| Project/Area Number |
05558048
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Natural disaster science
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| Research Institution | Shizuoka University |
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Principal Investigator |
KOYAMA Masato Shizuoka University, Faculty of Education, Associate Professor, 教育学部, 助教授 (70183811)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAOKA Koshun Nagoya University, Faculty of Science, Associate Professor, 理学部, 助教授 (70183118)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1994: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1993: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Keywords | Tide / Crustal strain / Volcanic activity / Magma discharge volume / Izu Oshima Volcano / Unzen Volcano / Pyroclastic flow / Prediction of volcanic eruption / 歴史噴火 / 地球潮汐 / 海洋潮汐 / 富士火山 |
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| Research Abstract |
This study aimed to examine mechanisms of the synchronism between volcanic activities and the earth and ocean tides, and to evaluate the possibility of a method for predicting volcanic eruptions using the synchronism. For this purpose, we made two approaches : (1) theoretical evaluation of possible mechanisms of the synchronism between volcanic activities and crustal strain including tidal strain ; (2) collection of data of volcanic activities and analysis of the relationships between temporal variations of volcanic activities and variations of tidal force and strain. As for approach (1) , we revealed that crustal strain can generate volcanic activities when the azimuth and amount of the strain give maximum volumetric change to a magma reservoir. This idea is theoretically supported by model calculation and also is demonstrated by the analysis of the relationships between the volcanic earthquakes observed in Izu Oshima Volcano and the crustal strain associated with tectonic earthquakes near the volcano. We also revealed that a cumulative pattern of magma discharge from a volcano can record a history of the eruptions triggered by changes in crustal strain. Concerning approach (2) , we systematically collected historical documents describing the eruptions occurred for the past 1300 years in Izu Oshima Volcano, and revealed that the initiation of the historical eruptions were synchronized with the fortnightly component of the earth tide. We also analyzed the relationships between the tidal strain and the 1991 pyroclastic eruptions in Unzen Volcano and revealed that the tidal strain with an E-W or up-down compressional component triggered large pyroclastic flows during May 24-June 12,1991, when the volcanic activities attained a maximum level. Synthesizing all these results, we clarified problems of the method for predicting volcanic eruptions using the synchronism.
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