| Project/Area Number |
16K01313
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Natural disaster / Disaster prevention science
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Nakada Setsuya 東京大学, 地震研究所, 名誉教授 (60128056)
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| Project Period (FY) |
2016-10-21 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2016: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
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| Keywords | シナブン火山 / 雲仙普賢岳 / 溶岩ドーム噴火 / ブルカノ式噴火 / 溶岩荷重 / 溶岩噴出率 / マグマ過剰圧 / 溶岩過重圧 / 溶岩ドーム / 爆発的噴火 / 噴出率 / 脱ガス速度 / 溶岩の荷重 / 溶岩ドーム・流噴火 / 火砕流 / 溶岩供給率 / 脱ガス効率 / 火山災害 / 噴火推移 / 溶岩ドーム・溶岩流 / 噴火系統樹 |
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| Outline of Final Research Achievements |
Lava dome eruptions occur when the eruption rate is less than several tens of m3/s, and collapsed-type pyroclastic flows are frequently associated with dome growth, but explosive eruptions may occur. The lava dome eruptions at both Sinabung and Unzen volcanoes had eruption rates that decreased exponentially with time, but at Sinabung volcano, explosive eruptions frequently occurred in the latter stage of the activity. At Unzen, a lava spire was formed at the end of the activity, and a thick lava covered the crater, but at Sinabung, the steep topography continued to collapse and the lava spine was not formed. It was suggested that the frequent occurrence of explosive eruptions at Sinabung at a low eruption rate was caused by volcanic gas-rich magma pressure in the upper conduit over the load of lava pile on the crater.
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| Academic Significance and Societal Importance of the Research Achievements |
爆発的なブルカノ式噴火は，火道上部に蓄積する火山ガスに富むマグマ圧がそれを上から押さえる溶岩荷重を上回ることによって起こる。そのため，噴出率の低い溶岩ドーム噴火や水蒸気噴火であっても爆発的噴火は発生する。噴出率が比較的高い時期に，溶岩ドームの大崩壊による火道上部の急減圧によってブルカノ式噴火が誘発されることは知られているが，より低い噴出率であっても，溶岩荷重が不十分であればブルカノ式噴火が頻繁に発生することが本研究で示された。これは溶岩ドーム噴火のリスクを考える上で，活動末期であっても規模の比較的大きな爆発が起こりうるというハザード評価が必要であることを示した。
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