关键词: 震级频度关系, b值, 声发射, 破裂, 失稳滑动

Abstract: By the spatial scanning of the frequency-magnitude distribution of earthquakes in Beijing-Tianjin-Tangshan-Zhangjiakou area,it is found that there are three types of the distribution of earthquakes in this area. Type Ⅰ is consistant with a linear b-value model and types Ⅱ and Ⅲ are consistant with a characteristic earthquake model. The area,in which large earthquakes have never occurred in last 22 years,often has a distribution of type Ⅰ,and the area,in which large earthquakes have occurred,often has a distribution of type Ⅱ and Ⅲ. Result of the rock mechanical experiments shows that the frequency-magnitude distribution of acoustic emission events in rocks has a high b-value in the process of fracturing and fracture joining,and has a lower b-value in the process of frictional slip accompanied with stick-slip. But the frequency-magnitude distribution in a whole process of rupturing and slipping of intact rocks is consistant with the characteristic earthquake model. Therefore,it is evident that the frequency-magnitude relationship may represent a stage of structural deformation for an area. The nonlinearity of frequency-magnitude distribution might give us more information about the geometrical characteristics of the rigional structure. The emergence of nonlinearity of F-M distribution in area with moderate magnitudes but without large magnitudes in the considered period may indicate that the area is in a state much closer to the critical point for the unstable sliding.

Key words: Frequency-magnitude distribution, b-value, Acoustic emission, Fracture, Unstable slidin, Beijing-Tiagnjin-Tangshan-Zhangjiakou area