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

摘要： 对京津唐张地区地震震级频度关系进行空间扫描后,发现该区的震级频度关系有三种类型:第1类符合线性b值模型,第Ⅱ、第Ⅲ类符合特征震级模型。近22年来未发生大震的地区往往属第1类。大震区往往属第Ⅱ、Ⅲ类。岩石力学实验结果表明,在岩石破裂及破裂连结过程中声发射事件的震级频度关系符合高b值线性模型。在岩石伴有粘滑的摩擦滑动过程中声发射事件的震级频度关系符合低b值线性模型。但是在一个完整岩石的破裂和失稳错动全过程中声发射事件震级频度关系符合特征震级模型。由此说明某一区域的震级频度关系可能反映了该区构造变形所处的阶段。一个地区震级频度关系上的多次转折可能包含了地区构造几何信息。一些未发生大震的地区,在中等震级段出现b值非线性现象,这可能意味着它更接近失稳前的临界状态。

关键词: 震级频度关系, b值, 声发射, 破裂, 失稳滑动