Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü

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Browsing Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü by Author "Afacan Ergün, Tuğçe."

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    A tomographic image of the fault zone on the north anatolian fault
    (Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2006., 2006.) Afacan Ergün, Tuğçe.; Karabulut, Hayrullah.
    During the fall of 2003, seismic data were collected in the eastern Marmara Region on the North Anatolian Fault Zone near izmit rupture zone by a controlled source experiment. The fault was clearly exposed on the surface and the thickness of the sediments in the basin is expected to be greater than several hundred meters. The data were acquired along a 1.2 km long nmih-south profile with a total of 50 recorders equipped with 4.5 Hz geophones. 3-component geophones were used near the fault zone to detect trapped waves. The shot spacing was 5 m and receiver spacing was varying from 1Om to 20m. More than 180 shots were fired using a vibroseis. Data were recorded continuously with 1OOHz sampling rate. . This study is a step towards a determination of a shallow P wave velocity structure on the NAFZ near izmit rupture. We applied regularized inversion technique to the first arrival travel times. More than 6500 picks from 129 shot-gathers were used in the analysis. A shallow P wave velocity image (<200m) from travel time tomography was obtained in the izmit basin. The results indicate a fault zone of approximately 100 m thick. A velocity contrast was detected between the fault zone and surrounding blocks. The P wave velocity on the southern block varies between a range 1.4 - 1. 7 km/s and 1. 7 - 2.0 km/s on the northern block the velocity decreases to 1.4 km/s within the fault zone. 3-component recordings and fan shots indicates the presence of the fault zone consistent with the . tomographic image. Previous seismological studies in the region also show that the thickness of the fault zone is on the order of approximately 1OOm.
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    Lithospheric structure of the western Turkey and aegean region
    (Thesis (Ph.D.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Afacan Ergün, Tuğçe.; Karabulut, Hayrullah.
    Aegean-Anatolia region undergoes an intense internal deformation as evidenced by the existence of major active faults, intense seismic activity and the marked thinning of the crust. It makes the region center of attraction to the study the interaction between the deep structure with the surface deformation. The aim of this study is to provide constraints on the crustal and uppermost mantle structure by using seismic data of permanent broad-band network of Kandilli Observatory and Earthquake Research Institute (KOERI-RETMC), and a temporary array of Seismic Imaging beneath Aegean-Anatolia Domain (SIMBAAD) experiment. Seismic stations of Republic of Turkey Prime Ministry Disaster and Emergency Management Presidency (AFAD), Incorporated Research Institutions for Seismology (IRIS) and previous experiment called Western Anatolia Seismic Recording Experiment (WASRE) were used to complement the network. In this regard we present two high resolution lithospheric images along a ~650 km transect crossing western Anatolia at 28°E longitude from the Black Sea to the Mediterranean and a ~550 km transect crossing central Anatolia at 30.5°E longitude. A total of 5250 receiver functions are computed from the records of teleseismic earthquakes at 40 broadband seismic stations for each of the profiles with an average spacing of ~ 15 km. Lateral variations of crustal thickness, Vp/Vs are inferred from both H-K, and common conversion point stacks (CCP). In order to have a better idea on the accuracy of the estimated crustal parameters we also performed a search scheme based on the Neigboorhood Algorithm. The receiver functions are inverted for a 1-D layered medium to determine the layer thicknesses, Vs and Vp/Vs. The CCP images reveals a longwavelength variations of Moho depth from ~31 km in the Thrace basin to ~25 km beneath the Marmara Sea, ~25 km beneath the Menderes Massif and ~20 km on the coast of the Mediterranean on the western Anatolia transcent. On the eastern transect, a smooth Moho topography is observed with a sharp discontinuity at depths ranging from 34 km beneath the Black Sea coast, ~35 km beneath the Sakarya Zone with mafic composition to 43 km beneath the Antalya Bay on the central Anatolia profile. The Moho of the subducted African lithosphere is imprinted between ~40 and ~60 km depth at the southern end of the western Anatolia profile, dipping northward where the subducted Cyprus lithosphere is observed dipping northward with an angle of 40◦ between ~40 and ~100 km depths beneath the Antalya Bay on the central Anatolia transect.