Browsing by Author "Selcuk, Azad Saglam"

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Earthquake Induced Sedimentary Structures (Seismites): Geoconservation and Promotion as Geological Heritage (Lake Van-Turkey)
(Springer Heidelberg, 2017) Uner, Serkan; Aliriz, Merve Gizem; Ozsayin, Erman; Selcuk, Azad Saglam; Karabiyikoglu, Mustafa
The Lake Van Basin, located at the collision zone of the Eurasian and Arabian plates, has great potential in terms of geological heritage. The world's largest soda lake which gives its name to the basin contains magnificent geological structures. Lacustrine deposits of the lake represent important clues about seismic activity during the Late Quaternary in addition to its sedimentological and paleontological background. Seismites-deformational structures which are formed during earthquakes in unconsolidated sediments-are very rare geologic phenomena. These structures, formed by earthquakes of magnitude >= 5 under suitable conditions, provide valuable information about the responsible faults and their seismic repetition frequency for the region. Today, rising awareness of geological heritage is a glimmer of hope for the protection and preservation of these rare structures in the Lake Van Basin for the generations to come. Conservation of these structures will also help the protection of other naturally, historically, and culturally significant geological beauties. The responsibility for the promotion and conservation of these geological heritages should be a mission not only for the hosting country but also for the entire geological community.
Evaluation of the Plio-Quaternary Tectonic Stress Regime From Fault Kinematic Analysis in the Lake Van Basin (Eastern Anatolia)
(Pergamon-elsevier Science Ltd, 2020) Selcuk, Azad Saglam; Erturac, Mehmet Korhan; Sunal, Gursel; Cakir, Ziyadin
We focus on the Neogene-Quaternary tectonic evolution of the Lake Van Basin located within the Turkish-Iranian Plateau. To better understand the complex tectonic history of the region and determine the paleostress patterns, we investigate and report on the geometric, structural, and kinematic characteristics of the Basin based on field observations of fault-slip orientations which are classified according to radiometric ages of the basin stratigraphy. The analysis of large-scale structures and fault kinematics indicate that three different deformation phases prevailed in the Lake Van Basin during the Neogene-Quaternary periods. Phase 1 is characterized by NW-SE extension and NE-SW contraction that gave rise to the development of strike-slip faults with thrust or normal components during the late Miocene, deforming the fluvial sediments which expose at east/northeast of the Basin. Phase 2 is characterized in fluvial and lake deposits of the Middle Pleistocene, deformed by dominant contraction stress regime effective along NW-SE direction. The late Pleistocene tectonic regime (Phase 3) consists of transpressional deformation that develops under NNW-SSE compression and ENE-WSW extension. According to our analysis, the present-day deformation pattern of the Lake Van Basin is dominated by compression at east, while at the northern part is transtensional.
Evaluation of the Relative Tectonic Activity in the Eastern Lake Van Basin, East Turkey
(Elsevier, 2016) Selcuk, Azad Saglam
The eastern part of the Lake Van basin (Van region, Turkey) is controlled by reverse faults, such as the Gurpinar, Everek and Alakoy faults. These represent the major tectonic structures within the Van region and have caused many devastating earthquakes. Based on quantitative analyses, the Quaternary activity and topographic relief control of each of these faults was investigated. The Gurpinar, Everek and Alakoy faults are restricted to the southern slopes of the Guzelsu, Everek, and Karasu basins, respectively. Analyses of the mountain front sinuosity (S-mf) and valley floor width-to-height ratio (V-f) suggest high activity along the Gurpinar fault, the Everek fault, and the western part of the Alakoy fault. Furthermore, based on the integration between S-mf and V-f, the estimated uplift rates were observed to increase from north to south. The Gurpinar and Everek hanging-wall blocks are characterized by uplift rates of >0.5 mm yr(-1), whereas the Alakoy fault exhibited a rate of 0.05 to 0.5 mm yr(-1). These faults produce knickpoints or knickzones, complex basin hypsometric curves, and high values of the stream length-gradient index. Based on these geomorphic analyses, it was established that the tectonic activity of both the Gurpinar and Everek faults is greater than that of the Alakoy fault. (C) 2016 Published by Elsevier B.V.
