.8 has occurred in Sivrice district of Elazığ (Eastern Turkey). Focal mechanism solution is consistent with pure left-lateral strike-slip faulting; the location of the epicenter and fault mechanism suggest deformation along the Pütürge segment of the East Anatolian Fault Zone. A 10-day fieldwork was carried out along the Pütürge segment to study surface deformation; the geometry of the surface rupture and other seismic geomorphological structures were mapped and studied in detail. The field data are also correlated with satellite images. This paper, therefore, presents classification of seismic geomorphological structures and discuss intimate relationship between fault geometry and stress field in the region. Seismic geomorphological deformation and related features of the Sivrice (Elazığ) earthquake are observed in the area between Gezin (Elazığ) and Ormaniçi (Pütürge) villages; they are classified into two as seismotectonic and seismo-gravitational features. Field observations confirm that seismo-gravitational structures develop along both Gezin-Sivrice–Doğanbağı and Doğanbağı–Çevrimtaş–Ilıncak–Koldere–Ormaniçi sections of the Pütürge segment, while surface rupture is mapped as seismotectonic structure only along the Doğanbağı–Çevrimtaş–Ilıncak–Koldere–Ormaniçi section. Small-scale landslides, rock falls, feather cracks along asphaltic roads, and laterally discontinues ground failure-related features are common seismo-gravitational structures that developed along the fault zone. In addition, small-scale lateral spreading and liquefaction structures are common especially in areas where fault-perpendicular streams meet the Karakaya Dam reservoir. The surface rupture is mapped as stepping and overlapping en échelon fractures along elongated pressure ridges between Çevrimtaş and Doğanbağ villages, to northwest of Ilıncak village, along 1.5-km-long pressure ridge between Topaluşağı and Doğanyol, across the elongated hill that developed on an alluvial fan to the northwest of Doğanyol and in the area between Koldere and Ormaniçi villages. Surface fractures deforming the pressure ridges are all aligned parallel to the long axes of the ridges and display reverse components that give rise to small-scale pop-up structures. Interferometric SAR (DInSAR) studies indicate a 10-cm uplift in the northwestern block of the fault and a 6-cm subsidence in the southeast block. The difference in vertical movements between two blocks of the fault is interpreted to suggest that at least 30-km-long section of the Pütürge segment in the area between southwest of Sivrice and Pütürge is broken during the main shock. Although the focal mechanism solution of the main shock gives pure left-lateral strike-slip faulting, there is no significant left-lateral displacement observed during the fieldwork. This can be explained by the following: (1) left-lateral strike-slip displacement was not able to reach the surface; (2) left-lateral torque movement of the fault around a vertical axis during the earthquake, (3) restraining bend nature of the Pütürge segment, or (4) the presence of Pütürge metamorphics along the fault strike. It is also important to note that along most part of the Pütürge segment where surface rupture is observed, talus, colluvial or alluvial fan sediments are exposed; unconsolidated and/or poorly consolidated nature of these sediments may also be counted as one of the main reason for not observing horizontal displacement on the surface. When we compare these surface deformations with the surface ruptures that occurred in the last 100 years in Turkey, we suggest that the formation of the surface deformations is variable depending on: (1) the fault type and the state of regional stress, (2) the magnitude of the earthquake, (3) the duration time of the earthquake and (4) the geomorphologic feature of landscape in relation to the lithologic and structural features of the rock units along the active fault zone.
... The stratigraphy and geological evolution of the Elazığ area have been summarised by Yazgan (1984), Yazgan and Chessex (1991), Turan and Bingöl (1991), Bingöl and Beyarslan (1996), Aksoy et al. (1996Aksoy et al. ( , 2005Aksoy et al. ( , 2007, Cronin et al. (2000aCronin et al. ( , 2000bCronin et al. ( , 2005Cronin et al. ( , 2007a, Çelik (2003, 2013), Beyarslan and Bingöl (2018), Bingöl et al. (2018), andYılmaz (2018). A geological map of the Elazığ area is shown in Figure 1, summarising the work on the evolution of the area by Turan and Bingöl (1991), Aksoy et al. (1996), Cronin et al. (2000aCronin et al. ( , 2000b and Çelik (2013). ...
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Deep-water channels are well-exposed along the northern margin of the east-west oriented Late Paleocene to Oligocene Elazığ Basin of eastern Turkey. The deep-water slope channel complexes are characterised by their association with prominent normal faults, where they seem to have controlled their geometries at the northern margin. The channels were fed by coarse-grained sediment shed by subaqueous gravity flows such as high and low-density turbidity currents, and both cohesive and noncohesive debris flows, from elevated hinterland across narrow shelves and through canyons and gullies into the channels. The faulting and subsequent folding along the northern basin margin created a significantly irregular deep-water slope, and these gravity flows were deflected around, and ponded against this topography. The nature of the impact of seafloor topography, created both before and during channel activity, was examined to create a scheme that documents the range of such effects. Detailed field mapping in this semidesert area shows that these slope channel complexes were strongly controlled by block fault topography generated during early basin evolution in the Late Paleocene, and again during fold development from thrust nappe emplacement during basin filling in the Late Middle Eocene when the Hazar- Maden Basin closed in the south. Four styles of slope channel complex-fold interaction have been recognised: deflection, blocking, diversion, and confinement. In each style of interaction, folding and faulting controlled both channel complex planform geometry and architectural style of the channel fills. In addition to seafloor topography inherited from these earlier phases of compression, subsequent gravitational collapse on the northern basin margin also created normal fault-bound blocks that locally controlled turbidity current pathways and channel complex orientation. It has also been shown that the orientation of the slope channel complexes within mudprone slope sequences has later controlled the orientation of younger fold axis in the Middle Eocene. The study illustrates very well-exposed examples of complex seafloor topography generated by compressional and extensional tectonics, and the impact this has had on slope channel complex evolution.
... Although it has also strike-slip deformation characteristics and a similar seismicity rate, the EAFZ is not as well-known as the NAFZ (Aksoy et al., 2007) Figure 1. a) Location of the area investigated (modified from Bozkurt, 2001), b) shaded relief map, active faults (Şaroğlu et al., 1992) and focal mechanism solutions of some events (Kalafat et al., 2009) in the region, c) geological map of KTJ and its surroundings (modified from Dilek and Sandvol (2009) Figure 1a). ...
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A dataset obtained from six broadband stations of 111 small- to moderate-sized local events that occurred between 2010 and 2018 was analyzed to reveal the frequency-dependent seismic body (body-Q) and coda (coda-Q) wave attenuation characteristics of three tectonic branches of the Karlıova Triple Junction: the Varto Fault Zone (VFZ), North Anatolian Fault Zone (NAFZ), and East Anatolian Fault Zone. The magnitude range was between 2.8 and 6.1 with shallow (<10 km) focal depths. The maximum station-event distance was selected as not to exceed 120 km. Frequency-dependent Qc functions were determined using the single back-scattering model with four lapse time lengths (20, 30, 40, 50 s) while the extended coda normalization method was performed to estimate the body wave attenuation functions for seven central frequencies varying from 1.5 Hz to 18 Hz. The minimum and maximum Qp values were 7 at 1.5 Hz for the VFZ and 739 at 18 Hz for the NAFZ, respectively. Qs values were observed between a minimum of 26 for VFZ and maximum of 1259 for NAFZ. Additionally, coda-Q results show a strong lapse time dependency between Q0 and n; exhibiting a decrease in n by an increase in Q0 , with an ascending lapse time. Comparing the three subregions of the Karlıova Triple Junction, VFZ appears to have a significantly higher attenuation for all Q types and Qs/Qp ratios while the NAFZ has relatively low attenuation.
... The Adıyaman fault is a leftlateral strike-slip fault located in the continental East Anatolian Fault (EAF) zone. The Adıyaman fault was mapped by Aksoy et al. (2007), but few studies have been undertaken along it despite being an ideal area to examine the RTA/uplift within a continental transform setting. We apply quantitative geomorphometric methods to assess its tectonic activity and to examine how deformation varies along its length. ...
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Article
The left-lateral strike-slip Adıyaman fault is located in eastern Turkey within the plate boundary deformation zone between Arabia and Anatolia. The Adıyaman fault is a major splay from the East Anatolian Fault (EAF), one of the most important tectonic structures in the Eastern Mediterranean region. These faults are consequence of the collision between the Arabian and Anatolian plates and the resulting westward tectonic escape of Anatolia. Although the EAF has been intensively studied since its discovery in the late 1960s, little is known about the Adıyaman fault and its tectonic activity. In this study, we extract geomorphic indices including mountain-front sinuosity (Smf), valley floor width-to-height ratio (Vf), stream length-gradient (SL), catchment Asymmetry Factor (AF) and hypsometric integrals and curves (HI and HC) to evaluate the relative tectonic activity of the Adıyaman fault. These three geomorphic indices (AF, HI, and HC) are averaged to define an index for Relative Tectonic Activity (RTA) that allows the Adıyaman fault to be divided into categories of low, moderate and high RTA. The results confirm that the Adıyaman fault is an active fault with high to moderate Quaternary tectonic activity. However, this fault is of minor importance on accommodating plate boundary deformation, as evidenced by the recent crustal motions determined by GPS studies. Nevertheless, it is worthwhile to note that the Adıyaman fault still poses a significant seismic hazard for the region despite its relatively moderate tectonic activity.
