Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü

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Browsing Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü by Author "Aksarı, Doğan."

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    Analysis of 15 December 2000 and 3 February 2002 Sultandağı - Afyon earthquakes
    (Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Aksarı, Doğan.; Karabulut, Hayrullah.
    We analyzed two moderate size of earthquakes (Mw=6.0, Mw=6.5) occurred in Sultandağı-Afyon, southwestern Turkey on December 15, 2000 and February 3, 2002. Both earthquakes took place on the Sultandağı fault (SF) having normal mechanism with slightly different orientations and same directivities. Both earthquakes ruptured to the northwest of SF. The distance between the epicenters of two events was less than 16 km. We relocated the large magnitude aftershocks and used the closest broadband station (ISP – Isparta Station) to reveal the differences in the directivity. Coulomb stress changes for December 15, 2000 earthquake were calculated and its effect on February 3, 2002 event was explored. It was observed that the December 15, 2000 event increased Coulomb stress up to 4 bar in the area of February 3, 2002 and favored the 2002 rupture. Following both earthquakes, we observed seismic activity triggered in 40 km far from the first mainshock and 25 km from the second. It is considered that the activity took place as a result of dynamic triggering.
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    Determination of upper mantle heterogeneity beneath Aegean-Anatolian region from travel time tomography
    (Thesis (Ph.D.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Aksarı, Doğan.; Karabulut, Hayrullah.
    The objective of this work is to determine the heterogeneities of the upper mantle in the Aegean-Anatolian domain using teleseismic tomography. A waveform dataset was prepared from 798 teleseismic earthquakes with magnitudes greater than 5.5 between January 2004 and December 2015. 417 stations from permanent and temporary networks with more than 64,000 direct P phases are used in the computations. The relative travel times of P waves with respect to the ak135 (Kennett et al. 1995) earth model are computed using waveform cross-correlations technique. The tomographic images are computed as perturbations with respect to ak135 earth model. An algorithm named as fast marching method (FMM) (Sethian, 1996a, 1996b) based on the solution of Eikonal equation is used in the forward computation of the travel times. The inversion is performed using subspace inversion scheme. Trade-off curves are plotted and several synthetic tests are performed in order to select optimum parameters (damping and smoothing) for tomography and the resolution and model roughness were investigated. The tomographic images obtained to a depth of 700 km. The computed tomographic images show a heterogeneous upper mantle structure in the Aegean-Anatolian domain. The results are similar to the previously published images mostly but provides higher resolution for the study area. Both Hellenic and Cyprus subductions are imaged to the depth of 700 km. The tear (Pliny-Strabo Tear) between two subduction zones is clearly observed reaching to 660 km discontinuity. A smaller scale tear (Antalya Bay Tear) is also observed on the Cyprus slab around Paphos Transform Fault. The Anatolian plate is underlined by low velocity mantle material with thickness increasing from west to east. The northern block of the North Anatolian Fault (NAF) is observed as high velocity body observable to a depth of 100-200 km. NAF has a sharp velocity contrast between the north and south.