Browsing by Author "Can, Birsen."

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    Source properties of micro - earthquakes in eastern Marmara and their connection to the structure of the Çınarcık basın
    (Thesis (Ph.D.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2019., 2019.) Can, Birsen.; Aktar, Mustafa.
    This study mainly focuses on the source properties of micro-earthquakes in Eastern Marmara and their connection to the structure of the Çınarcık Basin, in particular. Throughout this study, Prince Islands Real Time Earthquake Monitoring System (PIRES) Arrays data have been used, which is the closest land site locations to the North Anatolian Fault (NAF) in the Marmara Sea. Only a limited number of small magnitude earthquakes occur in the Çınarcık Basin. Therefore, earthquakes only within an epicentral distance of ~20 km to the arrays have been evaluated considering that Signal to Noise Ratio (SNR) decreases abruptly for further distances. Special methods have been developed and adapted to the PIRES in this study. In this context, advantages of the arrays have been used in all aspects. Array based cross correlation method has been developed for the optimal detection of the small magnitude events which show similarity. Using this method, a systematical search of the foreshocks and aftershocks activities has been performed. This has led to a large improvement of the detection level and revealed large number of earthquake clustering. It became possible to extract many small magnitude events that are buried in the background noise or in the coda of previous events and therefore were missed by the land stations. Since, the main target was to evaluate the performance of the surface arrays against the boreholes, various noise cancelation tools are developed based on the stacking of repetitive observations. These procedures are used for the estimations of the fracture properties of the small events inside the Çınarcık Basin. The fracture properties that have been analyzed are the seismic moment, fracture radius, stress drop, energy and occurrence statistics. Tests are performed to see if the fracture properties are changing in space and time, or show any other characteristic behavior that may be connected to a particular location in the study area. Variations are observed between the stress drop and location of the events. Similarly, foreshock and aftershock occurrence statistics seems also to vary across the Çınarcık Basin. Since, the present data is rather restricted, it is expected that the interpretations are only preliminary. The results obtained imply that this type of analysis will probably be part of the real time monitoring processes in the future, for the purpose of early warning systems.
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    The crustal and upper mantle shear wave velocity structure beneath eastern Turkey using inversion of surface wave dispersion
    (Thesis (M.S.) - Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2005., 2006.) Can, Birsen.; Gürbüz, Cemil.
    In this study, shear wave velocity structure of the crust and upper mantle across a portion of Eastern Turkey was obtained with one station method, using group and phase velocity dispersion of fundamental mode Rayleigh and Love waves. The S wave velocity structure of the Eastern Turkey is estimated beneath the 29 broadband seismological stations that were deployed during the 1999/2001 ETSE experiment. Rayleigh wave phase velocity is measured between 10 and 85 second periods. Phase velocity is 2.75 km/s for 10 second period and it is 3.9 km/s for 85 second period. On the other hand, Love wave phase velocity is measured between 10 and 50 second periods. Phase velocity is 2.8 km/s for 10 second period and 4.40 km/s for 50 second period. According to the results of S wave velocity inversion? it is found that; between 20 and 30 km depth there is a low velocity layer, which has S wave velocity of approximately 3.4 km/s. The thickness of the crust is calculated as 45 km. S wave velocity, gradually increases between 30 km and 45km.