关键词: 声发射, 地震平静, 新生断层, 断层蠕滑

Abstract: This paper discusses the mechanism for seismic quiescence before large earthquakes based on experimental results of acoustic emission during rock deformation. Under the condition of biaxial compression and constant loading point velocity,samples simulating discontinuous faults,including compressional en-echelon faults,fault with macro-asperity,and model-Ⅲ shear fault,show relative quiescence of acoustic emission before slip instability,which is characterized by obvious decrease of occurrence rate and release of strain energy of acoustic emission events. The analysis indicates that the predominant deformation mode during this stage is creep sliding along fault zone,especially along the newborn fault segment in the discontinuous area,causing decrease of differential stress in the sample. The reason for occurrence of this stage is that a relatively uniform distribution of resistance along a fault zone is necessary for its slip instability,but uneven surface of newborn fault segment does not meet this condition,so the creep sliding is needed for resistance uniformization along the fault zone. Because there exist only very small asperities along the fault zone and the stress relaxation occurs in the whole sample during this stage,acoustic emission activity becomes weak. Based on the experimental results,it is suggested that the process of creep sliding and resistance-uniformization along fault zone is one possible mechanism for seismic quiescence before large earthquake.

Key words: acoustic emission, seismic quiescence, newborn fault, creep sliding