Yazar "Yilmaz, Huseyin" seçeneğine göre listele

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    Kinematics of the East Anatolian Fault Zone between Turkoglu (Kahramanmaras) and Celikhan (Adiyaman), eastern Turkey
    (Springer, 2006) Yilmaz, Huseyin; Over, Semir; Özden, Süha
    In this study we determined the stress regime acting along the East Anatolian Fault Zone between Turkoglu (Kahramanmaras) and Celikhan (Adiyaman), from the Neocene to present-day, based on the inversion of striations measured on faults and on the focal mechanisms of earthquakes having magnitudes greater than 5.0. The inversions yield a strike-slip stress regime with a reverse component (i.e., transpression) operative in the Neocene to present with a consistent N-to NW-trending or, axis 156 +/- 11 degrees and an E- to NE-trending sigma(3) axis, sigma(7) 9 degrees sigma(3), producing left-lateral motion along the East Anatolian Fault Zone. The inversions of focal mechanisms yield a strike-slip stress deviator characterized by an approximately N-S (N1 degrees W)-trending sigma(1), and an approximately E-W (N89 degrees E)-trending sigma(3) axis. Both the kinematic analysis and structural observations indicate that the stress regime operating in the study area has had a transpressional character, giving rise to the Mio-Pliocene compressive structures (reverse faults, thrusts and folds) observed in the study area. Field observations allow estimation of a Pliocene age for the strike-slip East Anatolian Fault Zone.
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    Late cenozoic stress field in the Cameli Basin, SW Turkey
    (Elsevier, 2010) Over, Semir; Pinar, Ali; Özden, Süha; Yilmaz, Huseyin; Unlugenc, Ulvi Can; Kamaci, Zuheyr
    A history of deformation has been determined for the Cameli Basin located in the western part of the major Fethiye-Burdur Fault Zone, interpreted as the on-land continuation of Pliny-Strabo fault system (e.g., eastern boundary of the Hellenic Arc). Inversion of fault slip vectors affecting Mio-Pliocene to Quaternary formations in the Cameli Basin, in the southwestern segment of the transtensional Fethiye-Burdur Fault Zone, yields two different normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes; a NW-SE (N129 +/- 19 degrees E) sigma(3) axis and a NE-SW (N50 +/- 16 degrees E) sigma(3) axis. The orientation of fault sets is predominantly around the NE-SW direction in the major Fethiye-Burdur Fault Zone, making the extension NW-SE. The mean R values are 0.74 and 0.69 for both extensions indicating a triaxial stress state, which is clearly different from radial extension and from transitional to strike-slip stress state. The NW-SE extension is probably responsible for the formation of the Cameli Basin during Mio-Pliocene time. In contrast, the inversion of focal mechanism solutions of shallow earthquakes occurring within the Cameli basin identifies a present-day, predominantly extensional stress regime, characterized by an approximately N-S (N184 degrees E) sigma(3) axis, which has an R value of 0.637 indicating a triaxial stress state. The nearly orthogonal extensional stress regimes seem to have been acting contemporaneously with each other at different intensities from the Mio-Pliocene onwards in SW Turkey. This may be attributed to the geodynamic effects related to the subduction of the African plate beneath Anatolia, diffusing along Hellenic and Cyprus arcs and in the west-southwestward extrusion of Anatolia. Our hypothesis is that the cause of the early NW-SE extension is the slab-pull force due to the subduction process along the Cyprus arc, considered to be dominant up to Plio-Quaternary. The later NE-SW to present-day similar to N-S extension, dominant since the Plio-Quaternary, is related to the combined forces of the Anatolian extrusion and the subduction process along the Hellenic arc. (C) 2010 Elsevier B.V. All rights reserved.
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    Late Cenozoic stress state distributions at the intersection of the Hellenic and Cyprus Arcs, SW Turkey
    (Pergamon-Elsevier Science Ltd, 2016) Over, Semir; Özden, Süha; Pinar, Ali; Yilmaz, Huseyin; Kamaci, Zuheyr; Unlugenc, Ulvi Can
    The history of the Late Cenozoic stress regime was determined for an area between the gulfs of Fethiye and Antalya. Fault kinematic analysis and inversion of focal mechanisms of shallow earthquakes reveal significant evolution of the regional stress regime in SW Anatolia, i.e., the area of interaction between the Hellenic and Cyprus arcs, from the Mio-Pliocene to the present time. Fault kinematic analysis yields two different normal faulting stress regimes along the southwestern part of Fethiye-Burdur Fault zone, e.g., in and around cameli Basin (Zone Al) and two different strike-slip to normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes between Fethiye and Demre (Zone B) with an older NW-SE al axis for Mio-Pliocene and a younger NE-SW sigma 3 axis for Plio-Quaternary time. Inversion of focal mechanisms of the earthquakes occurring in Zone Al provideS an extensional stress. state with approximately N- sigma 3 axis. Inversion of those occurring in Zone B, south of Zone Al, yields a dominantly strike-slip stress state with a NE-SW sigma 3 axis and a NW-SE A1 axis respectively. The inversion slip vectors from fault planes yield a consistent normal faulting stress regime in Burdur Basin and its surroundings (i.e., along the northeastern part of Fethiye-Burdur Fault Zone, (Zone A2)) during Plio-Quaternary, continuing into recent time as indicated by earthquake focal mechanism inversions. Both states-have a consistent NW-SE cs3 axis. Fault kinematic analysis indicates NW-SE extension acting in Zone C (subarea between Demre and Antalya), south of Zone A2, during Mio-Pliocene time. The inversion of focal mechanisms yields normal faulting also characterized by a consistent NW-SE sigma 3 axis. The nearly orthogonal extensional stress regimes (NW-SE and NE-SW) obtained by inversion of both measured and seismic faults seem to have been acting contemporaneously with each other at different intensities from the Mio-Pliocene onwards in SW Turkey. This may be attributed to the geodynamic effects related to the subduction of the African plate beneath Anatolia diffusing along the Hellenic and Cyprus arcs and in the west-southwestward extrusion of Anatolia. The cause of the early NW-SE extension is the slab-pull force due to the subduction process along the Cyprus arc, considered to be dotninant until the Plio-Quaternary in the western part of the study area in zones A1 and B. The dominant status of the Cyprus arc continues today in the eastern part of study area in zones A2 and C. The later NE-SW to present day approximately N-S extension, dominant since the Plio-Quaternary, is related to the combined forces of the Anatolian extrusion and the subduction process along the Hellenic arc. (C) 2016 Elsevier Ltd. All rights reserved.
