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5. - 8. März 2012
DDC:
550 - Earth sciences
Abstract:
The North Anatolian Fault Zone (NAFZ) below the Sea of Marmara represents a 'seismic gap' where a major earthquake is expected to occur in the near future. The Marmara segment of the NAFZ is located between the 1912 Ganos and 1999 Izmit ruptures and is the only segment that has not ruptured since 286 - Seismologie - Naturgefahren und Geophysikund Geophysik 1766. To monitor the microseismic activity at the main fault branch offshore of Istanbul below the Cinarcik Basin a permanent seismic network (PIRES) was installed in 2006 on the Princes Islands, at a few kilometers distance to the main fault branch. PIRES recordings are combined with data from local permanent stations of the Turkish network and the ARNET seismic network on the Armutlu peninsula in order to get the best available azimuthal control for the target area. We obtain a well-resolved hypocenter catalog of microseismicity allowing us to discriminate seismically active from inactive fault patches along the eastern part of the Marmara seismic gap. The results show that the seismicity generally tends to cluster slightly off the main fault, probably along splay faults, with a well-defined internal spatiotemporal migration. This probably means that the main fault is locked and the slip is transferred to secondary structures which might be due to the major NAFZ branch approaching a late stage of the seismic cycle. Furthermore, PIRES recordings are also used for characterization and preselection of borehole locations in the frame of the ICDP-GONAF project aiming at installing a downhole geophysical observatory throughout the eastern Marmara region.
