| Project/Area Number |
23540498
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | University of the Ryukyus |
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Principal Investigator |
ANDO Masataka 琉球大学, 理学部, 客員教授 (80027292)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Mamoru 琉球大学, 理学部, 准教授 (60295293)
SHISHIKURA Masanobu 独立行政法人産業技術総合研究所, その他部局等, 研究員 (00357188)
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| Project Period (FY) |
2011 – 2013
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| Project Status |
Completed (Fiscal Year 2013)
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| Budget Amount *help |
¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000)
Fiscal Year 2013: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2012: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2011: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
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| Keywords | 津波 / 琉球海溝 / 沈み込み帯 / 1771年八重山津波 / 石垣島 / 津波堆積物 / 有孔虫 / 年代測定 / 海溝系地震 / C１４年代測定 / カップリング率 / 掘削調査 / 1771年津波 / C14年代測定 / 石垣宮古島 / 明和の津波 / 津波石 / ジオスライサー / 津波発生間隔 |
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| Research Abstract |
Some subduction zones are associated with large earthquakes but others are not or infrequent The Ryukyu subduction zone is grouped into the extensional group, having the fastest convergence rate (12.5cm/y). In this subduction zone, we obtained a complete set of tsunami layers which were found to be buried in a gentle slope hill. The most recent event corresponds to the 1771 documented in several records. The height documented is 20 m while the highest tsunami layer reaches to 8 m, which are very consistent with historical documents since tsunami sediments below the run-up heights of sea water. The 1771 event was estimated to have occurred near the trench with a fault slip of 20 m. This slip can be accumulated in 160 years if 100% of its relative plate motion is accumulated. However, the intervals we found are 500 and possibly 100 years, significantly longer that this slip. This suggests that the extensional subduction zone has an ineffective accumulation of slip on its interface.
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