Turkish Journal of Earth Sciences 

About: Turkish Journal of Earth Sciences is an academic journal published by Scientific and Technological Research Council of Turkey. The journal publishes majorly in the area(s): Geology & Fault (geology). It has an ISSN identifier of 1300-0985. Over the lifetime, 742 publications have been published receiving 13386 citations.

The Karakaya Complex: A Review of Data and Concepts

Abstract: The Karakaya Complex in the Pontides consists of highly deformed and partly metamorphosed clastic and volcanic series of Permian and Triassic age. It is generally subdivided into two parts: The structurally lower part, called the Lower Karakaya Complex, consists of a mafic lava-mafic pyroclastite-shale-limestone succession metamorphosed in the greenschist and blueschist facies during the Late Palaeozoic or Triassic. The structurally upper part is made up of highly deformed Permian and Triassic clastic, volcaniclastic and volcanic rocks with exotic limestone blocks. There are currently two different models for the depositional setting and tectonic evolution of the Karakaya Complex. The rift model assumes that the Karakaya Complex was formed in a Late Permian rift, which developed into a marginal oceanic basin and closed by the latest Triassic. The subduction-accretion model regards the Karakaya Complex as subduction-accretion units of the Palaeo-Tethys.

Geology of the Caucasus: A Review

Abstract: Th e structure and geological history of the Caucasus are largely determined by its position between the still- converging Eurasian and Africa-Arabian lithospheric plates, within a wide zone of continental collision. During the Late Proterozoic-Early Cenozoic, the region belonged to the Tethys Ocean and its Eurasian and Africa-Arabian margins where there existed a system of island arcs, intra-arc rift s, back-arc basins characteristic of the pre-collisional stage of its evolution of the region. Th e region, along with other fragments that are now exposed in the Upper Precambrian- Cambrian crystalline basement of the Alpine orogenic belt, was separated from western Gondwana during the Early Palaeozoic as a result of back-arc rift ing above a south-dipping subduction zone. Continued rift ing and seafl oor spreading produced the Palaeotethys Ocean in the wake of northward migrating peri-Gondwanan terranes. Th e displacement of the Caucasian and other peri-Gondwanan terranes to the southern margin of Eurasia was completed by ~350 Ma. Widespread emplacement of microcline granite plutons along the active continental margin of southern Eurasia during 330-280 Ma occurred above a north-dipping Palaeotethyan subduction zone. However, Variscan and Eo-Cimmerian-Early Alpine events did not lead to the complete closing of the Palaeozoic Ocean. Th

The earthquake catalogues for Turkey

Abstract: The earthquake data from instrumental records in the last 40 years indicate the general seismicity of the earth. However, examining historical records is necessary to understand long-term seismicity. Catalogue studies about historical earthquakes in Turkey are limited. All these catalogues are on printed paper and a digital database has not yet been prepared. On the other hand, there is no common database for the focal mechanism solutions of the recent destructive earthquakes (Mw>=5.5) in the region. The present study aims to prepare two new digital databases for earth scientists so that the earthquake parameters can be reached from a single source. The first one is `The Historical Earthquake Catalogue of Turkey´ which includes parameters of the earthquakes occurring between 2100 B.C. and 1963 A.D. This database contains approximately 2285 events and is presented as an electronic supplement. The second dataset, `The Focal Mechanism Solutions Catalogue of Turkey´, contains fault plane solution parameters of the destructive earthquakes occurring between 1938 and 2004. All available mechanism solutions of the destructive earthquakes were collected, although the global moment tensor solutions reported via the internet were not included in the present study.

Extensional Neotectonic Regime through the NE Edge of the Outer Isparta Angle, SW Turkey: New Field and Seismic Data