... This group was selected because it is a rare example of a Ponto-Caspian genus with one species, Cornigerius lacustris Spandl, 1923, endemic to freshwater Lake Hazar. This rift lake, situated on the east Anatolian plateau, near the city of Elaziğ, occupies the bottom of a fault, is ca 5 km wide, 30 km long, has a maximum depth of 210 m, and is of Pliocene age (Aksoy et al., 2007). Pleistocene fluctuations in depth occurred and reached up to 90m. ...
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Cornigerius species are endemic to the Ponto-Caspian, with the exception of Cornigerius lacustris, which is endemic to freshwater Lake Hazar in the Euphrates basin. However, the barcoding fragment of the cytochrome c subunit I (COI) of animals from the type locality shows less than 1 % divergence with Black Sea and less than 2% with Caspian Lake C. maeoticus, the oldest and most widespread species of the genus. Black Sea and Caspian Lake animals show 1.5 % divergence. We therefore place the origin of the Hazar population in the Black Sea. Combined with a variable morphology, we also conclude that C. lacustris is a synonym of C. maeoticus, as already suspected by its describer. Dating the ‘lacustris’ population is difficult, but it has been there for at least a century.
... East Anatolian Fault Zone (EAFZ) passes through the study area and it forms a 5-6 km wide zone in the middle portion of the Lake Hazar Basin. For the purpose of this study, the pre-Pliocene rocks exposed in the Lake Hazar Basin are termed as basement rocks (Figure 1), which include Paleozoic-Mesozoic Pötürge metamorphics, Jurassic-Lower Cretaceous Guleman ophiolites, Senonian Elazığ igneous rocks, Maastrichtian-Upper Paleocene Hazar and the Middle Eocene Maden Group (Aksoy et al., 2007). Climatologically, the study area is situated in a continental climate zone. ...
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Conference Paper
In this study, groundwater samples collected from 51 different locations within the Lake Hazar Basin were analyzed using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) for determination of the concentrations of trace elements including arsenic, cadmium, copper, manganese, lead, zinc, nickel, and chromium. Minimum and maximum concentrations (in ppb) of the selected trace elements in water samples were found as: 0.00-2.08 for As, 0.01-0.15 for Cd, 0.05-111.35 for Cu, 0.06-311.44 for Mn, 0.01–2.56 for Pb, 1.73-896.11 for Zn, 0.09-14.21 for Ni, and 0.05-3.39 for Cr. According to this data, copper and manganese concentrations in some water samples were found in excess of regulatory safe levels recommended for drinking water.
... Arpat and Şaroğlu, 1972;Şengör, 1980;Dewey et al., 1986;Şaroğlu et al., 1992;Herece and Akay, 1992;Güneyli, 2002;Koçyiğit, 2003; https://doi.org/10.1016/j.gexplo.2018.07.006 Received 4 October 2017; Received in revised form 31 May 2018; Accepted 12 July 2018 Aksoy et al., 2007). ...
... Nemrut is a dormant polygenic strato-volcano in Eastern Turkey, located 10 km northwest of the city Tatvan which is in the western shore of Lake Van. Nemrut caldera is located in the collision zone of the Arabian and Eurasian tectonic plates, which determines the seismic and volcanic activity in the region (Ercan et al., 1990;Yılmaz et al., 1998;Aksoy et al., 2007). The volcano is named after King Nimrod who is said to have ruled this area in about 2100 BC. ...
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Abstract. Geotourism is one of the most important tourism sectors that has rapidly developed and become widespread in recent years. Geotourism is defined as tourism that sustains or enhances the distinctive geographical character of a place—its environment, heritage, aesthetics, culture, and the well-being of its residents. The purpose of geotourism is to recognize and protect these natural structures of public, as well as contributing to local and regional development through the emerging species. Geotourism incomes have begun to increase in the total tourism incomes of the countries. There are many places in Turkey that can be considered as possible areas of geotourism. In this scope; Cappadocia fairy chimneys, Manisa Kula volcanic area, Denizli Pamukkale travertines and Bitlis Nemrut Caldera were studied.
... Previous studies of the EAFS, Turkey's second active fault, focused on the mapping fault geometry and identifying segmentations (Arpat and Şaroğlu, 1972;Jackson and McKenzie, 1984;Şengör et al., 1985;Lyberis et al., 1992;Şaroğlu et al., 1992;Nalbant et al., 2002;Çetin et al., 2003;Westaway, 2003;Yılmaz et al., 2006;Aksoy et al., 2007;Duman and Emre, 2013). However, they have not provided satisfying information in terms of the deformation mechanism and kinematic features of faults. ...
Article
The East Anatolian Fault System (EAFS) is an intra-continental strike-slip fault associated with the collision of the Arabian plate with the Anatolian plate in the Alp-Himalaya system. In this study, the northern part of the EAFS, was studied. We measure more than two-hundred fault slip data (strike, dip, striation and slip sense for each fault) in eighteen different localities to make paleostress reconstruction of the related area. Several criteria are taken into consideration in order to reveal chronology of faulting such as superimposed slickenlines, age of the affected strata and syndepositional faults. Our results show three different deformation stages from the Middle Eocene to today in the study area: (1) The NW-SE extensional tectonic, oldest stage, became effective in Middle Eocene-Middle Miocene; (2) the NNE-SSW compressional tectonic become effective in Late Miocene-Early Pliocene; (3) the strike-slip tectonic, youngest stage, has been effective since Late Pliocene. The maximum compressive stress (σ1) orientation averaged around N25°E and N15°E for Stage 2 and Stage 3, respectively. This ca. 100 rotation of the maximum compressive stress (σ1) orientation may be related to the formation of the strike-slip faults concluded changing in the stress orientations between σ3 and σ2 in the Late Pliocene.
... Another group (2) (Turkey) measured radon in the Sivrice Fault Zone (point "Si", Fig. 1c), which is a segment of the East Anatolian Fault System (EAFS). The Sivrice Fault Zone (SFZ) is 2-to 6-km-wide, 180km-long and NE-trending sinistral strike-slip fault zone that is located between the district of Palu in the northeast and the district of Yarpuzlu in the southwest (Aksoy et al., 2007;Şahin, 2009). The descriptions of geological and radiation characteristics of area are also made by Baykara and Doğru (2006), Doğru et al. (2003Doğru et al. ( , 2001. ...
Article
Results of measurements of radon around of the Black Sea are shown. Radon stations in zones of active faults were placed. Simultaneous hourly measurements of soil radon in 2005 were carried out in the Sivrice Fault Zone that is a segment of East Anatolian Fault System, in the town of Tbilisi (Georgia) and in the South Russia. In 2008 simultaneously hourly measurements of soil radon were carried out in the Western Caucasus (Russia) and in the Mytilene Island (Greece). In 2013 radon in underground waters simultaneously in midday was measuring in Crete (Greece), in the Pamukkale geothermal region (Southwest Turkey) and in the Western Caucasus. Measurements of radon concentration in the points located around of the Black Sea have shown identical regularities in changes of the data. Influence of meteorological, tidal and solar factors on changes of water radon concentrations and soil radon concentrations was observed in all researches points. But this influence was insignificant. Seismological application of observed results also was considered. Various mathematical methods of definition of anomaly in the radon data during earthquakes were considered. During researches in the Black Sea region basically earthquakes with M from 2.0 up to 5.0 and in a depth about 10 km were occurred. For these earthquakes method of daily subtraction of the data of the next and previous day was used. This method has allowed solving a problem with a choice of average value. Probability up to 0.69 (number of earthquakes with radon anomalies/total number of earthquakes) of detection of radon anomalies before earthquakes was achieved applying this method. Changes of radon maps before regional earthquakes were also observed. The frequency analysis of variations of the radon data on the basis of the Wavelet analysis was carried out. Occurrence of the short periods (about 2 days) was observed during regional earthquakes.
... Nemrut is a dormant polygenic strato-volcano in Eastern Turkey, located 10 km northwest of the city Tatvan which is in the western shore of Lake Van. Nemrut caldera is located in the collision zone of the Arabian and Eurasian tectonic plates, which determines the seismic and volcanic activity in the region (Ercan et al., 1990;Yılmaz et al., 1998;Aksoy et al., 2007). The volcano is named after King Nimrod who is said to have ruled this area in about 2100 BC. ...
