| Project/Area Number |
63540303
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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 |
固体地球物理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
ISHIHARA Kazuhiro Disaster Prevention Research Institute, Research Associate, 防災研究所, 助手 (30027297)
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| Co-Investigator(Kenkyū-buntansha) |
IGUCHI Masato Disaster Prevention Research Institute, Research Associate, 防災研究所, 助手 (60144391)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | Volcanic earthquake / Explosion-quake / Air-shocks / Intrusion of magma / Extrusion of magma / Comparative study / Andesitic volcano / マグマの上昇・発泡 / マグマの上昇・発泡・噴出 / B型地震 / 地盤変動 / ストロンボリ式噴火 |
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| Research Abstract |
1. Classification of Volcanic Earthquakes (B-type) at Sakurajima Volcano Volcanic micro-earthquakes (B-type) are categorized into two types by their predominant frequency: the one is of low frequency (BL:1-3 Hz) and the other is of high frequency (BH:5-8 Hz). BH types are generated at a lower part of the magma conduit on the inflation stages of the summit region, and BL types swarm at a shallower portion of the conduit together with intermittent ejection of volcanic ash and bombs and weak air-shocks in deflationay stages. These results of observations suggest that BH types are related to the intrusion process of magma and BL types are to the extrusion process.
2. A comparative Study of Volcanic Earthquakes at Suwanosejima and Sakurajima (1) Three types of volcanic earthquakes and two types of volcanic tremors are identified at Suwanosejima, as similar as at Sakurajima. The frequency of B-type earthquakes increased about one month before the explosive activity which began in the middle of September, 1989. Such phenomena have been often observed at Sakurajima and other andesitic volcanoes. These results suggest that volcanic earthquakes and tremors have common features at andesitic voleanoes and the volcanic process has a similarity among them. (2) It was revealed that the natures of explosive eruptions at Suwanosejima are between intermittent eruptions related to BL-type swarms and explosive eruptions at Sakurajima in their intensity of air-shocks and seismic waves, in the time-interval of eruptions and in their explosivity. The predominant frequency of seismic waves and air-shocks at Suwanosejima is higher than those at Sakurajima, which may reflect the smaller size of the magma conduit of Suwanosejima than that of Sakurajima.
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