Friction falls towards zero in quartz rock as slip velocity approaches seismic rates

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234

作者：

GD Toro，DL Goldsby，TE Tullis

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摘要：

An important unsolved problem in earthquake mechanics is to determine the resistance to slip on faults in the Earth's crust during earthquakes. Knowledge of coseismic slip resistance is critical for understanding the magnitude of shear-stress reduction and hence the near-fault acceleration that can occur during earthquakes, which affects the amount of damage that earthquakes are capable of causing. In particular, a long-unresolved problem is the apparently low strength of major faults, which may be caused by low coseismic frictional resistance. The frictional properties of rocks at slip velocities up to 3 mm s(-1) and for slip displacements characteristic of large earthquakes have been recently simulated under laboratory conditions. Here we report data on quartz rocks that indicate an extraordinary progressive decrease in frictional resistance with increasing slip velocity above 1 mm s(-1). This reduction extrapolates to zero friction at seismic slip rates of approximately 1 m s(-1), and appears to be due to the formation of a thin layer of silica gel on the fault surface: it may explain the low strength of major faults during earthquakes.

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关键词：

Experimental/ earthquakes faulting friction quartz rocks/ frictional resistance frictional properties rocks slip velocities seismic slip rates silica gel layer formation fault surface major faults earthquake mechanics Earth crust coseismic slip resistance shear-stress reduction slip displacements large earthquakes quartz rocks 3 mm/s/ A9160B Mechanical and acoustic properties of rocks, minerals and soil A9130B Seismic sources A9145B Sub-plate scale tectonics (faults, folds, rifts, etc.)/ velocity 3.0E-03 m/s