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Preprint
Geotourism is one of the most important tourism sectors that has rapidly developed and become widespread in recent years. Geotourism is defined as tourism that sustains or enhances the distinctive geographical character of a place-its environment, heritage, aesthetics, culture, and the well-being of its residents. The purpose of geotourism is to recognize and protect these natural structures of public, as well as contributing to local and regional development through the emerging species. Geotourism incomes have begun to increase in the total tourism incomes of the countries. There are many places in Turkey that can be considered as possible areas of geotourism. In this scope; Cappadocia fairy chimneys, Manisa Kula volcanic area, Denizli Pamukkale travertines and Bitlis Nemrut Caldera were studied.
Article
Frequency-magnitude distribution was investigated in Elazig city and the surrounding area (coordinates ranging from 38.1° N to 39° N for latitudes and 39° E to 40° E for longitude) to reveal the present-day crustal stress within the region. For this study, a complete set of 5603 earthquakes of Md ≥ 1 from 1 January 2000 to 31 August 2020 were localized from the Bogazici University, Kandilli Observatory and Earthquake Research Institute, Regional Earthquake-Tsunami Monitoring Center (KOERI) catalogue. For the whole study region, spatial mapping of the frequency-magnitude distribution was thus produced. The frequency-magnitude distribution (b-value) for seismicity within the study area was not homogeneous. Outstanding variations in the b-value were detected with b ranging from b ≈ slightly more than 0.3–2. In this region, low b-values are mostly dominant in the region except for a few local areas. This study also shows that accumulated stresses are high particularly at the Pütürge segment in contrast to the fault drawn in the south, which represents the main thrust belt that runs through Hani-Lice and stretches to Çüngüş. As expected, stress accumulation in reverse faults is fairly higher. However, the sharing of the tension formed in the compression zone of the Arabian Plate and the Anatolian plate (i.e. stress partitioning in a sense), results in a low share in the reverse fault belt.
Article
The eastern Mediterranean region is in the embryonic stages of continent-to-continent collision, and has a pristine Miocene–Quaternary tectonic and stratigraphic record which is not overprinted by pervasive collisional processes often seen in more mature orogens, thus can serve as a model for ancient orogenic belts. This manuscript is based on the interpretation and mapping of ~38,500 km of seismic reflection profiles across the eastern Mediterranean Sea, and provides a holistic synthesis of the tectonic and sedimentary evolution of the region since the Miocene. The synthesis is presented using three regional tectonic maps (time slices at pre-Messinian Miocene, Messinian and uppermost Messinian–Quaternary) and two regional isopach maps (time slices at Messinian and uppermost Messinian–Quaternary), six tectonostratigraphic charts and six geological cross-sections across the forearc region north of the greater Cyprus Arc. These data showed that the southern margins of the Eurasian Plate in the Miocene and the Aegean–Anatolian Microplate during the Pliocene–Quaternary following the extrusion of Anatolia have changed gradually from subduction of the Afro–Arabian Plate to collision, first the Arabian Plate with the Eurasian Plate along the Bitlis–Zagros fold-thrust belt, and now the incipient collision between the African Plate and the Aegean–Anatolian Microplate along the greater Cyprus Arc, including the Florence Rise. During the pre-Messinian Miocene, the strain appears to be by minor oblique slip on thrusts, but during the uppermost Messinian–Quaternary the strain becomes partitioned between thrusts and new strike-slip faults, with ultimately the strike-slip faults cutting across the dying thrusts. The Messinian interval was marked by Mediterranean-wide tectonic quiescence, during a period of remarkable variations of base-level and the deposition of shallow-water evaporite succession within deep basins. During the uppermost Messinian–Quaternary 5–6 regionally arcuate convex to the south oblique fault zones developed across the eastern sector of the forearc region. The eastern limbs of these prominent fault zones exhibit sinistral strike-slip and normal-sense dip-slip, whereas the western limbs of the fault zones exhibit dextral strike slip and normal- and reverse-sense dip-slip. In the east, these fault zones link with the horse-tail splays of the East Anatolian fault zone. These oppositely moving strike-slip zones create distinctive V-shaped conjugate fault patterns across Central Anatolia extending southward into the central portion of the eastern Mediterranean region north of the Cyprus Arc. It is speculated that these V-shaped conjugate fault patterns represent the upper crustal expression of an incipient minor slab tear immediately west of the Island of Cyprus. The Anaximander Mountains (sensu lato) and the Rhodes and Finike basins developed across the western sector of the forearc at the junction of the Hellenic and Cyprus arcs. These structures show extreme tectonic activity during the uppermost Messinian–Quaternary, with major subsidence of the Rhodes and Finike basins, and concomitant uplift of the Anaximander Mountains.
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Conference Paper
A destructive earthquake occurred near Sivrice district of Elazığ with magnitude Mw=6.8 on January, 24, 2020, at local time 20:55. The epicenter of the earthquake is located Doğanyol sub-segment of the 85 km long “Sivrice-Pütürge” segment of the East Anatolian Fault which is 600 km left lateral strike slip fault extending from Karlıova in the northeast to the Hatay in the southwest. After the main shock, 1600 aftershock occurred that magnitudes vary between 0.8 and 5.1 until 31 January. 22 of these earthquakes are 4.0 and above. Aftershocks extending along the Sivrice-Pütürge Segment represent linearity in the NE of the main shock, while clustering in the SW. The focal mechanism solutions of M ≥ 4.0 earthquakes along the Sivrice-Pütürge Segment have provided a left lateral strike-slip faulting solution and indicate a very good compatibility with the general tectonics of the region. After the Mw=6.8 main shock, in order to observe potential co-seismic deformation, it is benefited from ESA Copernicus Sentinal 1A-B data (C-band ~6 cm wavelength). Including pre and post-earthquake, 2 images were evaluated on ascending Track 116 by the help of the GmtSAR Parallel Program. According to obtained interferogram, it is confirmed that deformations were observed in the section of the East Anatolian Fault that includes the "Sivrice-Pütürge" segment. It has been observed that the estimated rupture is on the Doğanyol sub-segment of the Sivrice-Pütürge Segment of EAFS. According to the Coulomb stress analysis performed to understand the stress change in the region after the earthquake, stress accumulation was observed ranging from 1 to 5 bars in the northwest of Pütürge District and Sivrice District and Hazar Lake. When InSAR, aftershocks, coulomb and focal mechanism data and Sivrice-Pütürge part are overlapped in terms of segmentation; it is thought that the rupture that occurred in the January 24 earthquake happened deep in the sub-segment of Doğanyol, which is approximately 25-30km long, between the middle and southwestern aftershocks cluster. In the 24 January earthquake, it should be investigated in detail whether the earthquake rupture has surfaced or whether the surface rupture remains underwater in the sub-segment of Doğanyol where the Fırat River has moved 10 km left laterally.
Conference Paper
A destructive earthquake occurred near Sivrice district of Elazığ with magnitude Mw=6.8 on January, 24, 2020, at local time 20:55. The epicenter of the earthquake is located Doğanyol sub-segment of the 85 km long “Sivrice-Pütürge” segment of the East Anatolian Fault which is 600 km left lateral strike slip fault extending from Karlıova in the northeast to the Hatay in the southwest. After the main shock, 1600 aftershock occurred that magnitudes vary between 0.8 and 5.1 until 31 January. 22 of these earthquakes are 4.0 and above. Aftershocks extending along the Sivrice-Pütürge Segment represent linearity in the NE of the main shock, while clustering in the SW. The focal mechanism solutions of M ≥ 4.0 earthquakes along the Sivrice-Pütürge Segment have provided a left lateral strike-slip faulting solution and indicate a very good compatibility with the general tectonics of the region. After the Mw=6.8 main shock, in order to observe potential co-seismic deformation, it is benefited from ESA Copernicus Sentinal 1A-B data (C-band ~6 cm wavelength). Including pre and post-earthquake, 2 images were evaluated on ascending Track 116 by the help of the GmtSAR Parallel Program. According to obtained interferogram, it is confirmed that deformations were observed in the section of the East Anatolian Fault that includes the "Sivrice-Pütürge" segment. It has been observed that the estimated rupture is on the Doğanyol sub-segment of the Sivrice-Pütürge Segment of EAFS. According to the Coulomb stress analysis performed to understand the stress change in the region after the earthquake, stress accumulation was observed ranging from 1 to 5 bars in the northwest of Pütürge District and Sivrice District and Hazar Lake. When InSAR, aftershocks, coulomb and focal mechanism data and Sivrice-Pütürge part are overlapped in terms of segmentation; it is thought that the rupture that occurred in the January 24 earthquake happened deep in the sub-segment of Doğanyol, which is approximately 25-30km long, between the middle and southwestern aftershocks cluster. In the 24 January earthquake, it should be investigated in detail whether the earthquake rupture has surfaced or whether the surface rupture remains underwater in the sub-segment of Doğanyol where the Fırat River has moved 10 km left laterally.
