eruptive activity evolution processes revealed from evaluation of magma degassing pressure variation

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H02955
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Shinohara Hiroshi 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)
• Co-Investigator(Kenkyū-buntansha): 森田 雅明 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, 研究員 (40805149) ; 風早 竜之介 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, 主任研究員 (50637379)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 火山ガス / 噴火 / 火山

Outline of Final Research Achievements

In order to understand degassing and eruption processes at frequently erupting volcanoes, we have developed methods for continuous monitoring and interpretation of gas compositions sensitive to changes in magma degassing pressure. Large changes in the SO2/H2S ratio in volcanic gas were observed along with eruptive activity changes at Sakurajima and during the 2014-2015 eruption of Aso volcano, and the ratio was considered as sensitive to the degassing pressure change. Especially at Aso volcano, the correlation also with the CO2/SO2 ratio variation was also observed, and was interpreted that the variation was caused by the bubbles rising from different depths in the conduit during the eruption.

Free Research Field

火山学

Academic Significance and Societal Importance of the Research Achievements

火山災害の軽減のためには、火山噴火の発生やその活動の変化に先立って起きる現象を把握することが必要である。本研究では火山噴火現象の推移や発生条件の変化を理解するために、噴火を繰り返す火山などで火山ガス組成変化の観測を行い、その変化原因を解析を行った。本研究では特にマグマの脱ガス圧力の変動に起因して生ずる火山ガス組成の変化に注目し、観測・解析を実施した結果、阿蘇や桜島の噴火活動期にはマグマ脱ガス圧力変動に起因すると考えられる、火山ガスのSO2/H2S比の大きな変動を検出した。