关键词: 摩擦, 粘滑, 高温高压, 地震, 孕震构造, 下地壳

Abstract: Mechanical behaviors of frictional sliding can be described well by rate-and state-dependent friction laws.This paper reviews factors that control sliding stability of crustal rocks,and summarizes as follows:(1)analysis of small perturbation around steady state sliding(linear analysis)shows that an important condition for self-sustained instability to occur is a negative rate dependence of friction(a-b<0).Under such a condition,earthquake slips can nucleate on active faults.(2)Measurement of water content in crustal rocks implies that both "dry" and "wet" conditions in the lower crust are possible,and previous creep experiments show that deformation mechanisms under dry conditions are notionally brittle fracture and faulting.(3)Attention has been paid to gabbro under high pressure and temperature as a number of strong earthquakes were discovered to have occurred in the lower crust.Experiments on dry gabbro indicate that velocity weakening may be the typical sliding behavior with temperature ranging from 420℃ to 615℃.Synthetically considering the relevant conditions such as "dry" condition that may exist in relatively cool interior of continental lower crust,and mafic rock that is not likely to deform by plastic flow under such conditions,we may extrapolate this result to actual tectonic settings where the environments are more complex.This may explain why earthquakes occur in the lower crust in some areas.

Key words: friction, stick-slip, high temperature and pressure, earthquake, seismotectonics, lower crust