Frictional melting processes during subduction zone earthquakes : Inference from pseudotachylytes and high-velocity shear experiments
| Project/Area Number |
17340152
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology |
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Principal Investigator |
UJIIE Kohtaro Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology, Institute for Research on Earth Evolution, Scientist, 地球内部変動研究センター, 研究員 (40359188)
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| Co-Investigator(Kenkyū-buntansha) |
TSUTSUMI Akito Kyoto University, Division of Earth and Planetary Sciences, Professor, 大学院・理学研究科, 助手 (90324607)
YAMAGUCHI Haruka Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology, Institute for Research on Earth Evolution, Research Assistant, 地球内部変動研究センター, 研究推進スタッフ (80359207)
SAKAGUCHI Arito Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology, Institute for Research on Earth Evolution, Researcher, 地球内部変動研究センター, 研究員 (80304666)
HIRANO Nobuo Tohoku University, Graduate School of Environment Studies, Assistant Professor, 大学院・環境科学研究科, 助手 (80344688)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥9,600,000 (Direct Cost: ¥9,600,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2005: ¥7,400,000 (Direct Cost: ¥7,400,000)
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| Keywords | Earthquake / Geology / シュードタキライト / 摩擦熔融 / レオロジー / 高速せん断摩擦 / 沈み込み帯 / 付加体 / 海溝型地震 / 地震発生帯 |
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| Research Abstract |
Pseudotachylyte-bearing fault zones, found in the Shimanto accretionary complex, southwest Japan, developed during subduction or underplating at seismogenic depths. The pseudotachylytes occur in narrow dark veins less than a few millimeters thick that are sharply bounded by foliated cataclasites that originated from a melange. The microstructures of pseudotachylytes are represented by a fragment-laden, glass-supported texture resulting from the rapid cooling of the frictional melt. Transmission electron microscopy reveals the presence of glass in which euhedral microcrystals of mullite are locally developed. The compositions of the pseudotachylyte matrix and the characteristics of the unmelted grains and microlites in the matrix suggest that frictional melting occurred in an illite-rich slip zone with a minimum melting temperature of 1100℃. The viscosities of the frictional melt were calculated from the pseudotachylyte matrix composition as well as the volume fraction and aspect ratio of the unmelted grains. The viscosities at 1100℃ range from 85 to 290 Pa s, and the corresponding shear resistance along a 1-mm-thick melt layer at a slip rate of 1 m/s was 0.1-0.3 MPa. The formation of a melt layer in an illite-rich slip zone can possibly induce large stress drops, increase the slip rate and enhance rupture propagation, which together could affect the earthquake magnitude in a subduction zone.
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Report
(3 results)
Research Products
(9 results)
