Fragility and an extremely low shear modulus of high porosity silicic magma

Journal of Volcanology and Geothermal Research 392 巻 106760- 頁 2020-02-15 発行
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タイトル ( eng )
Fragility and an extremely low shear modulus of high porosity silicic magma
作成者
Tanaka Yukie
Okumura Satoshi
Sasaki Osamu
Sano Kyohei
Takeuchi Shingo
収録物名
Journal of Volcanology and Geothermal Research
392
開始ページ 106760
抄録
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.
著者キーワード
Magma
Fracture
Rheology
Bubble
内容記述
This work is supported by JSPS KAKENHI grants 16H04042 and 19H00721.
言語
英語
資源タイプ 学術雑誌論文
出版者
Elsevier
発行日 2020-02-15
権利情報
© 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。
出版タイプ Author’s Original(十分な品質であるとして、著者から正式な査読に提出される版)
アクセス権 オープンアクセス
収録物識別子
[ISSN] 0377-0273
[DOI] 10.1016/j.jvolgeores.2019.106760
[DOI] https://doi.org/10.1016/j.jvolgeores.2019.106760
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