Evolution of Camlik Fissure-Ridge Travertines in the Baskale Basin (Van, Eastern Anatolia)
(Taylor & Francis Ltd, 2017) Selcuk, Azad Saglam; Erturac, M. Korhan; Uner, Serkan; Ozsayin, Erman; Pons-Branchu, Edwige
Fissure-ridge travertines (FRTs) are of great importance for the determination and comparison of tectonic deformation in a region. The coeval development of these travertines with active fault zones supplies significant information about regional dynamics in terms of deformation pattern and evolution. In this paper, the characteristics of FRTs of the Baskale basin (eastern Turkey) and responsible regional tectonism are discussed for the first time. The Baskale basin is located between the Baskale Fault Zone (BFZ) characterised by Camlik fault and Isikli-Ziranis fault. It is located between dextral Yuksekova Fault Zone and southern end of dextral Guilato-Siahcheshmeh-Khoy Fault system (Iran). Various morphological features indicating recent activity are exposed along the BFZ, including offsetting rivers, fissure-ridge travertine and fault scarps. The Camlik fissure-ridge travertine composing of three different depositions is observed along the eastern edge of the BFZ with approximately parallel orientations. The Famlik fissure-ridge travertine has been formed and developed on fault zone related to strike-slip or oblique movements. We explain how kinematic changes of faults can influence the fissure-ridge development.
Frs (Fault Rating System): a Quantitative Classification of Active Faults for Hazard Evaluations
(Springer, 2024) Selcuk, Levent; Selcuk, Azad Saglam
The correct estimation of seismic hazards is a touchstone of seismic risk assessments. However, there is no quantitative or standard methodology to include the impacts of geological (i.e., seismo-tectonic) features of active faults or fault zones, and current classification schemes are not useful in hazard evaluations. Therefore, an attempt has been made to develop a methodology that integrates seismo-tectonic parameters of active faults to better inform urban and regional planning decisions. Fault rating system (FRS) provides a comparative review of faults/fault zones using a rating-based approach. In this approach, seven seismo-tectonic parameters are used to classify the fault/fault zone. Each of the seven parameters is assigned a value corresponding to the seismo-tectonic characteristics. The sum of the seven seismo-tectonic parameters is the fault index (FI) value, which lies in the range 0-100. A total of 64 important faults/fault zones were statistically analyzed to determine the best correlations with FI and moment magnitude (Mw) and peak ground acceleration (PGA). It was found that the FI values provide strong correlations with maximum Mw and PGA. It is proposed urban and regional planners use FRS to ensure a consistent approach in characterizing key aspects of active faults in earthquake-prone regions and in estimating ground motion parameters.
Geology of the Caldiran Fault, Eastern Turkey: Age, Slip Rate and Implications on the Characteristic Slip Behaviour
(Elsevier, 2016) Selcuk, Azad Saglam; Erturac, M. Korhan; Nomade, Sebastien
The Caldiran Fault is a strike slip fault with a dextral slip in East Anatolia. The activity on this fault was marked by the November, 241976 earthquake (Mw: 7.1) which produced an similar to 50 km long surface rupture and caused 3840 fatalities, which was close to half of the population living along the fault at that time. Together with the North Tabriz Fault in Iran, it is regarded as the southern boundary of the Caucasus Block. The fault has an average annual slip rate of 8.1 from 10.8 mm yr(-1), as derived from elastic block modelling. We present results from a detailed morphotectonic survey along the fault. The Caldiran Fault is comprised of three segments, each of which is eparated by bend structures that bend towards the SW with a total change in strike of 20 degrees from east to west. The offsets of lithological contact markers show that the long-term geological slip rate for the Caldiran fault is approximately 3.27 +/- 0.17 mm yr(-1) for a duration of approximately 290 ka. The cumulative offset of the fault was determined from an analysis of a dome-shaped rhyolitic volcano which constrained the age of the fault to the Middle-Late Pleistocene. An analysis of small-scale morphological offset markers indicates a characteristic slip behaviour of the Caldiran Fault for the last 3 events with an average offset of 2.6 m. (C) 2016 Elsevier B.V. All rights reserved.
