| Project/Area Number |
15K17746
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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 |
Solid earth and planetary physics
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Tanaka Yoshiyuki 東京大学, 大学院理学系研究科(理学部), 准教授 (90508350)
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| Project Period (FY) |
2015-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2017: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2016: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Fiscal Year 2015: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
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| Keywords | スロースリップ / 潮汐 / 海溝型地震 / 地殻変動 / 重力 |
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| Outline of Final Research Achievements |
An 8.85-year periodicity associated with the lunar orbital motion is seen in the occurrence time of historical large earthquakes with M>7.5 over eastern Japan. However, why such a weak tide triggers earthquakes has not been known. In this study, we found a mechanism that can explain how the effect of a slow, weak tide is enhanced. We confirmed that decadal variations in the ocean and crustal fluid flow, when combined with short-period stronger tides, accelerates/decelerates the plate subduction speed near the source region of mega-thrust earthquakes, resulting in the change of the probability of earthquake occurrence.
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| Academic Significance and Societal Importance of the Research Achievements |
海溝型大地震の発生時期の確率的な見積もりには、３０年以内に何十パーセントという表現がよく用いられる。本研究は、潮汐が地震を誘発するメカニズムを明らかにすることで、地震がより起きやすい時期、起きにくい時期を数年の時間スケールで見積もることのできる中期予測の手法を切り開くものである。本研究の結果は、例えば、海洋変動の一例である黒潮大蛇行を予測することで、その後の地震発生確率の変動をある程度予測することが可能になることを示唆している。
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