RELATIONSHIP BETWEEN REGIONAL SEISMIC ACTIVITY EVOLUTION AND ACTIVE BLOCK IN THE SEISMOGENIC PROCESS OF STRONG SHOCKS

Through systematic analysis of the whole seismic data in the 4 first class active blocks in Chinese continent and its neighbouring regions from 1972 to 2003, we get the typical mid-term seismicity evolution patterns of strong earthquake, i.e. the moderate-size earthquakes cluster and the earthquake density and specific rate increase in the future epicenter area prior to strong earthquake. This paper uses moderate earthquake growth rate to depict the acceleration growth of moderate earthquake activity in the seismogenic process of strong shocks,and the results show that the growth rate of moderate earthquake activity density can well reflect the anomaly variation character before strong shock. Analysis of each active crustal block indicates that when the moderate earthquake growth rate of the North China block is up to 180%, a strong shock will happen in the moderate earthquake anomaly concentration zone and its adjacent regions in the coming 1～3 years;and when the moderate earthquake growth rate of the West reaches 250%,we have to be alert to the occurrence of strong shock in the moderate earthquake anomaly concentration zone and its adjacent regions. Therefore,moderate earthquake growth rate can be used as a quantitative index of medium-term earthquake prediction.