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Bedrock structure in Adapazari, Turkey—a possible cause of severe damage by the 1999 Kociaeli earthquake |
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| Authors: | Masao Komazawa Hitoshi Morikawa Kajuro Nakamura Junpei Akamatsu Keiichi Nishimura Sumio Sawada Ayfer Erken Akin Onalp |
| Institution: | a Geological Survey of Japan, 1-1 C7, Higashi, Tsukuba, Ibaraki 305-8567, Japan b Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan c Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan d Faculty of Informatics, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan e Faculty of Civil Engineering, Istanbul Technical University, Masiak, Istanbul, Turkey f Faculty of Engineering, Sakarya University, Esentepe Campus, 54040, Sakarya, Turkey |
| Abstract: | The 1999 Kocaeli earthquake brought serious damage to downtown of Adapazari. To study why strong motions were generated at the town, a bedrock structure was investigated on the basis of Bouguer gravity anomaly, and SPAC and H/V analyses of microseisms. It was revealed that, the basin consists of three narrow depressions of bedrock with very steep edges, extending in E–W or NE–SW directions along the North Anatolia faults, and the depth to bedrock reaches 1000 m or more. Downtown of Adapazari is located 1–2 km apart from the basin-edge. It is considered that, the specific configuration of bedrock amplifies ground motions at the downtown area by focusing of seismic waves and/or interference between incident S-waves and surface-waves secondarily generated at the basin-edge. Studying 3D bedrock structure is an urgent issue for microzoning an urban area in a sedimentary basin. |
| Keywords: | Bouguer anamaly 3D gravity-basement Spatial auto-correlation method Horizontal-to-vertical spectral ratio of microseisms Basin-edge effect Focusing of seismic waves North Anatolia faults 1999 Kocaeli earthquake |
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