Abstract: The Akflehir-Afyon Graben (AAG) is a 4—20-km-wide, 130-km-long NW—trending depression that separates central Anatolia in the NE and the Isparta Angle (IA) in the SW. Its southwestern margin-bounding fault determines the northeast edge of the outer IA that was previously interpreted as a compressional neotectonic structure, whereas our field evidence and recent seismic data substantiated that it is an oblique-slip normal fault characterising an extensional neotectonic regime. The AAG has an episodic and asymmetrical evolutionary history. This is indicated by two superimposed graben infills and structures. The older infill is folded, thrust-faulted and Early-early Middle Miocene in age. The younger infill is undeformed (nearly horizontal), Plio-Quaternary in age, and overlies the older infill with angular unconformity. Total throw amounts accumulated on both SW and NE margin-bounding faults, namely the Akflehir Master Fault (AMF) and the Karagoztepe Master Fault (KMF) since the Late Pliocene and Early Pleistocene, are 870 m and 200 m, respectively. Assuming a uniform motion, these values indicate motion rates of 0.3 mm/yr and 0.2 mm/yr, respectively, and the asymmetrical nature of the AAG. Kinematic analysis of surface slip data of both the AMF and KMF showed an oblique-slip motion with a minor right-lateral strike-slip component, and a NE—SW- directed extension. They also fit well with results of focal mechanism solutions of two recent seismic events, namely the 2000 December 15 Sultanda¤› (Mw=6.0) and the 2002 February 3 Cay (Mw=6.5) earthquakes. They have been sourced from the reactivation of the Akflehir-P›narkaya and Sultanda¤›-Maltepe sections of the AMF. The Cay earthquake caused devastating damage to structures and loss of life in the region. The Cay earthquake has also led to the development of ground ruptures and surface deformation. The geometry of the ground ruptures and focal mechanism solutions of both earthquakes proved once more that the southern margin-bounding fault of the AAG or the northeastern edge of the IA is an oblique-slip normal fault. Consequently, all of these field and seismic data reveal an extensional neotectonic regime through the northeast edge of the outer IA despite the previously reported compressional neotectonic regime. Isparta Ac›s›'n›n (GB Turkiye) KD D›fl Kenar›nda Genifllemeli Yenitektonik Rejim: Yeni Arazi ve Sismik Veriler Ozet: Akflehir-Afyon Grabeni (AAG) 4—20 km genifllikte, 130 km uzunlukta ve KB gidiflli, aktif bir cokuntu alan› olup, KD da yer alan orta Anadolu ve GB da yer alan Isparta Ac›s›'n› (IA) birbirinden ay›r›r. AAG'nin GB kenar›n› ve IA'n›n KD kenar›n› s›n›rlayan fay, daha once, s›k›flma turu bir yap› olarak yorumlanm›flt›r. Halbuki bizim arazi verilerimiz ve yeni sismik veriler, bu fay›n, genifllemeli yenitektonik rejimi karakterize eden verev at›ml› normal bir fay olduunu kan›tlam›flt›r. AAG aral›kl› (fas›lal›) ve bak›fl›ms›z bir geliflim tarihcesine sahiptir. Grabenin bu nitelii, ustuste gelmifl iki ayr› graben dolgusu ve grabenin kendine ozgu yap›s› ile belirginlik kazan›r. Daha yafll› olan graben dolgusu k›vr›ml› ve bindirme fayl› olup erken Orta Miyosen yafll›d›r. Daha genc olan graben dolgusu ise hemen hemen yatay konumlu olup s›k›flma turunde hic bir deformasyon gecirmemifltir. Pliyo-Kuvaterner yafll› olan graben dolgusu, daha yafll› olan graben dolgusu uzerinde ac›l› uyumsuzluk ile yer al›r. AAG'nin GB ve KD kenarlar›n› s›n›rlayan faylar (Akflehir ve Karagoztepe Ana Faylar›, AMF ve KMF) boyunca, Gec Pliyosen ve Erken Pliyostesen'den beri gercekleflmifl olan toplam dufley at›m miktarlar› s›rayla 870 m ve 200 m dir. Faylar uzerindeki devinimin tekduze olduu kabul edilirse, bu deerler, grabenin iki kenar› boyunca gercekleflen devinim h›z›n›n s›rayla 0.3 mm/y›l ve 0.2 mm/y›l olduunu ve AAG'nin bak›fl›ms›z niteliini ac›kca gosterir. Yuzeyde her iki ana fay (AMF ve KMF) duzleminden al›nan kayma verilerinin kinematik analizi, bu faylar uzerindeki devinimin, az miktarda sayanal dorultu bilefleni olan verev at›ml› bir devinim olduunu, ayr›ca genifllemenin de KD—GB dorultusunda gercekleflmekte olduunu gostermifltir. Arazi verileriyle elde edilen bu sonuc, 15 Aral›k 2000 Sultanda¤› (Mw=6.0) ve 3 fiubat 2002 Cay (Mw=6.5) depremlerinin odak mekanizmas›

