| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Kajuro Kyoto University, Disaster Prevention Research Institute, Research Associate, 防災研究所, 助手 (20135510)
KOMAZAWA Masao Geological Survey of Japan, AIST, Institute of Geoscience, Chief Researcher, 地球科学情報, 主任研究官
NISHIMURA Keiichi Okayama University of Science, Faculty of Informatics, Professor, 総合情報学部, 教授 (60025468)
NISHIDA Ryohei Tottori University, Faculty of Engineering, Professor, 工学部, 教授 (90027269)
MORIKAWA Hitoshi Tokyo Institute of Technology Interdisciplinary Graduate School of Science and Engineering, Associate Professor, 大学院・理工学研究科, 助教授 (60273463)
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| Research Abstract |
The object of this research is to develop a suitable method to elucidate 3D basement structure of a sedimentary basin with thick soil deposits, using observational data of microseisms and gravity anomaly, aiming at microzonation of urban area for prevention and mitigation of earthquake disaster. Basic idea for studying the configuration of bedrock is (1) estimation of velocity structure from the dispersion of Rayleigh waves with array observation of microseisms, and (2) estimation of depth to bedrock at various sites with horizontal-to-vertical spectral ratio (H/V) analysis. In the basin, array observations are made at several sites, and the resultant velocity structures are interpolated for 3D model using H/V data at many sites in the basin. For array analysis, we have developed a simple technique using only 2 set of seismometers, 2sSPAC method. Bouguer gravity anomaly provides distribution of densities. Thus, we can discuss the structure model with different physical parameters, namely, seismic impedance and density, and can obtain physically reliable structural model. In this research project, we studied various structural basin which had been seriously damaged by earthquakes: Kyoto basin, Ohmi basin, Hiroshima Plain, Yumigahama Peninsula, Tottori Plain, Nara basin, Lijiang basin in Yunnan, China, and Adapazari, Turkey. As a result, it is pointed out that, concentration of severe damage took place in the region where the configuration of bedrock is steep. This is true for all the basins analyzed but Nara basin, because there is no information on damage distribution in Nara basin. In conclusion, our method is considered useful for microzoning sedimentary basin.
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