2019 Fiscal Year Final Research Report
Long-term diversity in recurrence intervals of earthquakes and tsunamis and crustal deformations in the Nankai Trough
| Project/Area Number |
16K17818
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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 |
Geology
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| Research Institution | University of Tsukuba |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2020-03-31
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| Keywords | 南海トラフ / 津波堆積物 / 津波 / 地震 |
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| Outline of Final Research Achievements |
To reconstruct prehistoric tsunami records, we conducted paleotsunami survey at Shima City, Mie Prefecture and Mugi Town, Tokushima Prefecture. At the study site in Shima City, we found 3-5 candidate tsunami layers in the strata of 5,500-4,000 cal yr BP. We found 9 candidate tsunami layers at Mugi Town, and 3 of the 9 layers yielded brackish-marine diatoms. In addition, we revealed based on diatom analysis that subsidence had occurred when the 3 layers were deposited. We concluded that the 3 layers in Mugi Town were deposited by tsunamis associated with earthquakes at the Nankai Trough. Age of the 3 tsunami layers are overlap with tsunami layers found at other areas in eastern Shikoku Island. This implies that these tsunamis and crustal movements occurred in association with earthquakes at the Nankai Trough that widely affected eastern Shikoku Island.
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| Free Research Field |
地質学
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| Academic Significance and Societal Importance of the Research Achievements |
牟岐町の成果は南海トラフ沿岸地域で津波と地震性地殻変動が同時に検出された初めての事例である．また，本研究で行われたような津波痕跡の高精度・高確度年代測定は，他地域の地震・津波痕跡と正確に対比することを可能にし，歴史時代・先史時代における地震・津波の再来間隔や規模を明らかにするために欠かせない情報になる．数千年の時間スケールの中で地震・津波の再来間隔や規模を明らかにすることは，より合理的な地震発生確率の算出や被害の予測に資する．
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