2003 Fiscal Year Final Research Report Summary
Integrated study of material analysis of drilled core and geophysical borehole logging of Chelung-pu fault, Taiwan
| Project/Area Number |
13573009
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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 | 海外学術 |
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| Research Field |
Geology
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KIMURA Gaku The University of Tokyo, Graduate School of Science, Professor, 大学院・理学系研究科, 教授 (80153188)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAGUCHI Arito Institute for Frontier Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Researcher, 固体統合フロンティア研究システム, 研究員 (80304666)
TANAKA Hidemi The University of Tokyo, Graduate School of Science, Lecturer, 大学院・理学系研究科, 講師 (40236625)
ITO Hisao National Institute of Advanced Science and Technology, Senior Researcher, 地球科学情報研究部門, 主任研究員 (10356470)
FUKAHATA Yukitoshi The University of Tokyo, Graduate School of Science, Research Associate, 大学院・理学系研究科, 助手 (10313206)
IKEDA Yasutaka The University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (70134442)
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| Project Period (FY) |
2001 – 2003
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| Keywords | Taiwan / Chelungpu fault / Fault zone drilling / Chi-Chi earthquake / Intrafault materils / Frictional heating |
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| Research Abstract |
Through this integrated research, three research groups, (1) Geophysical logging group, (2) Material analysis group, and (3) Geological investigation group presented the results as follows.
(1) Geophysical logging group : Fiber thermistor was installed into the Nantou Borehole (160m depth). Continuous monitoring of temperature had been performed, which clarified that there was a broad low-temperature region 30 to 40m above the fault surface. This would be caused by inflow of cold ground water into the region from very close to the surface. The permeable region would be enhanced by increase in pore volume by fracturing of rocks by an earthquake. The results of temperature logging performed right after the drilling indicate that broad increase in temperature around the fault zone in both northern and southern boreholes. Coefficients of friction during earthquake slip are estimated using these data to be around 0.2 and 0.8 to the northern and southern fault surface.
(2)Material analysis gro
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up : distribution of fault zone rocks was examined in detail by observations. The results clarified contrasting mode of fault rock distribution between northern and southern fault zones. The fault rocks of northern fault zone are composed of thin (<1cm in thickness) slip layer composed of clay minerals surrounded by thick (>10min thickness) 'random-fabric' fault breccia. Those of southern fault zone are composed of thick (around 1m in thickness) ultra-cataclasite (relict Pseudotachyite fragments are included) zone, surrounded by thick (> 10min thickness) 'foliated' fault breccia. These contrasting characteristics of fault rock distribution may correspond to the contrasting mode of historical slips between northern and southern fault zones.
(3) Geological investigation group : Vitrinite reflectance was utilized to estimate frictional heating within slip zones. Several shear zones around Chelungpu fault was tested by this method. The results clarified that reflectance was raised within a shear zone. Quantitative esitimation will be testified by experiments. Less
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