Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-SS Seismology

[S-SS14] Fault Rheology and Earthquake Physics

Wed. May 29, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Keishi Okazaki(Japan Agency for Marine-Earth Science and Technology), Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University), Hiroyuki Noda(Kyoto University, Disaster Prevention Research Institute), Keisuke Yoshida(Tohoku University)

[SSS14-P03] Mechanism controlling the frictional strength of quartz rocks at intermediate slip rates

*Kyuichi Kanagawa1, Asuka Sugita2, Miki Takahashi3, Michiyo Sawai1 (1.School of Science, Chiba University, 2.Faculty of Science, Chiba University, 3.Research Institute of Earthquake and Volcano Geology, Geological Survey of Japan)

Keywords:agate, silica gel, frictional strength, intermediate slip rates

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.