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    Implications of 2007's Earthquake Activity in Egirdir Lake (SW Anatolia) Based on Moment Tensor Solutions and Inversion of Stress State
    (Springer Basel Ag, 2014) Poyraz, Selda Altuncu; Pinar, AlI; Özden, Süha; Tuncer, Mustafa Kemal
    We analyzed the waveforms of the small- to moderate-sized earthquakes that took place in the northern part of the inner Isparta Angle (IA) to retrieve their source parameters and combine these results with the focal mechanism solutions of the larger events that occurred in 2007 in Egirdir Lake at the apex of IA. In total, source mechanisms of 20 earthquakes within the magnitude range 3.5 < M < 5.0 were calculated using a regional moment tensor inversion technique. The inversion of the focal mechanisms yields an extensional regime with a NNE-SSW (N38A degrees E) trending sigma (3) axis. Inversion results are related to a mainly WNW-ESE oriented normal fault beneath Egirdir Lake. The R value of a NNE-SSW extensional regime is 0.562 showing a triaxial stress state in the region. The current stress regime results from complex subduction processes such as slab pull, slab break-off, roll-back and/or retreating mechanism along the Hellenic and Cyprus arcs and the southwestward extrusion of the Anatolian block since the early Pliocene.
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    Öğe
    Late Cenozoic Stress States along the Ganos Fault, NW Turkey
    (Tmmob Jeoloji Muhendisleri Odasi, 2013) Yildiz, Seray Cinar; Özden, Süha; Tutkun, Salih Zeki; Ates, Ozkan; Poyraz, Selda Altuncu; Yesilyurt, Sevinc Kapan; Karaca, Oznur
    The Ganos Fault, has a big earthquake (Ms:7.3 in 1912), as a right-lateral strike-slip fault, a segment of the northern strand of the North Anatolian Fault is elongated a N70 degrees E trend in west of the Marmara Sea between Gazikoy (Tekirdag) and Saros Gulf This study reveals at late Cenozoic stress states by the limit kinematic analysis, inversion of the earthqukes focal mechanism and remote sensing studies' along the Ganos Fault. Result of the kinematics' analysis was carried out a main tectonic regime.. First mainly strike-slip faulting developed under NW-SE trending compressional direction showing by a (sigma(1)) 130 degrees +/- 16 degrees and a (sigma(3)) 53 degrees+13 degrees trends and Rm ration calculated as 0.49. Secondly and consistent with first faulting, a NE-SW trending concurrent extensional direvtion produce a local normal faulting presented by a (sigma(3)) 28 degrees +/- 18 degrees trend in horizontal plane. Furthermore, between 2003 and 2010 years, bigger than M=3.3,12 earthquakes on Ganos Fault and its vicinity, determined the focal mechanisms and inversion analysis results indicate that a strike-slip faulting is active along the fault. In the inversion of the earthquakes, a strike-sliplhulting presented a (sigma(1)) N 2760 degrees +/- 7 degrees and (sigma(3)) N 6 degrees +/- 6 degrees trends and Rm ration calculated as 0.44. This result is consistent with the results of fault kinematic analysis and offer as a transtensional character along the fault. According to rose diagram that was generated by remote sensing lineament analysis. Determined 223 lianements have mainly parallel to the Ganos Fault. The stress states,from remote sensing studies are consistent both fault kinematic analysis and inversion of the earthquakes filocal mechanism results. Ganos Fault is an active strike-slip fault by the transtensional character since Late Pliocene.
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    Öğe
    Tectonic implications of the 2017 Ayvacik (Canakkale) earthquakes, Biga Peninsula, NW Turkey
    (Pergamon-Elsevier Science Ltd, 2018) Özden, Süha; Over, Semir; Poyraz, Selda Altuncu; Gunes, Yavuz; Pinar, Ali
    The west to southwestward motion of the Anatolian block results from the relative motions between the Eurasian, Arabian and African plates along the right-lateral North Anatolian Fault Zone in the north and left lateral East Anatolian Fault Zone in the east. The Biga Peninsula is tectonically influenced by the Anatolian motion originating along the North Anatolian Fault Zone which splits into two main (northern and southern) branches in the east of Marmara region: the southern branch extends towards the Biga Peninsula which is characterized by strike-slip to oblique normal faulting stress regime in the central to northern part. The southernmost part of peninsula is characterized by a normal to oblique faulting stress regime. The analysis of both seismological and structural field data confirms the change of stress regime from strike-slip character in the center and north to normal faulting character in the south of peninsula where the earthquake swarm recently occurred. The earthquakes began on 14 January 2017 (Mw: 4.4) on Tuzla Fault and migrated southward along the Kocakoy and Babakale's stepped-normal faults of over three months. The inversion of focal mechanisms yields a normal faulting stress regime with an approximately N-S (N4 degrees E) sigma 3 axis. The inversion of earthquakes occurring in central and northern Biga Peninsula and the north Aegean region gives a strike-slip stress regime with approximately WNW-ESE (N85 degrees W) sigma 1 and NNE-SSW (N17 degrees E) sigma 3 axis. The strike-slip stress regime is attributed to westward Anatolian motion, while the normal faulting stress regime is attributed to both the extrusion of Anatolian block and the slab-pull force of the subducting African plate along the Hellenic arc.