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27 Aralık 2020'de Hazar (Sivrice) Gölü'nün hemen kuzeybatısında büyüklüğü 5.5 olan depremi inceleyince bu yazıyı yazmaya karar verdim. Ne ilgisi var dediğinizi hissediyorum. Biz meslekte bu gölü 'fay gölü (sag pond)' olarak tanımlarız. O nedenle ilgisi var. Aşağıda size bu ilgiyi fazla teknik ayrıntıya girmeden açıklamaya çalışacağım.
Article
The 24 January 2020 (Mw=6.8) earthquake with epicentre in Elazığ (Sivrice) on the East Anatolian Fault Zone caused loss of life and property. The information was given about the seismotectonic setting and regional seismicity along this fault zone and aftershock activity and ground motion data of this earthquake. Earthquake parameters were obtained for five different earthquake stations which were closer to the epicentre. Horizontal and vertical design spectra were obtained for the geographic locations for each earthquake station. The obtained spectra for the earthquake epicentre were compared with selected appropriate attenuation relationships. The damages after earthquake were evaluated via geotechnical and structural aspects. This study also aims to investigate the cause effect relationships between structural damage in reinforced concrete and masonry structures, respectively. The lack of engineering services was effective on the amount of damage in masonry structures. Insufficient reinforcement and concrete strength, dimensions and inadequate detailing increased the amount of damage in reinforced concrete structures. Importance should be given to negative parameters that may weaken the defence mechanisms of structures for earthquake resistant structural design.
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In this study, it is aimed to determine the trace element contents of groundwater and surface waters in Hazar Lake Basin (Elazig) and to evaluate these elements in terms of human health. For this purpose, concentrations of trace elements such as arsenic (As), cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb), zinc (Zn), nickel (Ni), and chromium (Cr) in water samples taken from 51 different sites in the basin were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The lowest and highest concentrations of the selected trace elements in water samples (ppb) were determined as 0.01-2.08 for As, 0.01-0.15 for Cd, 0.05-111.35 for Cu, 0.06-311.44 for Mn, 0.01-2.56 for Pb, 1.73-896.11 for Zn, 0.09-14.21 for Ni, and 0.05-3.39 for Cr. According to these results, Cu and Mn concentrations in some water samples were found to be higher than the recommended standard values for drinking water.
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Research
East Anatolian Fault System and trench studies in Gölormanı
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In this study geochemistry of clastic rocks from the Palu Formation, Eastern Turkey has been investigated. Samples were collected from two sections within the Palu Formation: the Hacımekke section which is composed of alluvial fan deposits and the Hacısamdere section consisting of basin infill material deposited within a braided river exposing parallel to the Eastern Anatolian Fault Zone. X-ray diffraction patterns show that Hacımekke samples are comprised by calcite, clay, mica, quartz, feldspar, dolomite, and serpentine, and Hacısamdere samples are composed of feldspar, clay, mica, amphibole, pyroxene, calcite, and serpentine. Clay minerals of Hacımekke and Hacısamdere sections are chlorite, smectite, and illite, respectively. In both sections concentrations of Fe2O3 and MgO, CaO, MnO, Cr2O3 are enriched with respect to PAAS. This might indicate that the source rock of studied samples is not felsic continental source rocks, like PAAS. Most major, trace and rare earth elements contents of two section samples are generally similar to their catchment area. La/Sc, Th/Sc, Co/Th and Cr/Th of two sample groups reflect similar values, and show basic, neutral rocks rather than acidic rocks. Chondrite-normalized REE patterns of Hacımekke and Hacısamdere samples are characterized by LREE enrichment, relatively flat HREE pattern and no Eu negative anomaly. Chemical index of alteration indicate that chemical weathering in the source area and recycling processes have been more important for Hacımekke samples. Some samples of Hacımekke plot in arc field and other fall in the collision field. Hacısamdere samples are plotted within the arc field.
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The study area is located at Eastern Anatolian Fault Zone and at the western shore of Lake Hazar (Elazig, Turkey). This study aims to identify the hydrochemical features of groundwaters from fractured igneous aquifers and to correlate them with the alluvial aquifer’s groundwaters. The water samples were collected in April and September during the rainy and dry periods, respectively. As a result of active tectonism in this region, hard rocks have gained secondary porosity and permeability. According to major ion composition, the fractured igneous and alluvial aquifer groundwaters can be grouped into the Ca-Mg-HCO3 type, whereas the groundwaters emerging very close to the thrust fault locations can be classified as the Mg-Ca-HCO3 type. The water-rock interaction process represents the primary factor controlling the hydrochemistry of the investigated groundwaters. Generally, the alluvial aquifer’s groundwaters are characterized by low pH values. Clay minerals in the alluvial material may act as H⁺ buffers and cause decreased pH values. According to the isotopic tracers of ¹⁸O, ²H, and ³H, the spring water discharging at higher altitudes from the fractured igneous aquifer reflects rapid circulation and recharging from recent precipitation compared to alluvial aquifer groundwater. The groundwaters’ major ions fall well within the permissible limits for drinking water in Turkey. In contrast, the NO3⁻ and NH4⁺ concentrations from groundwaters, especially those recharging from fractured igneous aquifers, are very close to or in excess of the limit values. The high concentrations of NO3⁻ and NH4⁺ in groundwaters presumably result from landfills and the use of agricultural fertilizers in the study area. The surface waters (Lake Hazar and man-made wetland (MMW)) also are investigated within the scope of the hydrochemistry studies. Higher TDS, Cl⁻, and Na⁺ concentrations in the MMW reflect salinity that could result from lake water intrusion and evaporation processes.
Chapter
The River Tigris is one of the most significant rivers in the Middle East. All the landscapes drained by the river from Hazar Lake and neighbouring mountains down to the Iraqi–Syrian border in the Cizre region are mainly characterized by folded structures, often faulted, widely affecting limestone series. In this structural context, the incision of rivers shaped Jura-type and Appalachian-type morphologies. Meanwhile, tectonics has also generated rapid changes in the river network. The rapidity of post-Mio-Pliocene uplift caused deep incision of canyons into rising and thrusting folds, and preservation of a few remarkable Mio-Pliocene and Pliocene topographies. The chapter presents a geomorphological survey of the headwaters of the River Tigris, which is formed of two branches. The meeting of these branches (Maden and Birkleyin streams) downstream Eğil city forms the proper River Tigris. The paper examines the landscapes in the Euphrates–Tigris divide area where Hazar Lake is located. Landscapes in both the Maden and Birkleyin basins record the Eastern Anatolian Fault Zone activity during the Pleistocene, with epigenic canyons and meanders, dry valleys resulting from captures, and karstic systems deepening during uplift. Dams (constructed or under construction) have a profound impact in the Tigris and tributary valleys. The end of this programme will provoke the drowning of almost half the main river valley floor down to the Turkish–Syrian/Iraqi border (from Bismil to Cizre) and the loss of ancient settlements, towns and historic heritage that are located along the Tigris floodplain.
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Chapter
The multifarious landforms making up the landscapes of Turkey are largely controlled by tectonic activity since the last 11 Ma, at most 23 Ma making surface correlation by elevation alone hazardous. This “neotectonic episode” is characterized by tectonic escape that created five neotectonic provinces in the country: (1) the shortening east Anatolian province corresponds to the eastern Anatolian highlands; (2) the gently E–W-shortening north Turkish province; (3) extensional west Anatolian province; (4) the gently NE–SW-shortening and NW–SE-extending Ova Province; and (5) the border folds (Assyrides) of the northernmost Arabian Plate. In each of these provinces, the rate and history of uplift, history of climate and rock types have dictated the details of land sculpture. Volcanic landforms dominate in the east, and karst dominates in the south. The other regions display more varied morphological types controlled mainly by rock type and climate. Although Turkey is moderately endowed in fossil glacial and periglacial forms, active glaciers are few and restricted to the high mountains in the extreme south-east of the country.
