地震活动因子A值及其在华北地震中短期预报中的应用

综合考虑了地震活动时空强３ 个方面的震兆特征，定义了地震活动因子 Ａ值．使用１９７２ ～１９９６ 年华北地区地震资料进行空间扫描，研究中强以上地震前 Ａ 值的中短期异常变化特征．结果表明，在中短期阶段大多数地震前出现的 Ａ 值中期异常区面积明显缩小或消失，也有一些地震前１ ～３ 个月 Ａ 值异常区面积再次增大．还就用 Ａ 值进行地震中短期预报的有关问题进行了讨论

SEISMICITY FACTOR A-VALUE AND ITS APPLICATION IN MID-SHORT TERM EARTHQUAKE PREDICTION IN NORTHERN CHINA

The seismicity factor A-value is defined by synthesizing the seismicity precursors in time, space and magnitude. The seismicity data of moderate or small earthquakes during 1972~1996 in northern China are used in spacial scanning of seismicity factor A-value, studying mid-short term change of the A-value before the earthquakes. The result shows that in mid-short term, the midterm anomaly zones of A-value that appeared about 2~3 years before a lot of strong earthquakes may contract or disappear obviously, and the zones may obviously extend again about 1~3 months before some earthquakes. Some problems about mid-short term earthquake prediction by using the A-value are also disscused.