2018 Fiscal Year Final Research Report

Study of island-forming eruption at Nishinoshima based on remote multi-fields observation

Research Project

PDF

Project/Area Number	16H02221
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Research Field	Solid earth and planetary physics
Research Institution	The University of Tokyo
Principal Investigator	TAKEO Minoru 東京大学, 地震研究所, 教授 (00197279)
Co-Investigator(Kenkyū-buntansha)	杉岡裕子神戸大学, 理学研究科, 准教授 (00359184) 前野深東京大学, 地震研究所, 准教授 (20444078) 大湊隆雄東京大学, 地震研究所, 准教授 (70322039) 高木朗充気象庁気象研究所, 火山研究部, 室長 (70354537) 篠原雅尚東京大学, 地震研究所, 教授 (90242172) 篠原宏志国立研究開発法人産業技術総合研究所, 地質調査総合センター, 首席研究員 (80357194)
Project Period (FY)	2016-04-01 – 2019-03-31
Keywords	火山 / 固体地球物理学 / 地質学
Outline of Final Research Achievements	The island-forming eruption at Nishinoshima volcano, Ogasawara Islands, Japan, started in November, 2013, lasting until July, 2018. The total volume of erupted lava exceeded one hundred million cubic meter, which is a recent biggest eruption in Japan. We conducted several remote sensing observations, a landing survey in October 2016, various types of geophysical observations, such as ocean bottom seismic and geomagnetic observations, seismic-acoustic observation in Nishinoshima, and operated a remote-island volcano monitoring system. This survey reveals the long-term eruption activity and the magma ascending process just before the eruption. The magma temperature was relatively higher than that of an ordinary island arc magma and the composition was a crystal-poor. The variation of magma composition suggests that andesite magma derived from a crystal-rich shallow reservoir and a crystal-poor deeper reservoir.
Free Research Field	固体地球物理学
Academic Significance and Societal Importance of the Research Achievements	西之島の火山島形成プロセス，特にその噴火に至るマグマ上昇過程やマグマ供給システムの一端を，地球物理学的観測と物質科学的調査により明らかにしたことは，新たな火山島形成が世界的に見ても希な現象である事からも，学術的に高い意義を持っている．さらに，本研究において，Wave Gliderを用いた離島火山モニタリングシステム及び遠隔離島地震・空振観測装置が有効である事を示した事は，今後の海洋島の火山活動監視に新たな有力な観測手段を提供したものであり，火山防災上も意義の高い成果である．