Abstract: Based on the analyses of focal depth distribution in mainland China, we studied the physical features of the crustal media, especially the rheological features of the crustal rocks, and set up a related seismogenic model to reveal the earthquake development environment and explain the mechanism of focal depth distribution. Geothermal results are used to deduce the depth of the brittle-ductile transition zone in the crust of East China and West China, which shows that the depth is about 20～25km in East China and 35～45km in West China. The depths are respectively consistent to the lower limits of the focal depths in East China and West China, which indicates that the continental earthquakes in China terminate at the depth of the brittle-ductile transition zone. According to the deduced results, the brittle-ductile transition zone in the crust would control the distribution of focal depths. A focal model is developed to simulate the continental strong earthquakes, and to explain the mechanism and processes of earthquake development in continental areas.

Key words: Crustal media, rheology, focal depth, brittle-ductile transition zone, seismogenic model

摘要： 在分析归纳中国大陆地区地震震源深度分布特征的基础上,着重分析了地壳介质的物理性质,特别是地壳介质的流变特征,进而探讨了震源深度分布的物理解释和孕震环境.文中应用中国陆区地热研究中的有关成果,推导了中国东、西部地区壳内脆韧性转换带的深度,给出东部地区壳内脆韧性转换带深度为20～25km,西部地区为35～45km,这一结果显示出壳内脆韧性转换带与我国东、西部震源深度的下界面基本一致,且中国大陆地震的深度大体上终止于壳内脆韧性转换带.从而表明,壳内脆韧性转换带有可能是控制大陆地震震源深度分布的主要原因.在这些研究的基础上,建立了大陆强震的震源模型,讨论了大陆地震的孕震过程和有关机理问题.

关键词: 地壳介质, 流变性, 震源深度, 脆韧性转换带, 孕震模型