Long-Term Slip Rate Estimation for Ercis Fault in East Anatolian Compressive Tectonic Block From Geologic and Geomorphologic Field Evidence
(Wiley, 2021) Selcuk, Azad Saglam; Kul, Ahmet Ozkan
The Ercis Fault, which bounds the northern part of the Lake Van Basin, is approximately 50 km long with right-lateral strike-slip movement in a N30-50 degrees W direction. The Ercis Fault starts in the northwest, south of Girekol Volcano, and extends to the Turkey-Iran border, and together with the caldiran Fault forms the tectonic boundary between the Turkey-Iran Block and Lesser Caucasus-Talesh Block. Offset riverbeds, fault-controlled drainage systems, deformed alluvial fans along the faults, Plio-Quaternary volcanics, and volcanic structures are geomorphic and tectonic features that show that the Ercis Fault is active in the region. This fault has played an active role in the deformation of the Eastern Anatolian Plateau, which developed as a result of collision of the Arabian and Eurasian plates. In this study, the role of the Ercis Fault in the tectonic evolution of the region was investigated using geologic, geomorphologic, and remote sensing analysis methods. According to the morphometric indices used in the study, values of 1 < Smf < 2.1, 0.2 < Vf < 3.29, 0.3 < HI < 0.5, 25 < SL < 850 and 100 < Ksn < 600 were obtained. Results show that the area has an extremely young topography and is actively uplifting. It has been determined that the uplift rate in the region has increased in the northwest and south-east compared to other areas and is more than 0.5 mm yr(-1). According to the remote sensing and field studies, an approximately 850 m right-lateral offset is observed in the Delicay River, which is cut by the Ercis Fault, and that the long-term slip rate of the Ercis Fault is 2.02 +/- 0.12 mm yr(-1).
Neotectonic and Topographic Evolution of the Bitlis-Zagros Fold-Thrust Belt, Se Turkey Br
(Tubitak Scientific & Technological Research Council Turkey, 2023) Zorer, Halil; Ozturk, Yahya; Selcuk, Azad Saglam
The Bitlis-Zagros Fold-Thrust Belt is one of the world's largest deformation zones, extending from the Eastern Mediterranean in southern Turkey to in the south of Iran. This deformation zone is partitioned between different structures; however, little is known about the relative activities of these different structures and their effects on topography. An area located in the northern part of Bitlis- Zagros Fold-Thrust Belt, Just south of the Eastern Anatolian Plateau was studied in detail to analyze the effect of active tectonism on topographic development. The effects of active deformation structures such as Hakkari and Sirvan Fault Segments on the topographic evolution of Kato Folds and Sinebel Valley were investigated to understand the fold and thrust fault activity. Geomorphic Indices were used, such as HC, HI, SR, Ksn together with rose analysis based on bedding measurements. Investigation of folding in the region Indi- cates the effective stress regime in the precolliston zone was in NW-SE compression direction. The deformation structures, effective in the postcollision zone developed due to N-S directional compression, and are shown here to have different effects on topography of the region. This study has shown the relative uplift rate is highest in the areas where Hakkart and Sirvan Segments are pure thrust faults (0.4 mm year'), and lower in the transfer zone (0.2 to 0.4 mm year (1)) between the segments. As a result of this study. It is concluded that the main deformation structures controlling the topography in the region are not only thrust faults, but also structures that develop in the area of transfer zone.
