Does seismic shaking enhance outgassing and decompressional vesiculation ? An experimental appoach

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03800
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Kanazawa University
• Principal Investigator: Sumita Ikuro 金沢大学, 地球社会基盤学系, 准教授 (90334747)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 地震 / マグマ / 結晶 / 粒子体積分率 / レオロジー / 空振 / 加速度 / 粒径

Outline of Final Research Achievements

We conducted experiments using suspensions (a model of crystal-bearing magma) on (i) outgassing, (ii) pore-pressure generation under shaking and obtained the following results. (i) We discovered that when the particle volumetric packing fraction (phi) is phi = 0.4 and the bubble volume is larger than critical, the bubble bursts as soon as it protrudes above the surface, and a resonance occurs in the bubble aperture. This phenomenon is interpreted as a consequence of bubble film being stretched faster than the critical velocity, such that the film failed brittly. (ii) We classified the resulting phenomena into 4 types, according to the style in which the pore-water pressure changes : no change, rise, fall, oscillation. We mapped the results as a function of shaking acceleration, particle packing fraction and particle diameter, and provided a physical explanation for the results.

Free Research Field

固体地球物理学

Academic Significance and Societal Importance of the Research Achievements

マグマはしばしば結晶（粒子）を含む。粒子の体積分率φが増えると(a) 流体的な性質から固体的な性質へと変わり、(b)間隙流体圧が上昇する場合から低下する場合へと変わる。これらの現象は火山噴火の様式に関係すると考えられているが、その詳細は分かっていない。本研究では(a)についてφ、気泡体積が変わると破裂の仕方、空振波形が顕著に変わることを発見した。この結果は空振からφ、気泡体積が制約でき得ることを示す。(b)については間隙流体圧の変化の様式をφ、振動加速度、粒径の関数として整理した。これは間隙水圧の指標となる地下水位の変化から、未知パラメータを制約する上で基礎となる。