Kinematics of the Middle East and Eastern Mediterranean Updated

Abstract: A revised quantitative, internally consistent, kinematic model has been determined for the present-day relative plate motions in the eastern Mediterranean and Middle Eastern regions, based on a combination of geological and GPS data. The relative motions of the brittle upper crust of the African and Arabian plates across the southern Dead Sea Fault Zone (DSFZ) are represented by relative rotation at 0.278i Ma -1 about an Euler pole at 31.1iN 26.7iE. The resulting predicted slip rate on the southern DSFZ is 4.0 mm a -1 . The kinematics of the northern DSFZ are described as relative rotation at 0.243i Ma -1 about the same Euler pole, the difference in rotation rates reflecting the absorption of a small component of the relative motion by distributed shortening in the Palmyra fold belt. The northern DSFZ, in Syria and southern Turkey, is regarded as a series of transpressional stepovers, along which the rate of left-lateral slip is substantially less than the rate of relative plate motion, because this slip is oriented strongly obliquely to the relative motion between the adjoining plates. This geometry seems to result in part from some strands of the northern DSFZ reactivating older fault segments, even though they were not optimally oriented relative to the plate motion, and in part because the ideal initial geometry of the DSFZ, which would have continued northwestward offshore of the Levant coastline towards Cyprus, was precluded by the high strength of the crust along this line. The revised slip rate on the East Anatolian Fault Zone (EAFZ) is estimated as ~8 mm a -1 . At this rate, restoring the observed slip requires the age of the EAFZ to be ~4 Ma. The previous phase of deformation, which involved slip on the Malatya-Ovac›k Fault Zone before the EAFZ came into being, is thus dated to ~7—4 Ma, suggesting a timing of initiation for the North Anatolian Fault Zone (NAFZ) of ~7 Ma, not ~5 Ma as has previously been thought. Local evidence from the western NAFZ also supports a ~7 Ma or Early Messinian age for the NAFZ. The overall present-day kinematics of the NAFZ are described using the Euler vector determined in 2000 using GPS: involving relative rotation between the Turkish and Eurasian plates at 1.2i Ma -1 about 30.7iN 32.6iE. This Euler vector predicts a rate of relative motion between these plates of ~25 mm a -1 , which when extrapolated overestimates the observed amount of localised right-lateral slip, suggesting the existence of a component of distributed right-lateral simple shear in the surroundings to the NAFZ as well. The predicted rate of left-lateral relative motion on the boundary between the Turkish and African plates is estimated as ~8 mm a -1 . However, the rate of localised left-lateral slip on the onshore part of this boundary is estimated as only ~2 mm a -1 , on the Yakap›nar-Goksun Fault: the difference being taken up by distributed deformation within the northern "promontory" of the African plate, which appears to involve a combination of anticlockwise rotation and distributed left-lateral simple shear. It is proposed that this boundary first developed at the same time as the NAFZ, but its original geometry involving left-lateral slip on the Karatafl-Osmaniye Fault has since become locked by the presence of relatively strong ophiolitic crust within this fault zone. The kinematic consistency of this model requires one to relax the assumption that brittle upper crust and mantle lithosphere are moving in step, consistent with the assumed presence of a weak layer of lower crust in between. The development of the NAFZ during the Messinian can thus be explained as a consequence of a combination of forces resulting from (a) shear tractions applied to the brittle upper crust of Turkey as a result of relative westward motion of mantle lithosphere, caused by the pre-existing relative motions between the African and Arabian plates during the earlier Miocene; and (b) the reduction in normal stress and increase in right-lateral shear stress that resulted from the dramatic water unloading during the Messinian desiccation of the Mediterranean basin. Analysis indicates that this mechanism requires the effective viscosity of the lower crust of Turkey to be ~5-3x10 19 Pa s, consistent with recent estimates in other localities. The well-documented near-total absence of internal deformation within the Turkish plate thus does not result from high strength: it results from the geometry of its boundaries which allow them to slip without any need for internal deformation. The main imperfection in this pattern of boundaries results from the high- strength "patch" on the Turkey-Africa plate boundary in southern Turkey. The seismicity in this locality appears correlated with major earthquakes on the NAFZ, suggesting the possibility that this boundary behaves as a "geometrical lock" whose slip, in moderate-sized earthquakes, can permit much larger amounts of slip in much larger earthquakes on the NAFZ. Future detailed monitoring of this region may thus provide the basis for a system of advance warning of future destructive earthquakes on the NAFZ.