Dynamic rheology measurements of bubble and crystal bearing magmas

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H04042
• 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: Hiroshima University
• Principal Investigator: Namiki Atsuko 広島大学, 総合科学研究科, 准教授 (20450653)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: マグマ / 粘弾性 / 気泡

Outline of Final Research Achievements

We measured the rheology of high porosity rhyolitic magma at high temperatures. The measured shear modulus and strength are several orders of magnitude lower than bubble-free rhyolite melt, implying that high porosity magma cannot avoid fracturing during magma ascent. The occurrence of fractures is observed in the temperature range of low attenuation. Our measurements also show that the shear modulus becomes lower by increasing porosity, which can slow the shear wave velocity. These results suggest that knowing the attenuation of the seismic wave is useful to evaluate magma temperature and the possibility of a fragmentation event that may determine subsequent volcanic activities.

Free Research Field

火山学

Academic Significance and Societal Importance of the Research Achievements

本研究により得られた最も重要な成果は、マグマのＱが温度に依存する事、剛性率が気泡含有量に寄る事である。Ｑは地震波の減衰で見積もる事ができ、また、剛性率は地震のＳ波伝播速度を変える。この結果は地震観測を用いて噴火前のマグマの温度と気泡含有量を推測できる可能性を示している。その実現の為には、より広いパラメータ範囲における精度の高いマグマの粘弾性測定が必要である。