华北地区成组地震前后的地电阻率异常特征

分析了自有地电阻率观测资料以来华北地区发生的三次成组地震前后的异常特征,其中包括1976年唐山地震组、1989年大同地震组和1998年张北地震组.结果发现(1)成组地震的地电阻率异常持续时间都比较长,主震发生后异常一般会继续下降或维持低值异常不恢复,整个成组地震的趋势背景非常清楚;(2)主震前异常台站范围比较广,异常台站数目比较多,后续地震的异常多集中在震源区;(3)成组地震结束后,异常一般都很快恢复.最后探讨了成组地震的地电阻率异常发展特征与孕震机理的关系.

Characteristics of anomaly for earth resistivity before and after an earthquake group in north china

The characteristics of anomalies for all the data of earth resistivity during the three earthquake groups occurred in North China (Tangshan group occurred in 1976, Datong group occurred in 1989, Zhangbei group occurred in 1998) are analyzed. The results show: (1) the duration of resistivity anomaly for earthquake group is relatively longer, and the anomaly curves usually keep decreasing continuously or staying at the low value after the main shock, which makes the tendency background very clear during the whole course. (2)The number of station that has anomaly is large and its distribution is wide before main shock. However, anomalies of aftershocks concentrate in focal region. (3) Anomalies recover very quickly after the earthquake group. The relationship between the development of anomaly and the mechanism of earthquake preparation is discussed at the end.