Abstract:After a large earthquake took place, the accumulated stress and strain in focus and its neigborhood was released quite fully, so that the parallel faults in a certain range couldn't accumulate enough stress and strain to result in a large earthquake for some time. It means that a large earthquake has an effect of reducing seismic risk of in some distance for some time. So it is important to determine the distance and buration of reducing seismic risk. This paper, on the basis of the large earthquakes occurred in mainland of China, calculated the earthquake intervals for different length of time, From these statistial data the dominant interval and the optimal distance of reducing seismic risk were got. The dominant interval and the optimal distance of reducing seismic risk are inversely proportional to length of time. The distribution of earthquake intervals can be simulated by a normal probability function. Besides, the ground displacement at the distance of reducing seismic risk was given by the elastic dislocation theory.
