Structure and mass movement of hydrothermal system beneath volcanoes related with failed eruptions

2014 Fiscal Year Final Research Report

• Project/Area Number: 23310120
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Natural disaster science
• Research Institution: Kyoto University
• Principal Investigator: KAGIYAMA Tsuneomi 京都大学, 理学(系)研究科(研究院), 教授 (50126025)
• Co-Investigator(Kenkyū-buntansha): UTSUGI Mitsuru 京都大学, 大学院理学研究科, 助教 (10372559) ; OHSAWA Shinji 京都大学, 大学院理学研究科, 教授 (30243009)
• Co-Investigator(Renkei-kenkyūsha): KANDA Wataru 東京工業大学, 火山流体研究センター, 准教授 (00301755)
• Project Period (FY): 2011-04-01 – 2015-03-31
• Keywords: 火山 / 自然災害 / 地熱 / 地下構造 / 噴火予測

Outline of Final Research Achievements

This study proposes a new model for failed eruptions which decrease a reliability of prediction of volcanic eruptions. The authors carried out MT survey around typical volcanoes which have frequent failed eruptions. Beneath active craters, vapor-dominant hydrothermal fluids, supplied from a deeper part, are maintained in a relatively low resistivity region that is covered by a clay-rich cap, extremely low resistivity layer. Exsolved gases result in fumarolic areas, and mixing of gases with shallow groundwater forms hot springs around volcanoes. The authors developed a new method to estimate mass flux of volcanic gases from electrical conductivity distribution, and applied Unzen volcanic area. The estimated value is consistent with geochemical and geodetic observations. This suggests that volcanic gases are steadily released from magma into the overlying groundwater flow system, and that effective degassing may be one of the factors controlling failed eruptions.

Free Research Field

火山物理学