| Project/Area Number |
09554020
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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 | 展開研究 |
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| Research Field |
固体地球物理学
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| Research Institution | Tohoku University |
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Principal Investigator |
HAMAGUCHI Hiroyuki Graduate School of Science, Tohoku Univ., Professor, 理学研究科, 教授 (20004385)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMIZU H. Faculty of Science, kyushu Univ., Professor, 理学部, 教授 (50178985)
TANAKA K. Faculty of Science and Technology, Hirosaki Univ., Professor, 理工学部, 教授 (40003511)
NISHIMURA Takeshi Graduate School of Science, Tohoku Univ., Research Associate, 理学研究科, 助手 (40222187)
TANAKA S. Graduate School of Science, Tohoku Univ., Research Associate, 理学研究科, 助手 (60281961)
UEKI Sadato Graduate School of Science, Tohoku Univ., Associate Professor, 理学研究科, 助教授 (40004501)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥10,200,000 (Direct Cost: ¥10,200,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥9,000,000 (Direct Cost: ¥9,000,000)
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| Keywords | Seismic exploration / Bandai volcano / Controlled seismology / Seismic tomography / P-Velocity / Volcano structure / マグマ探査 / 火山体内部構造 / 3次元速度構造 / 3次元減衰構造 |
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| Research Abstract |
The knowledge of subsurface structure is indispensable to understand an eruptive mechanism of volcano and to increase reliability of prediction of volcanic prediction We have developed the data logging system with small-size, lightweight and high performance and, in the present study, we applied this system to explore the subsurface structure at Bandai volcano, The research group for seismic exploration of Bandai volcano consisted of 10 national universities and JMA 76 members from the above institutions participated in the present experiment. We deployed 292 temporary unattended seismic stations in and around the volcano within 15 km from the summit and observed seismic waves loin 8 explosions that were fired at 10 minutes interval from 102 till 2 : 12 on October 2,1997. We determined three-dimensional P-wave velocity structure inverted from about 2300 first arrival time data The present results are summarized as follows ; (1) the subsurface velocity beneath Bandai volcano and its neighborhood has a large horizontal velocity contrast. At the elevation of 0.5 km above the sea level, P wave velocity is 5.3 km/s beneath the Numano-taira crater, while it decreases to 2-2.4 km/s in the region between the southern flank of Banadai volcano and lake Inawashire. (2) Narrow high velocity body extending vertically is detected just under the Numano-taira miter. This body is much localized feature, similar to intrusive dyke-like and has horizontal extent less than 2 km. (3) This intrusive body is encircled by the convexities of horseshoe shaped caldera wall associated with the past gigantic eruptions. This suggests that the dyke-like intrusion from depths had worked as source of the past destructive explosions.
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