Abstract: 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.

Key words: seismicity, earthquake clustering, moderate earthquake growth rate

摘要： 通过对中国大陆及邻区4个Ⅰ级活动地块中1972-2003年全部地震资料的系统分析,认为强震中期阶段典型的地震活动演化图像是中等地震聚集活动,震前震中区附近的地震密度和有效速率增高。文中用中等地震增长率来刻划强震孕育过程中中等地震活动的加速增长,结果表明:中等地震聚集活动密度的增长率能够较好地反映强震前中期异常变化特征,对各活动地块的分析表明华北地块中等地震增长率达到180%以上时,未来1～3a中等地震异常聚集区及其附近会发生强震;而西域、青藏和滇缅地块中等地震增长率达到250%以上时,应注意中等地震异常聚集区及其附近强震的发生。因此,中等地震增长率可以作为中期预报的定量化指标。

关键词: 地震活动性, 聚集活动, 中等地震增长率