HR: 1340h
AN: S23B-0250    [Abstracts]
TI: A Tomographic Image of the Fault Zone on the North Anatolian Fault
AU: * Afacan Ergun, T
EM: afacan@boun.edu.tr
AF: Bogazici University Kandilli Observatory and Earthquake Research Institute, Cengelkoy, Istanbul, 34684 Turkey
AU: KARABULUT, H
EM: kara@boun.edu.tr
AF: Bogazici University Kandilli Observatory and Earthquake Research Institute, Cengelkoy, Istanbul, 34684 Turkey
AU: OZALAYBEY, S
EM: Serdar.Ozalaybey@mam.gov.tr
AF: TUBITAK Marmara Research Center, Earth and Marine Science Institute,Gebze, TUBITAK Marmara Research Center, Earth and Marine Science Institute,Gebze, Kocaeli, 41470 Turkey
AB: During the fall of 2003, seismic data were collected in the eastern Marmara Region on the North Anatolian Fault Zone near Izmit rupture zone. 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 north-south profile with a total of 50 recorders equipped with 4Hz and 12Hz 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 10m to 20m. More than 180 shots were fired using a vibroseis. Data were recorded continuously with 100Hz sampling rate. We applied a least square inversion technique to the first arrival travel times. More than 6000 picks from 180 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 average P wave velocity on the southern block is about 1.7 km/s and 1.9 km/s on the northern block The velocity decreases to 1.3 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 fault zone is on the order of approximately 100m. We compare the results from the shallow tomographic image and the observations from microearthquake activity in the same area.
DE: 6982 Tomography and imaging (7270, 8180)
DE: 7270 Tomography (6982, 8180)
DE: 8180 Tomography (6982, 7270)
SC: Seismology [S]
MN: Fall Meeting 2005