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

• 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
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥18,070,000 (Direct Cost: ¥13,900,000、Indirect Cost: ¥4,170,000); Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2018: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000); Fiscal Year 2017: ¥13,780,000 (Direct Cost: ¥10,600,000、Indirect Cost: ¥3,180,000)
• Keywords: 火山ガス / 噴火 / 火山 / 火山ガス組成

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.

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。

Research Products

• [Journal Article] 火山ガス観測から推定される火山活動推移過程 (2019)
  • Author(s): 篠原 宏志
  • Journal Title: 火山 Volume: 64 Pages: 121-129
  • NAID: 130007676214
  • Peer Reviewed
• [Journal Article] Salt shell fallout during the ash eruption at the Nakadake crater, Aso volcano, Japan: evidence of an underground hydrothermal system surrounding the erupting vent (2018)
  • Author(s): Shinohara Hiroshi、Geshi Nobuo、Yokoo Akihiko、Ohkura Takahiro、Terada Akihiko
  • Journal Title: Earth, Planets and Space Volume: 70 Issue: 1 Pages: 1-10
  • DOI: 10.1186/s40623-018-0798-4
  • NAID: 120006517893
  • Peer Reviewed / Open Access
• [Journal Article] Variation of volcanic gas composition during the eruptive period in 2014?2015 at Nakadake crater, Aso volcano, Japan (2018)
  • Author(s): Shinohara Hiroshi、Yokoo Akihiko、Kazahaya Ryunosuke
  • Journal Title: Earth, Planets and Space Volume: 70 Issue: 1 Pages: 1-21
  • DOI: 10.1186/s40623-018-0919-0
  • Peer Reviewed / Open Access
• [Presentation] Comparison of persistent degassing activities of basaltic and silicic volcanoes (2019)
  • Author(s): Shinohara H
  • Organizer: IUGG General Assembly
  • Int'l Joint Research
• [Presentation] 阿蘇中岳の火山ガス組成変化とマグマ-熱水系相互作用 (2017)
  • Author(s): 篠原宏志・風早竜之介・下司信夫、横尾亮彦・大倉敬宏、 寺田暁彦
  • Organizer: 日本火山学会秋季大会
• [Presentation] VARIATION OF VOLCANIC GAS COMPOSITION AND MAGMA-HYDROTHERMAL INTERACTION AT NAKADAKE CRATER, ASO VOLCANO, JAPAN (2017)
  • Author(s): Shinohara H, Geshi N, Yokoo A, Ohkura T, Terada A.
  • Organizer: CCVG Workshop
  • Int'l Joint Research