2004 Fiscal Year Final Research Report Summary
Evaluation of recurrent intervals of Nankai Earthquakes recorded in lake and marsh sediments
| Project/Area Number |
15340170
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Kochi University |
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Principal Investigator |
MATSUOKA Hiromi Kochi UNIV., faculty of Science, associate professor, 理学部, 助教授 (60222296)
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| Co-Investigator(Kenkyū-buntansha) |
OKAMURA Makoto Kochi UNIV., faculty of Science, professor, 理学部, 教授 (10112385)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Tsunami sediments / Nankai earthquakes / recurrent intervals / 再来周期 / 地震 |
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| Research Abstract |
The Nankai earthquakes are interplate earthquakes along the Nankai Trough and one of the most historically documented earthquakes in the world. Nine Nankai earthquakes have been identified from historical documents after the Hakuho-Nankai earthquake at A.D.687(Usami,1996;Tuji,1999). The purpose of this study is to reveal pre-historical occurrences of the Nankai earthquakes by using geological evidence.
A small pond named Tadasuga-ike located in the southern. Shikoku Island is selected for this study. The last Nankai earthquake of 1946,Tadasuga-ike subsided coseismically and was covered by seawater of tsunami.
We collected six 5m long sediment cores from the pond and identified fourteen layers of tsunami sediments. Radiocarbon datings indicated these layers deposited during the time period between 1300 yBP and 3800 yBP. These results suggest the recurrence intervals of the Nankai earthquakes are 230 years in average rate during the last 4000 years.
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