Morphotectonics and seismicity in the east of Marmara region, Turkey

摘要

The morphotectonics and seismicity in the east of the Marmara region of Turkey are dealt with in this study. The trough-shaped valleys, rejuvenation points, distortion and different block movements between uplifts are the signs of the multicyclic development. In the north the model of intermediate basins and lens-shaped mountains characterizes the North Anatolian fault zone (NAFZ) tectonics. Towards the south the morphotectonic model is the central-west Anatolia model of the extensional tectonic regime of the Aegean Sea. There is no similarity between the lens-shaped anticline-horst structures of the NAFZ and the southern areas. While the historical and measured larger earthquakes happen on the edge of the main morphostructures which are prone to uplift, the smaller ones occur in the internal parts. The seismicity centers fit the places where the main NE-SW faults get closer or intersect one another, the main faults intersect with the secondary NW-SE faults or where the main NW-SE faults intersect with the en-echelon secondary faults. The earthquakes that caused considerable casualties between 1900 and 2003 mostly occurred in the Izmit Gulf, Adapazari and Duzce basins on the north branch of the North Anatolian fault (NAFN). In other areas (Cinarcik-Gemlik-Bursa-Inegol-Yenisehir), no large seismicity (M > 6) has been reported over this period and this attracts attention. When the historical and large earthquakes are correlated with the seismicity groups and the occurrence time of the historical events is considered, it can be postulated that a possible larger earthquake (M > 6) may occur inside these seismicity groups and/or on the south branch of the North Anatolian fault (NAFS).