2014 Fiscal Year Final Research Report
Geological survey of past tsunamis in the earastern margin of the Japan Sea regarding subduction-zone earthquakes
| Project/Area Number |
25870062
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Natural disaster / Disaster prevention science
Geology
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Project Period (FY) |
2013-04-01 – 2015-03-31
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| Keywords | 日本海東縁 / 地震 / 津波 / 堆積物 |
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| Outline of Final Research Achievements |
Tsunami traces in the eastern margin of the Japan Sea was investigated and sandy event layers were discovered from the coastal areas of Yamagata Prefecture. Depositional ages of each layer are 11th and 8-9th century, respectively. The sand layers contain brackish diatoms, implying sediment supply from tidal zones through the rivers. Results of numerical modeling of tsunami generation and propagation showed that earthquake tsunami in the offshore of Yamagata is at most 5 m and cannot explain the sandy event layers. A submarine slope failure, which was identified from bathymetry and bottom profiling data, generates a large-scale tsunami with the height of 20 m near the coastline. The tsunami reaches the survey sites and can explain the possible sandy tsunami deposits. In conclusion, this study demonstrated the possibility of occurrence of a large-scale tsunami during 150-200 years after the 869 Jogan earthquake.
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| Free Research Field |
地球科学
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