| Project/Area Number |
04650581
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
資源開発工学
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| Research Institution | IWATE UNIVERSITY |
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Principal Investigator |
SAITO Tokumi Faculty of Engineering, Iwate University, Professor, 工学部, 教授 (20113855)
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| Co-Investigator(Kenkyū-buntansha) |
ABE Mamoru Faculty of Engineering, Tohoku University, Associate Professor, 工学部, 助教授 (50005310)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1993: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1992: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Keywords | Geophysical exploration / Geothermal seismic noise / Direction of arrival / Apparent phase velocity / Tripartite metshod / Frequency-wavenumber analysis / Geothermal reservoir / トリパイト法 / 短周期微動 / アレイ観測 / 周波数ー波数解析法 |
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| Research Abstract |
Georthermal seismic propagation at the kakkonda geothermal area and the eastern region of Hachimantai was investigated by the tripartite method and frequency-wavenumber analysis respectively. The direction of arrival and the apparent phase velocity for seismic noise from 1 to 10Hz were investigated.
The conclusions may be summarized as under.
1. No diurnal and secular variations of arrival direction for seismic noise at the kakkonda geothermal area are observed. Arrival quadrants obtained near the steam supply system are changed before and after the closure of wellhead valve of gerthermal prodection wells. Seismic noise in the 3-7Hz is arriving from the direction of geothermal reservoir. Apparent phase velocities for the 1-10Hz seismic noise field show the despersive characteristics and can be explained by the Rayleigh wave dispersion curve. Consequently, it is suggested that seismic noise observed in the Kakkonda geothermal area is the fundamental-mode Rayleigh waves which body waves originating at a reservoir were converted near the surface.
2. Sesmic noise at the eastern region of Hachimantai geothermal area had a uniform direction of arrival and was originated from a relatively deep subterranean area. Apparent phase velocities for the 1-10Hz seismic noise field show the despersive characteristics and can be explained by the Rayleigh wave dispersion curve.
Further evaluation of the effectiveness of geothermal seismic noise survey is required by accumulation of survey data at an increased number of geothermal areas.
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