2003 Fiscal Year Final Research Report Summary
TITLE OF PROJECT : Study on reactivation mechanism of geological faults and prediction of bedrock disaster in the western Chugoku District, southwest Japan
| Project/Area Number |
12680463
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | Yamaguchi University |
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Principal Investigator |
KANAORI Yuji Yamaguchi Univ., Faculty of Science, Prof., 理学部, 教授 (60194883)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIDA Tsuyoshi Yamaguchi Univ., Faculty of Engineering, Prof., 工学部, 教授 (10232307)
MIYATA Yuichiro Yamaguchi Univ., Faculty of Science, Assoc.Prof., 理学部, 助教授 (60253134)
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| Project Period (FY) |
2000 – 2003
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| Keywords | Western Chugoku District / Tectonic basin / Fault movement / Fault rocks / Stress change / Structural analysis / Bedrock disaster / Reactivation |
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| Research Abstract |
Seismic risk of active and geologic faults belonging to the NE-SW-trending West Yauneyama Lake Ohara fault system in Western Chugoku Distirct was evaluated, to mitigate seismic hazards that were induced by inland earthquakes. Topographical surveys and field mapping were performed for all the constituent active and geologic faults and characteristics and surface distributions of cataclasite and gauge zones accompanying those faults were clarified. Based on the structural analysis of the fault rocks, faults which constitute the West Yauneyama Lake Ohara fault system has inverted into the right-lateral motion from the left-lateral motion during the Middle Pliocene
Three destructive inland earthquakes of JMA magnitudes 5 to 6 have successively occurred in central-western Yamaguchi Prefecture dubbing the receipt fifteen years. Following the 1987 M=5.2 Central Yamaguchi Prefecture earthquake, the M=6.0 Suo-nada earthquake and the M=6.1 Northern Yamaguchi Prefecture earthquake in 1991 and 1997, respectively, were strong enough to cause moderate damage on houses. The epicenters of these three earthquakes were located along the active West Yauneyama-Lake Ohara fault system. We calculated the stress changes in the Coulomb Failure Function (CFF) induced by the three successive earthquakes, in order to evaluate seismic risk in and around this fault system. This calculation indicated that by the occurrence of these three earthquakes the stress increased in an approximately 10 to 30-km wide area along the Vest Yauneyama Lake Ohara fault system. The maximum stress increase was estimated to be 0.46 MPa at the Sakota-Ikumo fault. The stress also increased at the Eastern Mt. Mitsugatake fault. In contrast, the post-seismic stress decreased along the Tokusa-Jifuku, the Lake Ohara and the Shibuki faults. No stress change was produced on the Kikugawa fault
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Research Products
(37 results)
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[Publications] Fabbri, O., Iwamura, K., Matsunaga, S., Coromina, G, Kanaori, Y.: "Distributed strike-slip faulting, block rotation, and possible intracrustal vertical decoupling in the convergent zone of southwest Japan."Special Publication of the Geological Society of London.. (accepted). (2004)
Description
「研究成果報告書概要(和文)」より
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[Publications] Fabbri, O., Iwamura, K., Matsunaga, S., Coromina, G., Kanaori, Y.: "Distributed strike-slip faulting, block rotation, and possible intracrustal vertical decoupling in the convergent zone of southwest Japan (Special Publication of the Geological Society of London)"Special Publication of the Geological Society of London. (accepted). (2004)
Description
「研究成果報告書概要(欧文)」より
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[Publications] Mizuno, K., Shimokawa, K., Tsukuda, E., Komatsubara, T., Niimi, K., Inoue, M., Kinoshita, H., Matsuyama, N., Kanaori, Y.: "Preliminary report on geological surveys for the activities of the Oharako fault zone, Yamaguchi Prefecture"Annual Report on Active Fault and Pa leoearthquake Researches, Geological Survey of Japan/AIST. 3. 175-184 (2003)
Description
「研究成果報告書概要(欧文)」より
