2006 Fiscal Year Final Research Report Summary
Debris avalanche deposits from Kyogatake Volcano and the recent faulting events in Fukui Prefecture, central Japan.
| Project/Area Number |
16540414
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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 |
Geology
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| Research Institution | University of Fukui |
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Principal Investigator |
YAMAMOTO Hirofumi University of Fukui, Faculty of Education and Regional Studies, associate professor, 教育地域科学部, 助教授 (50240122)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAJIMA Tadashi University of Fukui, Faculty of Education and Regional Studies, professor, 教育地域科学部, 教授 (70093440)
FUJII Junko University of Fukui, Faculty of Education and Regional Studies, assistance, 教育地域科学部, 教務職員 (50228946)
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| Project Period (FY) |
2004 – 2006
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| Keywords | slope failure / Kiotoshi Fault / Tsukaharano upland / Mt.Kyoga-dake / Mt.Hozuki-yama / debris avalanche deposits / active fault / Fukui Prefecture |
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| Research Abstract |
Kyogadake debris avalanche deposits were derived form the west and southwest side of the middle Pleistocene Kyogadake Volcano, and spread over the west to southwest foot of the mountain. The large slope failures have occurred 5 times in recent 50 ka. The oldest failure was generated about 37-46 ka on the west side of the mountain and the debris avalanche spread mainly over the west slope. The next one was 31 ka on the west side and the debris avalanche went down the west to southwest slope. The next three failures occurred on the southwest side of the mountain at 25.30ka, 2.1ka and 5.6-6.0 ka. By the 25.30ka failure, the debris avalanche went down to southwest straight over 10km, and formed the debris plateau called Tsukaharano upland area. The debris avalanches generated by the next two failures also went down to southwest and formed the elongated lob on gentle slope northeast side of Tsukaharano upland area. Small collapse occurred on the western side at 4-5ka.
The dextral strike-slip faults are situated of about 2-4 km southeast of these failures. One of the rupture histories of Kiotoshi fault, which extends N-S at the south side of Tsukaharano upland area, shows the same time as that of the last slope failure. This indicates that the slope failure may have triggered by the rupture of the fault passing southeast side of Mt. Kyogadake.
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