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Analysis of the geologic and geophysical data from the western and northern margin of the Arabian plate combined with data from the Red Sea/ Gulf of Aden leads to an interpretation of Arabian plate motion that supports an episodic extensional history in the Red Sea and Gulf of Aden. Phase 1 extension began in medial to late Eocene and was caused by the NW propagation of the reoriented Central Indian Ridge spreading center. It stretched and thinned continental crust along numerous wrench and normal faults that reactivated preexisting structures. First-phase extension stopped when the Arabian plate terminally sutured to Eurasia in the medial Miocene and halted northward movement of Arabia relative to Africa. The combined African/Arabian plates moved north more slowly, constricting and thickening continental crust in the Bitlis/Zagros sutures while the Red Sea remained tectonically quiescent and accumulated salt. By the early Pliocene, continued northward movement was accommodated by lateral extrusion of large continental wedges north of the Bitlis/Zagros sutures. This allowed Arabia to move northward faster than Africa and reopen the Red Sea where phase 2 extension was expressed by seafloor spreading. Extension within the Red Sea/Gulf of Aden rift system has been controlled by the interactions and effects of two factors: (1) convergent processes between the north margin of the Arabian plate and the Eurasian plate to
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Detailed mapping of the Bitlis suture zone near Lake Hazar shows that it is composed of 3 tectonostratigraphic units. From S to N, these are the Puturge Metamorphic Complex, the Maden Melange, and the Elazig Igneous Complex. The Puturge Metamorphic Complex was generated by isoclinal folding and metamorphism of sediments composing the Arabian continental margin during Campanian-Maastrichtian ophiolite obduction to the S. The Elazig arc developed on the deformed margin because of subsequent S subduction of oceanic lithosphere. The arc migrated to the N, opening a back-arc basin. By the early Eocene, the back-arc basin was filling with volcaniclastics of the Maden Melange, and the Elazig arc collided with a continent to the N.-from Author
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The Tekirdag depression within the Marmara Sea in the Mediterranean region is an active, rhomb-shaped strike-slip basin along the North Anatolian fault with a basin floor at a water depth of -1150 m. New multichannel seismic reflection data and on-land geological studies indicate that the basin is forming along a releasing bend of the strike-slip fault and is filled with syntransform sediments of Pliocene-Quaternary age. The basin is bounded on one side by the North Anatolian fault and on the other side by a subparallel normal fault, which forms the steep submarine slope. In cross section the basin is strongly asymmetric with the thickness of the syntransform strata increasing from a few tens of meters on the submarine slope to over 2.5 km adjacent to the North Anatolian fault. Seismic sections also show that the slope-forming normal fault connects at depth to the North Anatolian fault, implying that the basin is completely detached from its substratum. The whole structure can be envisaged as a huge, rather flat, negative flower structure. The releasing bend of the North Anatolian fault, responsible for the formation of the basin, is flanked by a constraining bend. Along the constraining bend, the syntransform strata are being underthrust, implying a recent change in the direction of the regional displacement vector. This thrusting is responsible for the uplift of the submarine slope to a height of 924 m, possibly by a mechanism of elastic rebound. Regional geology suggests that most of the syntransform strata are lacustrine with only the topmost few hundred meters consisting of deep marine clays. The anomalous present depth of the Tekirdag depression is due to reduced Quaternary sedimentation coupled with high rates of displacement along the North Anatolian fault, which amounts to 20 mm/yr in the Marmara Sea region.
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Following the collision along the Bitlis–Zagros suture, a north–south convergence between the Arabian Platform and Laurasia has continued uninterrupted until the present. As a result, the continental crust has been shortened, thickened and consequently elevated to form the Turkish–Iranian high plateau. On the high plateau volcanic activity began during the Neogene, intensified during the late Miocene–Pliocene and continued until historical times. Large volcanic centres have been developed during the Quaternary which form significant peaks above the Turkish–Iranian high plateau. Among the Quaternary volcanoes, the major volcanic centres are Ararat, Tendürek, Suphan and Nemrut. Ararat (Ağri Daği) is the largest volcanic center and is a compound stratovolcano, consisting of Greater Ararat and lesser Ararat. The former represents the highest elevation of Anatolia reaching over 5000 m in height. Tendürek is a double-peaked shield volcano, which produced a voluminous amount of basalt lava as extensive pahoehoe, and aa flows. It has an ill-defined semi-caldera. Suphan is an isolated stratovolcano, capped by silicic dome. It represents the second highest topographic elevation in Anatolia, with a height of over 4000 m. A cluster of subsidiary cones and small domes surrounds the volcano. Nemrut is the largest member of a group of volcanoes, which trend north–south. It is a stratovolcano, having a well-defined collapse caldera and a caldera lake. Various volcanic ejecta have been extruded from these volcanic centres over the last 1 to 2 million years. The Quaternary volcanic centres, although temporally and spatially closely associated, display a wide range of lavas from basalt to rhyolite. The volcanoes have diverse compositional trends; Ararat is distinctly subalkaline, Suphan is mildly subalkaline, Nemrut is mildly alkaline and Tendürek is strongly alkaline. The major and trace element compositions together with the isotope ratios indicate that their magmas were generated from a heterogeneous mantle source. Each of the volcanic centres has undergone a partly different magmatic evolution.
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The Tethyan evolution of Turkey may be divided into two main phases, namely a Palaeo-Tethyan and a Neo-Tethyan, although they partly overlap in time. The Palaeo-Tethyan evolution was governed by the main south-dipping (present geographic orientation) subduction zone of Palaeo-Tethys beneath northern Turkey during the Permo-Liassic interval. During the Permian the entire present area of Turkey constituted a part of the northern margin of Gondwana-Land. A marginal basin opened above the subduction zone and disrupted this margin during the early Triassic. In this paper it is called the Karakaya marginal sea, which was already closed by earliest Jurassic times because early Jurassic sediments unconformably overlie its deformed lithologies. The present eastern Mediterranean and its easterly continuation into the Bitlis and Zagros oceans began opening mainly during the Carnian—Norian interval. This opening marked the birth of Neo-Tethys behind the Cimmerian continent which, at that time, started to separate from northern Gondwana-Land. During the early Jurassic the Cimmerian continent internally disintegrated behind the Palaeo-Tethyan arc constituting its northern margin and gave birth to the northern branch of Neo-Tethys. The northern branch of Neo-Tethys included the Intra-Pontide, Izmir—Ankara, and the Inner Tauride oceans. With the closure of Palaeo-Tethys during the medial Jurassic only two oceanic areas were left in Turkey: the multi-armed northern and the relatively simpler southern branches of Neo-Tethys. The northern branch separated the Anatolide—Tauride platform with its long appendage, the Bitlis—Pötürge fragment from Eurasia, whereas the southern one separated them from the main body of Gondwana-Land. The Intra-Pontide and the Izmir—Ankara oceans isolated a small Sakarya continent within the northern branch, which may represent an easterly continuation of the Paikon Ridge of the Vardar Zone in Macedonia. The Anatolide-Tauride platform itself constituted the easterly continuation of the Apulian platform that had remained attached to Africa through Sicily. The Neo-Tethyan oceans reached their maximum size during the early Cretaceous in Turkey and their contraction began during the early late Cretaceous. Both oceans were eliminated mainly by north-dipping subduction, beneath the Eurasian, Sakaryan, and the Anatolide- Tauride margins. Subduction beneath the Eurasian margin formed a marginal basin, the present Black Sea and its westerly prolongation into the Srednogorie province of the Balkanides, during the medial to late Cretaceous. This resulted in the isolation of a Rhodope—Pontide fragment (essentially an island arc) south of the southern margin of Eurasia. Late Cretaceous is also a time of widespread ophiolite obduction in Turkey, when the Bozkir ophiolite nappe was obducted onto the northern margin of the Anatolide—Tauride platform. Two other ophiolite nappes were emplaced onto the Bitlis—Pötürge fragment and onto the northern margin of the Arabian platform respectively. This last event occurred as a result of the collision of the Bitlis—Pötürge fragment with Arabia. Shortly after this collision during the Campanian—Maastrichtian, a subduction zone began consuming the floor of the Inner Tauride ocean just to the north of the Bitlis—Pötürge fragment producing the arc lithologies of the Yüksekova complex. During the Maastrichtian—Middle Eocene interval a marginal basin complex, the Maden and the Çüngüş basins began opening above this subduction zone, disrupting the ophiolite-laden Bitlis—Pötürge fragment. The Anatolide-Tauride platform collided with the Pontide arc system (Rhodope—Pontide fragment plus the Sakarya continent that collided with the former during the latest Cretaceous along the Intra Pontide suture) during the early to late Eocene interval. This collision resulted in the large-scale south-vergent internal imbrication of the platform that produced the far travelled nappe systems of the Taurides, and buried beneath these, the metamorphic axis of Anatolia, the Anatolides. The Maden basin closed during the early late Eocene by north-dipping subduction, synthetic to the Inner-Tauride subduction zone that had switched from south-dipping subduction beneath the Bitlis—Pötürge fragment to north dipping subduction beneath the Anatolide—Tauride platform during the later Palaeocene. Finally, the terminal collision of Arabia with Eurasia in eastern Turkey eliminated the Çüngüş basin as well and created the present tectonic regime of Turkey by pushing a considerable piece of it eastwards along the two newly-generated transform faults, namely those of North and East Anatolia. Much of the present eastern Anatolia is underlain by an extensive mélange prism that accumulated during the late Cretaceous—late Eocene interval north and east of the Bitlis—Pötürge fragment.
