日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS14] 地震発生の物理・断層のレオロジー

2019年5月29日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:岡崎 啓史(海洋研究開発機構)、向吉 秀樹(島根大学大学院総合理工学研究科地球資源環境学領域)、野田 博之(京都大学防災研究所)、吉田 圭佑(東北大学理学研究科附属地震噴火予知研究観測センター)

[SSS14-P03] 石英質岩石の中速摩擦強度の支配要因

*金川 久一1杉田 明日郁2高橋 美紀3澤井 みち代1 (1.千葉大学理学研究院、2.千葉大学理学部、3.産業技術総合研究所活断層・火山研究部門)

キーワード:めのう、シリカゲル、摩擦強度、中速

Frictional strength of quartz rocks is known to be extraordinary low at subseismic slip rates ranging from 1 mm/s to 10 cm/s, which has been ascribed to the hydration of comminuted amorphous silica, i.e., silica gel. In order to testify this hypothesis, we conducted rotary-shear friction experiments on intact agate or silica gel gouge at a normal stress of 1.5 MPa and slip rates (V) ranging from 1 mm/s to 10 cm/s. We also measured temperature (T) adjacent to the slip surface or the gouge layer during the experiments.

Steady-state friction coefficient of agate μss was ≈0.6 at V = 1 mm/s, ≈0.5 at V = 7 mm/s, and ≦0.1 at V = 10 cm/s. T was ≈25°C at V = 1 mm/s, ≈30°C at V = 7 mm/s, and up to 85°C at V = 10 cm/s, but the actual temperature along the slip surface must have been much higher. μss of silica gel gouge was ≈0.7 at V = 1 mm/s, 0.4–0.5 at V = 7 mm/s, and ≦0.2 at V = 10 cm/s. T was 25–28°C at V = 1 mm/s, 30–37°C atV = 7 mm/s, and 80–100°C at V = 10 cm/s, but again, the actual temperature in the gouge layer must have been much higher.

Thus our results show that agate or silica gel exhibits weakening with increasing T, and that the presence of silica gel does not reduce the frictional strength when T is not high enough. Shear strength of quartz rocks is high so that significant amount of frictional heat would be produced at asperity contacts even at V ≈ 1 cm/s, which must be responsible for weakening of quartz rocks at intermediate slip rates.