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    Plio-Quaternary stress regime in Esen Cay Basin, SW Turkey
    (Geological Soc Publishing House, 2013) Over, Semir; Özden, Süha; Yilmaz, Huseyin; Pinar, Ali; Unlugenc, Ulvi Can; Kamaci, Zuheyr
    The Plio-Quaternary Esen Cay Basin is situated at the junction of Hellenic and Cyprus arcs in southwestern Turkey. The basin is important for understanding the tectonic evolution of the region in relation to the Hellenic and Cyprus arcs. Fault data from unconsolidated Pliocene and Quaternary deposits, as well as from pre-Pliocene lithologies, are analysed in order to reconstruct the evolution of the stress field evolution from Pliocene onwards. Inversion of measured fault slip vector data identifies two main stress states: extensional and strike-slip. Both states are characterized by a NE-SW-trending minimum horizontal stress axis (sigma(Hmin) = sigma(3)). The mean R value is 0.67, indicating a triaxial state of stress. The inversion also indicates the existence of extensional and strike-slip faulting characterized by a NW-SE-trending sigma(3) axis. This indicates a change in the direction of the minimum horizontal stress axis (sigma(3)) from a NW-SE-trending sigma(3) that dominated prior to Quaternary to a NE-SW-trending sigma(3) that dominated during Quaternary up to actual time.
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    Plio-Quaternary Stress State in the Burdur Basin, SW-Turkey
    (Elsevier, 2013) Over, Semir; Yilmaz, Huseyin; Pinar, Ali; Özden, Süha; Unlugenc, Ulvi Can; Kamaci, Zuheyr
    This study defines the Plio-Quaternary to present day stress regime in the Burdur Basin, located at the northeastern end of the Fethiye-Burdur Fault Zone in SW Turkey. This fault length, which is considered the landward continuation of the Pliny-Strabo trench, is an important feature in SW Turkey. The inversion slip vectors measured on fault planes indicate a consistent normal faulting stress regime during Plio-Quaternary time, continuing into recent times as indicated by earthquake focal mechanism inversions. Both states have consistent NW-SE trending horizontal minimum stress axes (sigma(3)). The orientation of fault sets is predominantly around the NE-SW direction in the major Fethiye-Burdur Fault Zone, making the extension NW-SE. The mean stress ratio is 0.74 indicating a triaxial stress state, which is clearly different from radial extension. The NW-SE extension is probably responsible for the formation of the Burdur Basin during Plio-Quaternary time. This extension, which is probably caused by slab-pull force due to the subduction process along the Cyprus arc, produces a dominant normal motion along the FBFZ. (C) 2013 Elsevier B.V. All rights reserved.
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    Preliminary seismic microzonation of Sivas city (Turkey) using microtremor and refraction microtremor (ReMi) measurements
    (Springer, 2013) Buyuksarac, Aydin; Bektas, Ozcan; Yilmaz, Huseyin; Arisoy, M. Ozgu
    Sivas city, located in the inner east part of Anatolia (Turkey), is far from seismic sources. However, the city is under risk owing to strong earthquakes occurring around the area, and different soil conditions that can produce variation in the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be achieved by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Sivas, based on the variation in the dominant periods of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 114 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with those obtained from refraction microtremor measurements at two profiles crossing the studied area. According to the classification of dominant periods, Sivas area can be divided into four zones, probably prone to different levels of seismic hazard. However, specific studies including analysis of weak earthquakes are required in the future to validate our microzonation map.
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    Upper crust response to geodynamic processes beneath Isparta Angle, SW Turkey: Revealed by CMT solutions of earthquakes
    (Elsevier, 2016) Over, Semir; Özden, Süha; Kamaci, Zuheyr; Yilmaz, Huseyin; Unlugenc, Ulvi Can; Pinar, Ali
    The Isparta Angle is an important area of SW Anatolia where extensions in all directions (N-S, NE-SW, NW-SE and E-W) meet These extensions were determined by normal faulting structures as well as by shallow earthquakes. All extensions, except the E-W one, were attributed to the deviatoric stresses in relation to slab forces and/or extrusion of Anatolia. The moment tensor inversion of 40 shallow earthquakes which occurred in the inner part of the Isparta Angle give focal mechanisms mostly indicating normal faulting. Inversion of all focal mechanisms of the earthquakes obtained from the moment tensor inversion yields normal faulting characterized by an approximately E-W (N268 degrees E) sigma(3) axis. The calculated stress ratio R is 0.6944 indicating a triaxial stress state. Commonly accepted geodynamic models for the eastern Mediterranean region do not include plate boundary forces acting in the east or west direction. Our hypothesis is that the cause of the E-W extension is the combined forces of Gravitational Potential Energy and the hot asthenosphere upwelling through a tear fault in the subducted African plate between the Hellenic and Cyprus arcs beneath the Isparta Angle. (C) 2016 Elsevier B.V. All rights reserved.