| Project/Area Number |
17K05626
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2017: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Keywords | 深発地震 / 脱水 / 相似地震 / 蛇紋岩化 / メカニズム解 / 相転移 / 脱水脆性化 |
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| Outline of Final Research Achievements |
We investigated the genesis of intraslab earthquakes beneath the Japanese Islands using high-quality waveform data recorded at a dense seismograph network. The analysis included the earthquake relocations, determination of focal mechanism solutions, and estimates of stress drop and earthquake radiation energy of deep-similar earthquakes. The wide range of source parameters estimated for deep similar earthquakes in a common slab environment suggests that source parameters can be significantly affected by small-scale heterogeneities along the fault. A dual process which includes seismic rupture assisted by both fluid-related embrittlement and thermal shear instability may explain the wide range of source parameters estimated in this study. Beneath Kyushu, the genesis of intraslab earthquakes is locally affected by the subduction of the ridge subduction and regionally governed by the along‐arc variation in the formation age of the incoming plate.
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| Academic Significance and Societal Importance of the Research Achievements |
一般にスラブ内地震の震源は深いため，浅い地震に比べ被害が生じることは少ない．しかしながら，スラブ内地震でも1987年千葉県東方沖地震のように犠牲者がでる場合もあり，また高周波の揺れが励起されることで木造家屋への被害が生じることもある．本研究では発生メカニズムの理解が遅れているスラブ内地震に焦点を当て研究を行った．得られた結果は，スラブ内地震はこれまで考えられてきた以上に震源パラメータ（地震の特性）が多様であり，一律的な理解では限界があることを示している．大地震の発生が危惧されている首都直下などいくつかの領域においてさらに調査を進めることで，地震発生メカニズムの理解が進むと期待される．
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