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Journal: Journal of Geophysical Research  2016 No.7  Share to Sinaweibo  Share to QQweibo  Share to Facebook  Share to Twitter    clicks:678   
Title:
High-velocity frictional strength of Longmenshan fault gouge and its comparison with an estimate of friction from the temperature anomaly in WFSD-1 drill hole
Author: Tetsuhiro Togo, Lu Yao, Shengli Ma, Toshihiko Shimamoto
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Abstract:

This paper addresses the issue of whether high-velocity friction experiments yield frictional strengths of fault materials that are consistent with the level of friction estimated from the postseismic temperature anomaly measured across a coseismic fault zone. Experiments were conducted on gouge (composed of quartz, dolomite, illite, albite, and other clay minerals), collected from a large outcrop of the Yingxiu-Beichuan fault zone and from Wenchuan Earthquake Fault Scientific Drilling project hole-1 drill cores in Hongkou, Sichuan Province, China. This fault is a major fault of the Longmenshan fault system that caused the 2008 Mw7.9 Wenchuan earthquake. All experiments revealed dramatic weakening at high velocities with peak friction coefficient μp of 0.07~0.35 and steady state friction coefficient μss of 0.02~0.15 for wet gouge, as compared with μp = 0.49~0.86 and μss = 0.12~0.21 for dry gouge. The average friction coefficients over a displacement of 5.5 m (coseismic displacement) extrapolated to the normal stress in the fault zones are 0.1~0.05 and 0.06~0.03 for dry and wet gouges, respectively. The average friction coefficients of dry and wet gouges are within the upper and lower bounds of friction coefficients estimated from the temperature profiles, and there are overall agreements between the two sets of data that are completely independent. Dry and wet gouges are characterized by highly sheared slip zones often forming overlapping slip-zone structures and by broad shear zones, respectively. Wet gouge textures are perhaps closer to those of natural fault zone, but repeated slip experiments are needed to determine the textural evolution of wet gouge.

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