| Project/Area Number |
08454123
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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 |
固体地球物理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
FUJIMORI Kunio Kyoto University, Graduate School of Science, Lecturer, 大学院・理学研究科, 講師 (00025470)
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| Co-Investigator(Kenkyū-buntansha) |
OTSUKA Shigeaki Kobe Gakuin University, Faculty of Humanities and Sciences, Professor, 人文学部, 教授 (00122242)
HIGASHI Toshihiro Kyoto University, Graduate School of Science, Instructor, 大学院・理学研究科, 助手 (90135517)
TAKEMOTO Shuzo Kyoto University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (40027256)
福田 洋一 京都大学, 大学院・理学研究科, 助教授 (30133854)
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| Project Period (FY) |
1996 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Hyogo-ken Nanbu Earthquake / earthquake / crustal deformation / active fault / postseismic deformation / groundwater discharge / pore pressure / earth tide / 地下水 / 震源域 / 歪 / 水準測量 / 六甲 / 光波測量 / 湧水量 |
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| Research Abstract |
Continuous observations of crustal strains and tilts have been executed in the stations (Rokko-Takao, Rokko-Syakunage and Rokko-Turukabuto), which are located within the focal region of the 1995 Hyogo-ken Nanbu earthquake (M=7.2). The observation tunnels of the Rokko-Takao and Rokko-Tsurukabuto are crossing with the Manpukuji and Otsuki faults, respectively. In the Rokko-Takao, change in groundwater discharge from the fracture zone of the Manpukuji fault has beeu also measured. In this work, the observations were continued after the earthquake, and the data analysis was done.
At the Rokko-Tsurukabuto station, a maximum strain change of 400μ strain and a maximum height change of 8.7mm caused by the earthquake were observed. Short-term changes or changes immediately before the earthquake were not detected, but a slow decrease of strain rates, small rotations of the maximum strain directions and a relative upheaval of about 0.1mm/year continued for a long time prior to the earthquake. After the earthquake, the Otsuki fault started lateral and vertical dislocations of a rate of 0.1-0.2mm/year. The dislocations are the same sense as the Quaternary movements of the fault.
A post-seismic crustal deformation which has a comparatively long time constant might be observed after a step-like coseismic crustal deformation. As causes where such deformatian is caused, an after-slip in the vicinity of a hypocenter, and a visco-elastic response of the crust to coseismic slipping have been considered. In present research, we consider that the coseismic strain changes generate the coseismic pore pressure changes which corresponds to the strain changes and that the postseismic crustal deformation is caused by groundwater migrations from the high pressure areas to the low pressure areas including the ground surface. The migration rates might be controlled by permeability of those areas.
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