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ID 51064
creator
Tanaka, Yukie
Okumura, Satoshi
Sasaki, Osamu
Sano, Kyohei
Takeuchi, Shingo
subject
Magma
Fracture
Rheology
Bubble
abstract
The rheology and strength of bubbly magma govern eruption dynamics by determining the possibility of fragmentation of ascending magmas. They are also required parameters for understanding seismic monitoring. We measured the rheology and strength of high porosity rhyolitic magma at 500–950 °C. 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 low-temperature magma (≤800 °C). In this temperature range, the measured attenuation is low. That is, the elastic energy originated by deformations avoids attenuation and is stored in the bubbly magma until released by fracturing (Q > 1). The newly found porosity-dependent strength based on our measurements comprehensively explains three different fragmentation criteria that have been previously proposed independently. 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.
description
This work is supported by JSPS KAKENHI grants 16H04042 and 19H00721.
journal title
Journal of Volcanology and Geothermal Research
volume
Volume 392
start page
106760
date of issued
2020-02-15
publisher
Elsevier
issn
0377-0273
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
© 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
This is not the published version. Please cite only the published version. この論文は出版社版ではありません。引用の際には出版社版をご確認、ご利用ください。
relation url
department
Graduate School of Advanced Science and Engineering
note
The full-text file will be made open to the public on 15 Feb 2022 in accordance with publisher's 'Terms and Conditions for Self-Archiving'