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In Eastern Anatolia, the neotectonic episode commenced with the complete elemination of the neo-Tethyan ocean floor as a result of collision between Arabia and Eurasia during Early Miocene time. After the collision, continuing convergence initiated a new tectonic regime and coeval magmatic activity. The post-collisional convergence caused crustal shortening and thickening as evidenced by regionwide development of E-W trending folds and thrusts, and conjugate strike-slip faults. The related volcanic activity has progressed in three cycles. In the initial cycle weakly-alkaline volcanic rocks were produced that are known as the Solhan volcanics. They outcrop at the western end of an E-W striking neotectonic depression called the Muş basin, which constitutes the western prolongation of the Lake Van basin. The basin is a thrust-bounded depression that developed out of an original syncline by the disruption of its limbs. The lavas of the first cycle reached the surface along N-S aligned extensional structures.In the second volcanic cycle a widespread K-type Ca volcanism occurred through crustal contribution during the Late Miocene-early Pliocene time when the continuing north-south convergence caused substantial shortening and thickening of the continental crust.The last volcanic cycle produced a thick volcanic cover consisting of rocks of alkaline affinity during the Pleistocene and the Quaternary when the thickened crust began to accommodate the ongoing north-south shortening by east-west extension after the formation of the East and North Anatolian transform faults.
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The nature of the interaction between the Anatolian, Arabian, and Af-rican plates is an important problem of northeastern Mediterranean tectonics. The Dead Sea Fault and East Anatolian Fault Zone are the most prominent structural elements in this region. The Cilician Basin, which is located at the junction of these faults, is known to have a very active seismic history. However, instrumental obser-vations have been insufficient because of the lack of an adequate local seismic net-work. To monitor ongoing seismic activity and to analyze the seismotectonics of the Cilician region (36 to 38 N, 34 to 38 E), a digital seismic network of 18 stations with velocity transducers has been operated by the Earth and Marine Sciences Re-search Institute (EMSRI) of the Scientific and Technical Research Council of Turkey (T BITAK) since 1993. No previous studies have been carried out in this region for crustal structure. An optimum 1D velocity model was obtained by using the VELEST algorithm for reliable determination of earthquake hypocenter locations. Approxi-mately 2500 earthquakes detected between 1993 and 2002 with local magnitude greater than 1.5 have been located by using this optimum velocity model. The most notable feature of the epicentral distribution is the presence of dense clusters of activity along local fault trends. The majority of hypocentral depths of the events range between 5 and 35 km. Single-fault plane solutions of reliable events were calculated in order to analyze the seismotectonic characteristics of the region. Results show that the Cilicia region constitutes a wide left lateral shearing zone that indicates a diffuse plate boundary between the African, Arabian and Anatolian Plates.
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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.
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The complex structural relationship between the East Anatolian and Dead Sea fault zones is examined, mostly based on field observations in southeastern Turkey where the two fault zones are close together. Several faults, previously poorly documented, can be traced to connect either to the East Anatolian fault zone or to the Dead Sea fault zone. One of these faults connects the Dead Sea fault zone to the east to the Amanos fault to the west. The Amanos fault, a N-trending normal fault, is a part of the East Anatolian fault zone since it is apparently a left-step fault between the main and southern strands of the East Anatolian fault zone. The Dead Sea fault zone also is connected to the East Anatolian fault zone northeast of the town of Narli and/or northeast of the Hazar lake. Therefore we suggest that the two fault zones can be considered as one broad fault system in southeastern Turkey, although they are well recognized as two different fault zones. This fault system is responsible for several complex Neogene structural features of the western part of the southeastern Turkey. One of these is the Hatay graben which can be divided into southern, central, and northern parts. The graben contains down to the west normal faults in its southern part. The central part of the graben is a divergent strike-slip basin and the northern part is a half-graben.
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That the East Anatolian fault is made up of discrete segments of different strike and diverse structural style is well illustrated by oblique hand-held photographs taken from the Space Shuttle. Linear and curvilinear faults plus major folds show the variable deformability of the collage of material that constitutes the Anatolian Plate, now undergoing the early stages of collision tectonics.
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Strike slip on various scales and on faults of diverse orientations is one of the most prominent modes of deformation in continental convergence zones. Extreme heterogeneity and low shear strength of continental rocks are responsible for creating complex 'escape routes' from nodes of constriction along irregular collision fronts toward free faces formed by subduction zones. The origin of this process is poorly understood. The 2 main models ascribe tectonic escape to buoyancy forces resulting from differences in crustal thickness generated by collision and to forces applied to the boundaries of the escaping wedges. Escape tectonics also creates a complicated geological signature, whose recognition in fossil examples may be difficult. We examine the Neogene to present tectonic escape-dominated evolution of Turkey both to test the models devised to account for tectonic escape and to develop criteria by which fossil escape systems may be recognized.-from Authors
The deep central segment of Death Valley, California, may be related to strike-slip faulting along the Death Valley fault zone. The trend of the fault zone along the central segment of Death Valley is slightly oblique to the fault trend elsewhere, and strike-slip movement may have caused a "pulling apart" of the two sides of the valley along this obliquely oriented segment of the fault.
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The Suşehri section of the North Anatolian Fault Zone (NAFZ) is dominated by an active fault-wedge basin. Its recent configuration is a Quaternary strike-slip depression superimposed on a larger, fault-controlled fluvial to lacustrine setting inherited from the Pliocene. In and around the Suşehri fault-wedge basin, the NAFZ is characterized by the North Anatolian master fault (NAMF) or principal displacement zone (PDZ) and four second-order fault sets, namely the Kelkit, Akçaaǧil, Beydeǧirmeni and Ekenek fault sets. The NAMF cuts through the basin. The fault sets border the margins of the basin and impart a double divergence character to the NAMF which is proposed as an evolutionary model for the Suşehri fault-wedge basin. The Suşehri basin fill deposits of Pliocene age rest on the quiet and shallow-marine limestones of Burdigalian age with a sharp angular unconformity. Besides, the upper half of the Pliocene basin fill deposits is dominated by the well-developed syndepositional mesofractures, which reveal the existence of a right-lateral shearing at the time of deposition. These observations also imply the emergence of a new tectonic regime after the Burdigalian by which time the Suşehri basin had experienced a subsidence of about 660 m to 1150 m during its evolution. On the other hand, at the south-easternmost end of the Suşehri basin, the Lutetian volcano-sedimentary sequence of the Yeşilyayla Group is cut and displaced right-laterally by about 35 km, which is the detectable minimum offset on the NAFZ.Finally, during the 1939/12/27 Erzincan earthquake, the Erzincan-Erbaa segment of the NAFZ was reactivated and several modern faults were produced. Along these modern faults some natural and man-made features were displaced right-laterally. These offsets vary in decreasing order from 7.5 m near the epicenter at the southeastern end to 3.7 m away from it at the northwestern end of the Erzincan-Erbaa segment of the NAFZ.
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According to the collected Data, two volcanic cycles were stipulated. The first cycle begins during Serravallian and consists of products with calc-alkaline affinity, among which high K-type prevails. It came to an end between 5 and 6 m. y. with largely extended ignimbrite covers. Following this, a second cycle characterised by mainly fissure lava flows with Na-alcaline affinity (ne-normative and hy-normative) took place and continued to recent times, assuming a central character during the Quaternary. In this period the emmitted magma shows beside the continuing alkaline activity a transitional character and tholeiitic affinity. Variations within the volcanological and mineralogical character were found to be consistent with the tectonic evolution of the area. This evolution is characterised by two main tectonic phases that developed during Eocene and at the limit between Miocene and Pliocene respectively. These two phases were found to match with the two main volcanic cycles. The important variations noticed in the evolution of both volcanism and coeval deformation can, however, be explained according to a Geodynamic cycle as resulting from the complex indentation mechanism of the Turkish-Iranian mass by the Arabian plate. Alkaline magma generation as well as the subalkalic and oversaturated character of Quaternary volcanics in the study area could be explained as a result of stress field variation together with a change of the physico-chemical conditions in the mantle. It is, however, concluded that rigid application of models on the nature and evolution of volcanism usually accepted for the lithosphere convergence areas, is largely unsatisfactory in this region.
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We show that the 33 km long Gölbaşi basin on the East Anatolian fault zone marks the triple junction between the African. Arabian, and Turkish plates. The main strand of the Turkish-Arabian plate boundary, the Göksu fault, enters this basin from the ENE before splaying to form faults which develop farther southwest into the Turkish-African and African-Arabian boundaries. The Gölbaşi-Türkoǧlu fault, the Turkish-African boundary, is shown to have slipped 16km: the prevously unrecognised Kirkpmar fault, the African-Arabian boundary, has slipped 17km. We propose that this fault geometry developed at c. 3 Ma following earlier slip, starting at c.5 Ma, on other strike-slip faults nearby which marked the start of westward motion of the Turkish plate.
