Study on fluid injection beneath the volcanic lake at the Nakadake 1st crater of Aso Volcano - aiming to understand future phreatic explosions

2015 Fiscal Year Final Research Report

• Project/Area Number: 25870352
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Natural disaster / Disaster prevention science; Solid earth and planetary physics
• Research Institution: Kyoto University
• Principal Investigator: Akihiko Yokoo 京都大学, 理学(系)研究科(研究院), 助教 (70420403)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: 阿蘇火山 / 中岳第一火口 / 湯だまり / 土砂噴出 / 水蒸気爆発 / 火山噴火

Outline of Final Research Achievements

Volcanic activity of the Nakadake 1st crater of Aso volcano has increased since 2013 immediately after this project was started. Volcanic lake at the crater has been disappeared and then new active vent was opened inside the crater in January 2014. On 25 November 2014, magmatic eruptions started after c.a. 20 years dormancy. So as to satisfy an extreme objective of this project - understanding and evaluating of future phreatic explosions - several kinds of analysis on seismo-acoustic signals were investigated. From the analysis of high-frequency continuous tremor, final section of the pathway of volcanic fluids toward crater bottom was revealed. Monochromatic infrasound tremor with the ~0.5 Hz peak was identified by a new network of infrasound sensors. Source process of this signal was considered as the Helmholtz resonance inside the conduit.

Free Research Field

火山物理学