| Project/Area Number |
15K05341
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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 |
Petrology/Mineralogy/Economic geology
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| Research Institution | Kyoto University |
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Principal Investigator |
Obata Masaaki 京都大学, 理学研究科, 名誉教授 (20126486)
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| Co-Investigator(Kenkyū-buntansha) |
安東 淳一 広島大学, 理学研究科, 教授 (50291480)
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| Research Collaborator |
MASHIMO Tsutomu
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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 |
¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
Fiscal Year 2017: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2016: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2015: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Keywords | 深部地震 / マントル / かんらん石 / 摩擦溶融 / 衝撃圧縮 / シュードタキライト / カタクラサイト / 断層 / 地震 / 衝撃圧縮実験 / オリビン / 粉砕 |
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| Outline of Final Research Achievements |
In order to study mechanism of deep earthquakes, a series of shock compression experiments were performed, using a single crystal of forsterite and a powder gun. Many shear planes were generated in the crystal diagonally to the compression axis and, in one experiment, we observed a clear local melting occurred along shear planes. The microstructural observation of the shear planes revealed that plastically-deformed olivine was pulverized into a few hundred-nanometer size particles within a narrow zone from the shear plane and, locally along the shear plane, have partly melted. Moreover, injection veins filled with olivine melt were found in the fault wall. We interpret that a dynamic pulverization occurred at a running rupture front when the sample was compressed and that melting took place by the friction among the olivine nanoparticles. Pulverization before melting is considered to be a common process in co-seismic faulting and may play an important role in deep earthquakes.
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| Academic Significance and Societal Importance of the Research Achievements |
深部地震発生のメカニズムは地球科学上の第1級の課題である。本研究はかんらん石単結晶を用いた一連の衝撃圧縮実験と回収試料の解析により、地震断層面で摩擦溶融に先行して粉砕が起こることを明らかにした。0.5マイクロ秒という極端に短時間で、塑性変形、剪断粉砕、そして溶融という一連の過程が生じ、また衝撃圧縮下でも断層の先端部では引っ張り応力による破断が生じかんらん石組成のメルトの注入が起こったことが明らかになった。これらのことは学術上全く新しい知見であり、今後の深部地震のメカニズム解明に貢献する成果であるということができる。
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