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Seismological investigations in W Anatolia, NW Turkey have identified linear patterns of earthquake epicentres outlining a wedge-shaped block in the area of the Marmara Sea. This block shows different seismic characteristics from the rest of W Anatolia and appears to act as a separate tectonic unit. Earthquake fault-plane mechanisms show that the Marmara block is being rotated and sheared in order to accommodate the right-lateral motion of the North Anatolian Fault and the extensional tectonics of SW Anatolia. - from Authors
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The Big Pine left lateral fault extends northeastward from Big Pine Mountain to the right lateral San Andreas fault, while the left lateral Garlock fault extends northeast from the San Andreas, but from a point 5 miles to the southeast. The Big Pine fault is considered the western segment of the Garlock fault as offset by the San Andreas. Movement on this Garlock-Big Pine fault zone appears to have caused the anomalous east-west trend of the San Andreas fault in this vicinity. Tens of miles of lateral movement have probably occurred on these faults with the possibility of a cumulative movement on the San Andreas of hundreds of miles since Jurassic time. Such distances are important elements in reconstructing paleogeologic conditions. The three concurrently active, long, steep, and deep faults are considered major conjugate shears which define a primary strain pattern of relative east-west extension and north-south shortening of an area of approximately 120,000 square miles. A northeast-southwest counterclockwise compressive couple, possibly set up by drag due to the deep-seated movement of rock material from the Pacific region, is tentatively postulated as causing the deformation in this large region.
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Sandbox analogue models of pull-apart basins that developed in sedimentary strata above releasing steps in underlying basement faults are characterized by rhombic basins that are flat-bottomed box grabens with a subhorizontal synkinematic basin infill. Steep to nearly vertical, sigmoidal oblique-slip and segmented oblique-extensional faults are the dominant bounding structures of the pull-apart basins. Cross-basin, short-cut faults link the offset principal displacement zones that are characterized by flower structure development. The structural architectures of the physical models compare directly in form and dimensions to natural examples of strike-slip pull-apart basins.
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Pull-apart basins or rhomb grabens and horsts along major strike-slip fault systems in the world are generally associated with horizontal slip along faults. A simple model suggests that the width of the rhombs is controlled by the initial fault geometry, whereas the length increases with increasing fault displacement. We have tested this model by analyzing the shapes of 70 well-defined rhomb-like pull-apart basins and pressure ridges, ranging from tens of meters to tens of kilometers in length, associated with several major strike-slip faults in the western United States, Israel, Turkey, Iran, Guatemala, Venezuela, and New Zealand. In conflict with the model, we find that the length to width ratio of these basins is a constant value of approximately 3; these basins become wider as they grow longer with increasing fault offset. Two possible mechanisms responsible for the increase in width are suggested: (1) coalescence of neighboring rhomb grabens as each graben increases its length and (2) formation of fault strands parallel to the existing ones when large displacements need to be accommodated. The processes of formation and growth of new fault strands promote interaction among the new faults and between the new and preexisting faults on a larger scale. Increased displacement causes the width of the fault zone to increase resulting in wider pull-apart basins.
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We present and interpret Global Positioning System (GPS) measurements of crustal motions for the period 1988-1994 at 54 sites extending east-west from the Caucasus mountains of southern Russia, Georgia, and Armenia to the Aegean coast of Turkey and north-south from the southern edge of the Eurasian plate (Pontus block) to the northern edge of the Arabian platform. Viewed from a Eurasia-fixed reference frame, sites on the northern Arabian platform move N38+/-13°W at 20+/-3mm/yr, roughly consistent with the velocity implied by NUVEL 1A circuit closure (N23+/-7°W at 24+/-2mm/yr). The motion of Arabia appears to be transferred directly to the region of Turkey north of the suture. However, eastern Turkey is characterized by distributed deformation while central/western Turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the Anatolian plate. Internal deformation within the central part of the Anatolian plate is less than 2 mm/yr. The Anatolian plate is decoupled from Eurasia along the right-lateral, strike-slip North Anatolian fault (NAF). This different response in eastern and western Turkey to the collision of Arabia may result from the different boundary conditions, the Hellenic arc forming a ``free'' boundary to the west and the Asian continent and oceanic lithosphere of the Black and Caspian Seas forming a resistant boundary to the north and east. We derive a best fitting Euler vector for Anatolia-Eurasia motion of 29.2+/-0.8°N, 32.9+/-0.4°E, 1.3+/-0.1°/m.y. The mapped surface trace of the NAF corresponds well to a small circle about this pole. The new Euler vector implies an upper bound for NAF slip rate of 30 +/-2mm/yr (i.e., assuming all relative motion is accommodated along the NAF). Using the NUVEL 1A Euler vector for Arabia-Eurasia and the GPS Euler vector for Anatolia-Eurasia, we determine an Arabian-Anatolia Euler vector of 31+/-2°N, 45+/-2°E, 0.9+/-0.1°/m.y. and an upper bound on the East Anatolian fault slip rate of 15+/-3mm/yr. The Aegean Trough region of western Turkey deviates significantly from coherent plate rotation. In addition to rotating with Anatolia, this region shows roughly N-S extension at a rate of 14+/-5mm/yr. Taken together with satellite laser ranging results along the Hellenic arc, the contemporary pattern of deformation indicates increasing motions toward the arc, suggesting that the westward displacement and counterclockwise rotation of Anatolia is driven both by ``pushing'' from the Arabian plate and by ``pulling'' or basal drag associated with the foundering African plate along the Hellenic subduction zone.
Article
The Kazova basin is located within the Almus Fault Zone (AFZ), a splay fault system of the North Anatolian Fault Zone, in the central Pontides, Turkey. It is a 0.7–10-km-wide, 60-km-long, wedge-shaped right-lateral strike-slip depression bounded by the Mercimekdaǧi-Çamdere fault set in the north and the Tokat fault set in the south. The Kazova basin is superimposed on pre-Pliocene basement rocks while its basin fill comprises the Pliocene to lower Quaternary Kizkayasi and Çerçi formations, and Quaternary alluvials.The Mercimekdaǧi-Çamdere and Tokat fault sets of the AFZ, the basin-margin faults of the Kazova basin have a considerable amount of normal separation, and show a divergent character. Here, the Kazova basin is interpreted as an active negative flower structure, where the combination of normal movement (extension) along the different segments of the AFZ, and the oblique extension between its branching splays resulted from a natural response to the anticlockwise rotation along the AFZ are suggested basin-forming mechanism. This kind of basin is first from Turkey although different types of strike-slip basins, such as fault-wedge, pull-aparts, composite pull-aparts, are widely represented and well-known.
Article
The Karasu Rift (Antakya province, SE Turkey) has developed between east-dipping, NNE-striking faults of the Karasu fault zone, which define the western margin of the rift and west-dipping, N–S to N20°–30°E-striking faults of Dead Sea Transform fault zone (DST) in the central part and eastern margin of the rift. The strand of the Karasu fault zone that bounds the basin from west forms a linkage zone between the DST and the East Anatolian fault zone (EAFZ). The greater vertical offset on the western margin faults relative to the eastern ones indicates asymmetrical evolution of the rift as implied by the higher escarpments and accumulation of extensive, thick alluvial fans on the western margins of the rift. The thickness of the Quaternary sedimentary fill is more than 465 m, with clastic sediments intercalated with basaltic lavas. The Quaternary alkali basaltic volcanism accompanied fluvial to lacustrine sedimentation between 1.57 ± 0.08 and 0.05 ± 0.03 Ma. The faults are left-lateral oblique-slip faults as indicated by left-stepping faulting patterns, slip-lineation data and left-laterally offset lava flows and stream channels along the Karasu fault zone. At Hacılar village, an offset lava flow, dated to 0.08 ± 0.06 Ma, indicates a rate of left-lateral oblique slip of approximately 4.1 mm·year–1. Overall, the Karasu Rift is an asymmetrical transtensional basin, which has developed between seismically active splays of the left-lateral DST and the left-lateral oblique-slip Karasu fault zone during the neotectonic period.
Article
The convex-northwards arc of the North Anatolian fault zone between Çerkeş and Erbaa contains structures and landforms permitting right-lateral displacements for several time intervals to be estimated. Within the Pontus Formation (Late Miocene-Early Pleistocene) in basins along the fault zone, an unconformity, representing a time interval from the latest Tortonian to the earliest Pliocene, is interpreted as marking the transformation of the structure from a broad shear zone to a narrow fault belt. Although the amount of displacement during the shear zone phase is unknown the offset of a sedimentary facies boundary in the Lower Pontus Formation of the Havza-Ladik basin demonstrates that since the latest Tortonian there has been 25 km of right-lateral slip. The offset of valleys and ridges suggests that there has been 8 km of Quaternary displacement, about 2 km of it in the late Quaternary and at least 500 m during the Holocene. Structures in the Pontus Formation indicate that the early history of the western Neogene basins was influenced by regional compression and that the later histories of all basins were dominated by strike-slip displacements. The main active trace is discontinuous, the 2 km-wide belt containing subordinate en échelon faults whose geometry is consistent with development during right-lateral shear.