Neotectonic Characteristics of the Inonu-Eskisehir Fault System in the Kaymaz (Eskisehir) Region: Influence on the Development of the Mahmudiye-Cifteler Basin
(Tubitak Scientific & Technological Research Council Turkey, 2012) Selcuk, Azad Saglam; Gokten, Yasar Ergun
The Inonu-Eskisehir Fault System (IEFS) is a NW- to WNW-trending zone of active deformation about 15-25 km wide, 400 km long and characterized predominatly by strike-slip faulting. In this study, the Yorukkaracaoren (SE of Eskisehir)-Sivrihisar section of the IEFS was investigated. The system consists of three fault zones, namely the Alpu Fault Zone (AFZ), the Eskisehir Fault Zone (EFZ) and the Orhaniye Fault Zone (OFZ) in the study area. The EFZ is made up mostly of N30 degrees W-trending right-lateral strike-slip fault segments with normal components. However, the AFZ and OFZ are composed of E-W-trending normal and NE- to NW-trending strike-slip fault segments. The Mahmudiye-Cifteler-Emirdag basin is one of several strike-slip pull-apart basins along the Inonu-Eskisehir Fault System. It is an actively-subsiding NW-trending depression about 25 km wide, 85 km long located between Yortikkaracaoren and Emirdag. It contains two infills. The older and deformed (tilted and folded) mull, which rests with angular unconformity on the erosional surfaces of pre-Miocene metamorphic and non-metamorphic rocks, consists predominatly of lacustrine carbonates. The younger and undeformed basin infill (neotectonic mull) is composed of upper Pliocene-Holocene terrace deposits, alternations of sandstones, lacustrine mudstone to thin limestones and alluvial fans. The two basin infills separated by an angular unconformity, the deformation pattern of the older basin infill and the active bounding strike-slip faults all indicate the superimposed character of the Mahmudiye-cifteler-Emirdag pull-apart basin.
Non-Seismic Soft-Sediment Deformation Structures From Late Pleistocene Lacustrine Deposits of Lake Van (Eastern Turkey): Storm and Overloading Effect
(Elsevier Sci Ltd, 2019) Uner, Serkan; Selcuk, Azad Saglam; Ozsayin, Erman
Soft-sediment deformation structures of different types and sizes are frequently observed in the lacustrine deposits of Lake Van. According to sedimentary features and regional factors, these structures are categorized as non-seismic originated and seismically-induced, soft-sediment deformation structures. Well-preserved non-seismic originated, soft-sediment deformation structures were observed in fine-grained sandy and silty deposits at three locations (Catakdibi, Yumrutepe, and Yukanisikli), and occur at different stratigraphic horizons, exhibiting morphological variability as they consist of load, flame, and slump structures. The formation mechanisms of these structures are determined by the characteristics of their sedimentary facies and environmental conditions. Overloading, caused by rapid coarse sediment deposition or underwater landslides, and storm waves are identified as triggering mechanisms, while rapid sediment accumulation and underwater mass movements caused by volcanogenic shakes are the conditions responsible for the formation of non-seismic soft-sediment deformation structures, in terms of regional geodynamics. (C) 2019 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.
Probabilistic Seismic Hazard Assessment for Lake Van Basin, Turkey
(Springer, 2010) Selcuk, Levent; Selcuk, Azad Saglam; Beyaz, Turgay
The seismic hazard for the Lake Van basin is computed using a probabilistic approach, along with the earthquake data from 1907 to present. The spatial distribution of seismic events between the longitudes of 41-45A degrees and the latitudes of 37.5-40A degrees, which encompasses the region, indicates distinct seismic zones. The positions of these zones are well aligned with the known tectonic features such as the Tutak-CaldA +/- ran fault zone, the A-zalp fault zone, the GevaAY fault zone, the Bitlis fault zone and KarlA +/- ova junction where the North Anatolian fault zone and East Anatolian fault zone meet. These faults are known to have generated major earthquakes which strongly affected cities and towns such as Van, MuAY, Bitlis, A-zalp, Muradiye, CaldA +/- ran, ErciAY, Adilcevaz, Ahlat, Tatvan, GevaAY and GurpA +/- nar. The recurrence intervals of M (s) a parts per thousand yen 4 earthquakes were evaluated in order to obtain the parameters of the Gutenberg-Richter measurements for seismic zones. More importantly, iso-acceleration maps of the basin were produced with a grid interval of 0.05 degrees. These maps are developed for 100- and 475- year return periods, utilizing the domestic attenuation relationships. A computer program called Sistehan II was utilized to generate these maps.
