Abstract: This paper is concerned with the process of concentration and diffusion of the regional seismicity before and after eight great earthquakes (M_s=7.0),Xingtai,Bohai sea,Tonghai,Luhuo,Yongshan,Haicheng,Longling and Tangshan,which took place in China during 1966—1976. The process might be divided into three stages: (1) seismicity was distributed mainly in the far-source area; (2) then it migrated and concentrated in the focal region and near-source area; (3) after the occurrence of great earthquake,seismicity diffused toward the far-source area gradually Finally,Rice and Rudni-cki's inclusion model of earthquake precursor and the idea of stress adjustment are used to understand the above process.

摘要： 本文初步讨论了中国八次大地震(M_s≥7.0)前后区域地震活动的时空变化过程。在这些大地震前后区域地震活动可分为三个阶段:(Ⅰ)地震活动主要分布在远震源区内;(Ⅱ)活动迁移集中到震源区及近震源区内,接着,大地震发生;(Ⅲ)大地震发生之后,特别是早期强余震活动期过后,区域地震活动逐渐扩散到远震源区中去,扩散地点往往是(Ⅰ)阶段中不甚活动的地点。此外,(Ⅱ)阶段中区域地震活动的持续时间,以及(Ⅲ)阶段中地震活动开始向远震源区扩散的时间似乎和大震震级的大小无关。