Article
Recent neotectonic studies, including remote-sensing, aerial photographs, geological field mapping on various scales and measured stratigraphic section substantiate the existence of a large sinistral intracontinental transcurrent structure, which we call the Central Anatolian Fault Zone (CAFZ). This is an approximately 730-km-long, 2-km- to 80-km-wide, NE-trending, active sinistral strike-slip fault zone that cuts across the Anatolian plateau between Düzyayla in the northeast and Anamur County in the southwest. It continues onward beneath the Eastern Mediterranean Sea and determines the boundary of the Antalya and Adana basins as far as to the west of Cyprus. The CAFZ is a very young neotectonic structure. It resulted from the reactivation and propagation of an older paleotectonic structure, the so-called ‘Ecemi Corridor’, in both NNE and SW directions across the Inner Tauride Suture in the Plio-Quaternary times. Based on geometric discontinuities, the CAFZ is divided into 24 segments. Each of them is characterized by a number of strike-slip morphotectonic features reflecting recent motions. The easternmost part of the Anatolian Platelet is being deformed internally by several dextral to sinistral intraplate strike-slip faults. These are the Lake Salt Fault Zone (LSFZ), the Salanda Fault (SF), the CAFZ, the Göksu-Yazyurdu Fault Zone (GYFZ) and the Malatya-Ovacik Fault Zone (MOFZ). They take up lesser motion and are younger than boundary faults of the Anatolian Platelet. The GYFZ and MOFZ splay from the NATF, cut across the Anatolian Platelet and then meet to the EATF. Whereas, other faults are confined into the Anatolian Platelet and seem to be independent structures. However, present-day structural pattern of all these intraplate faults and boundary faults of the Anatolian Platelet indicates a regional strain pattern of NNW-SSE-directed shortening and ENE-WSW-directed extension, and they seem to have developed to accommodate northward motion of the Arabian Plate since late Early Pliocene times.
Article
The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the apparently little-deforming interior of central Turkey. The direction of overall slip across this zone is crucial to the determination of the slip rate on the North Anatolian Fault. We use long-period P- and SH-waveforms to determine the source parameters of the four largest earthquakes that occurred in, or near, the East Anatolian Fault Zone in the last 35 years. Only one of these actually involved left-lateral strike–slip motion on a NE–SW fault. But the other three, and the nearby 1975 Lice earthquake, all had steeply dipping nodal planes with a NNW strike: if these were the auxiliary planes then all the earthquakes had a slip vector direction within about 10° of 063°. If this direction represents the Arabia–Turkey motion, then the slip rate on the North Anatolian Fault must be in the range 31 to 48 mm yr−1, with a probable value of 38 mm yr−1, and the overall slip rate across the East Anatolian Fault Zone must be about 29 mm yr−1 with a range of 25–35 mm yr−1.
Article
The east Anatolian plateau and the Lesser Caucasus are characterised and shaped by three major structures: (1) NW- and NE-trending dextral to sinistral active strike-slip faults, (2) N-S to NNW-trending fissures and /or Plio-Quatemary volcanoes, and (3) a 5-km thick, undeformed Plio-Quatemary continental volcanosedimentary sequence accumulated in various strike-slip basins. In contrast to the situation in the east Anatolian plateau and the Lesser Caucasus, the Transcaucasus and the Great Caucasus are characterised by WNW-trending active thrust to reverse faults, folds, and 6-km thick, undeformed (except for the fault-bounded basin margins) continuous Oligocene-Quaternary molassic sequence accumulated in actively developing ramp basins. Hence, the neotectonic regime in the Great Caucasus and the Transcaucasus is compressional-contractional, and Oligocene-Quaternary in age; whereas it is compressional-extensional, and Plio-Quatemary in age in the east Anatolian plateau and the Lesser Caucasus.
Article
Lake Hazar lies within a small pull-apart basin along the East Anatolian Transform Fault in south-eastern Turkey. Deltas are formed where streams debouch into the low-energy lacustrine environment. The facies constituting the deltas include delta plain debris flow, braided stream, and marginal lacustrine deposits; delta front foreset and mouth bar deposits; prodelta and lacustrine deposits. The facies are spatially restricted with sharp transitions. Facies sequences and relationships indicate two distinct styles of deltaic sedimentation. Fan deltas with a tripartite structure characteristic of Gilbert-type deltas comprise the marginal drainage system and form along the basin margins. Mouth bar deltas develop where the axial drainage system of the basin debouches into the lake. The distribution of the two deltaic types is thought to be a function of gradient and controlled by position relative to faults within the basin.
Article
Trench investigations along the Bree fault scarp in Belgium, in the framework of a first paleoseismological experience in the area of the Lower Rhine Graben system, have not only demonstrated the existence of seismogenic faults almost extending to the present ground surface, but also exposed several types of soft-sediment deformation affecting sandy sediments and soils of inferred late Weichselian to Holocene age. The observed features include asymmetric folding, small-scale normal faulting, possible sand intrusions, and small water escape or load structures. Establishing a seismic origin for the individual features is not always possible based on their sedimentary characteristics only, particularly due to the potential confusion with periglacial phenomena, but their abundance, the close association of different deformational styles, and their vicinity to a known active fault, all seem to be compatible with an earthquake-induced scenario. The features are to some extent comparable to those generated during the recent MS 5.3 Roermond earthquake at the opposite side of the Roer Valley Graben. Stratigraphical and mutual geometrical relationships suggest the occurrence of at least three distinct deformational events since probably 30,000 years, and one event before that time. Since nothing is yet known about their regional distribution, however, estimating the associated paleomagnitudes from these soft-sediment deformations is premature.
Article
Pull-apart basins are structural depressions formed by localized extension along strike-slip fault systems, typically at releasing bends or steps in the fundamental strike-slip system. Analog modeling is used to evaluate the sequence of structural evolution of pull-apart basins and factors that control their degree of structural asymmetry and geometry. Basin evolution, internal structure and overall symmetry are investigated for oblique releasing step angles and with varying rates of displacement between brittle and ductile crust on opposing sides of the strike-slip system, while maintaining relative rates between brittle crust on opposing sides of the basin. Pull-apart basin evolution is separated into three stages: incipient, early, and mature. Incipient pull-apart basins are characterized by formation of a normal-fault bounded graben or half-graben parallel to the oblique step between main strike-slip zones. In the early stage of formation, additional normal faults form toward the basin interior from the original bounding faults, and cross-basin strike-slip faults cut diagonally across the basin interior; basin-bounding normal fault systems are characterized by lateral variations of fault throw and localized relay ramps. In the mature stage of evolution, strike-slip and normal faults join to completely bound the pull-apart basin. Analog model results indicate that displacement associated with cross-basin faults causes development of a through-going strike-slip fault that links the two main strike-slip displacement zones, ultimately resulting in a decline in normal fault activity. Asymmetric, symmetric, and hybrid pull-apart basins all follow the same overall deformation sequence just described. The asymmetry of a pull-apart basin is controlled by the degree of decoupling between brittle and ductile crust beneath the two crustal blocks in relative motion. This is modeled by maintaining a constant relative rate of motion between opposing fault blocks in all models, but varying the rate between the blocks and the fixed (model) basement (‘absolute’ rate). Models in which one side of the detachment is fixed with respect to the basement form asymmetric pull-apart basins defined by a half-graben with the master fault on the mobile side. In models where opposing sides of the fault system are equally decoupled from the basement, symmetrical pull-apart basins form, defined by horst and graben structures and master fault dominance switching sides along the length of the basin. Fault segmentation associated with relatively immature pull-apart basins may be capable of arresting earthquake rupture. Late linkage of main strike-slip zones by a cross-basin fault could extend potential rupture area, dramatically increasing the possibility for large-magnitude earthquakes.
Article
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≈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.
Article
The tectonic setting for the area around the Arabia-Africa-Anatolia triple junction is described from combined Landsat-SPOT satellite image analysis and field observations. Since the Late Miocene the motion along the East Anatolian Fault generated major structures corresponding to shortening with a sinistral-slip component. The 150 km wide area of the triple junction is highly deformed by folding and thrusting, distributed mainly on the border of the Anatolian block. In addition, kinematic reconstructions confirm that the Arabia-Anatolia relative motion is both sinistral and convergent. The sinistral strike-slip faults of the East Anatolian Fault zone are of second-order and local consequences of the N-S Arabia-Anatolia collision.
Article
Several areas along the Boconó fault zone are characterized by elongate, almond-shaped basins containing thick alluvial sequences, mainly of Quaternary age, and bounded by faults with normal Quaternary displacements. These areas are separated by segments characterized by narrow fault traces and right-lateral displacements. The fault-bounded basins are interpreted as pull-apart basins that originated at releasing bends along the fault zone. The size of the La González pull-apart basin suggests that Pliocene (?)-Quaternary right-lateral slip on the Boconó fault zone was of the order of 7–9 km.