| Project/Area Number |
12800019
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| Research Category |
Grant-in-Aid for Special Purpose.
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| Allocation Type | Single-year Grants |
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| Research Institution | Hirosaki University |
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Principal Investigator |
SATO Tamao Faculty of Science and Technology, Hirosaki University, Professor, 理工学部, 教授 (40111223)
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| Co-Investigator(Kenkyū-buntansha) |
MIYASHITA Kaoru Fac. of Sci., Ibaragi Univ., Associate Professor, 理学部, 助教授 (10134165)
MORI James,jiro DPRI, Kyoto Univ., Professor, 防災研究所, 教授 (50314282)
NAKATA Takashi Hiroshima Univ. Dept. of Geography, Professor, 文学部, 教授 (60089779)
HISADA Yoshiaki Dept. of Architecture, Kogakuin Univ., Associate Professor, 工学部, 助教授 (70218709)
MURAKAMI Hitomi Graduate School of Sci. and Engineering, Yamaguchi Univ., Associate Professor, 理工学研究科, 助教授 (10201807)
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| Project Period (FY) |
2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Keywords | West India earthquake / intra-plate earthquake / active faults / aftershocks / post-seismic crustal deformation / GPS / masonry dwelling / earthquake disaster / 大地震の余効地殻変動 / 強震動 |
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| Research Abstract |
Search for a surface fault associated with the earthquake was made over an epicentral area, especially along known active faults. But we could not find any surface faults that might have extended from the causative fault at depth. We found by trenching that the pressure ridge discovered in the north of Budarmora village was caused by lateral spreading of surface layer. A temporary seismograph network consisting of 8 stations was installed to monitor the aftershock activity. Recorded aftershocks are distributed in a depth range of 10 to 35 km ; i. e., the mid-to lower crust. It is inferred from this observation that the causative fault did not reach the the surface. The aftershocks are concentrated on a southerly dipping plane, which suggests that the earthquake was caused by a reverse fault dipping southward. An array of 14 GPS stations was set in and around the epicentral area to detect a post-seismic crustal deformation. Vertical displacements of a few centimeters were observed after a time interval of two months.
Damage distribution was estimated investigating damage levels of different building types as defined by MSK intensity and questionnaire intensity survey, cause of damage in RC and masonry buildings, pattern of ground failure and lifeline structures, micro-tremor observation of site effects and buildings. Estimated isoseismals indicate maximum MSK intensity 10 in an area with a diameter of 50km with its center at Bhachau, and decrease to intensity 6 in Ahmedabad which is 210km distant from the epicenter. Fatality ratio was 6.5 % and highest in Bhachau district and 1.6 % in Bhuj district. The cause of the humanitarian disaster was mostly related with the collapse of masonry dwellings. In the case of RC structures, soft story effects and insufficient strengthening bars were found to have caused damages, while RC structures built after the 1956 Anjar earthquake in Ghandhidam indicated better quality and performance.
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