Seismites as an Indicator for Determination of Earthquake Recurrence Interval: a Case Study From Ercis Fault (Eastern Anatolia-Turkey)
(Elsevier, 2019) Uner, Serkan; Ozsayin, Erman; Selcuk, Azad Saglam
The southern part of the Eastern Anatolian Plateau is a key region for understanding the tectonic activity and related deformation patterns of the Arabian-Eurasian collision zone. The geological record of seismic events collected from lacustrine deposits of Lake Van Basin is a critical requirement for seismic hazard assessment and seismic risk reduction. Our paleoseismic investigations revealed well-preserved seismites at five locations in late Pleistocene lacustrine deposits. The seismites were dated using an optically stimulated luminescence dating method and were arranged according to their ages. Their type, such as convolute, dish-and-pillar, flame, and ball-and-pillow structures, as well as their locations, ages, and stratigraphic distribution enable us to identify the responsible fault and the earthquake recurrence interval. On the basis of these properties, the Ercil Fault has been recognized as the structure responsible for creating the seismites. The time span between the seismites indicates an apparent earthquake recurrence interval of 125-250 years for large earthquakes (M >= 5) related to the Ercis Fault. The method applied here enriches our knowledge on the seismic hazards present in the northern Lake Van region.
Tectonic Controls on the Karliova Triple Junction (Turkey): Implications for Tectonic Inversion and the Initiation of Volcanism
(Elsevier, 2017) Karaoglu, Ozgur; Selcuk, Azad Saglam; Gudmundsson, Agust
Few places on Earth are tectonically as active as the Karhova region of eastern Turkey which comprises a triple junction (KTJ). Triple junctions result in complex kinematic and mechanical interactions within -the lithosphere generating tectonic inversions and uplift, extensive seismicity and volcanism. Here we present new data, and summarize existing data, on the tectonic evolution of the KTJ in eastern Turkey over the past 6 Ma. In particular, we present a kinematic model for the ICI) and the surrounding area as well as new structural maps. The deformation or strain rate has varied over this 6 million year period. The maximum strain rate occurred between 6 Ma and 3 Ma, a period that coincides with the initiation of activity in Varto Volcano.We suggest that increased strain rate and the initiation of activity at the Varto Volcano may be tectonically related. Subsequent to its formation, the Varto Volcano was dissected by active faults associated with the Varto Fault Zone, including reverse, normal and strike -slip faults. During thepast 3 Ma, however, the KTJ area was deformed, dominantly through dextral crustal movements associated to right -lateral faults. This deformation resulted in the development of a NE SW -trending extensional/transtensional regime, together with a complementary NW -SE -trending contractional regime. In the past 6 Ma the east end of the KTJ has been subjected to incremental deformation. This deformation has resulted in many episodes of faulting during (i) ongoing shortening phases driven by a regional -scale thrust tectonic regime, and (ii) local -scale transtensional phases caused by westward extrusion. (C) 2016 Elsevier B.V. All rights reserved.
Tectonic Geomorphology of Bozdo?an and Karacasu Grabens, Western Anatolia
(Univ Barcelona, 2023) Ozsayin, Erman; Dirik, Kadir; Ocakoglu, Faruk; Cartigny, Sanem Acikalin; Selcuk, Azad Saglam
Western Anatolia is one of the most rapidly extending and seismically active regions in the world. The circa N-S extension since the Early Miocene caused the formation of E-W trending major grabens and intervening horsts, having earthquake potentials with magnitude >= 5. The E-W oriented Buyuk Menderes Graben cross-cuts the broadly N-S oriented Bozdogan and Karacasu grabens, of which the boundary faults of the latter are the source of seismic activity. Geomorphic indices, including drainage basin asymmetry, mountain front sinuosity, valley-floor width to valley height ratio, stream length-gradient index and normalized channel steepness index, were used to evaluate the boundary fault segments of the Bozdogan and Karacasu grabens. The results indicate that both grabens are tectonically active and therefore regions of earthquake potential, consistent with the epicenters of earthquakes. Thus, it can be inferred that fault segments of second-order grabens, which are crosscut by the boundary faults of seismically active main depressions, are apparently reactivated by ongoing tectonism and may represent seismic activity. This suggestion applies also for similar basins located in the western Anatolia.