| Co-Investigator(Kenkyū-buntansha) |
伊藤 喜宏 京都大学, 防災研究所, 准教授 (30435581)
飯高 隆 東京大学, 地震研究所, 准教授 (00221747)
岡田 知己 東北大学, 理学研究科, 准教授 (30281968)
岩田 貴樹 常磐大学, 人間科学部, 准教授 (30418991)
行竹 洋平 神奈川県温泉地学研究所, 研究課, 主任研究員 (20435853)
吉田 圭佑 東北大学, 理学研究科, 助教 (20743686)
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| Budget Amount *help |
¥281,580,000 (Direct Cost: ¥216,600,000、Indirect Cost: ¥64,980,000)
Fiscal Year 2018: ¥19,500,000 (Direct Cost: ¥15,000,000、Indirect Cost: ¥4,500,000)
Fiscal Year 2017: ¥41,470,000 (Direct Cost: ¥31,900,000、Indirect Cost: ¥9,570,000)
Fiscal Year 2016: ¥17,550,000 (Direct Cost: ¥13,500,000、Indirect Cost: ¥4,050,000)
Fiscal Year 2015: ¥103,870,000 (Direct Cost: ¥79,900,000、Indirect Cost: ¥23,970,000)
Fiscal Year 2014: ¥99,190,000 (Direct Cost: ¥76,300,000、Indirect Cost: ¥22,890,000)
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| Outline of Final Research Achievements |
We estimated the differential stress in the seisimic zones beneath the Japanese Islands from the precise hypocenter locations and focal mechanism solutions in this study. We found that some active faults cannot slip unless the strength is very small there. We have developed a method to estimate accurate stress fields using P wave initial motion data and verified its effectiveness. Based on the correlation between the topography and the focal mechanism solutions and the stress rotations around the source areas after large earthquakes, we found that the differential stress in the seismic zone is less than 100 MPa, which corresponds to an extremely small frictional coefficient of about 0.1-0.3 assuming hydrostatic pore pressure. We also obtained some evidences showing that such low strength is caused by high pore pressure for earthquake swarms at least.
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