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以相邻 2次地震的时间间隔作为统计量 ,对华北地区的地震活动异常平静进行了统计检验。统计结果表明 ,中小地震的时间间隔服从幂指数分布。对华北地区而言 ,中强地震之前大范围内中小地震活动的异常平静现象是明显的 ,以 90 %的置信概率认为 ,ML≥ 4 .5地震持续 110天以上的平静可判定为异常 ;约有 70 %的平静异常出现之后 ,华北地区有 MS≥ 5.0地震发生。
Taking the time interval of two adjacent earthquakes as the statistical data, statistical tests were conducted on the abnormal calm of seismic activity in North China. The statistical results show that the time interval of small and medium earthquakes obeys the power exponential distribution. For North China, the anomalous calm phenomenon of medium and small earthquakes within a large area before the moderate-strong earthquakes is obvious. With 90% confidence, it is considered that the quiescence of ML≥4.5 earthquakes lasting more than 110 days can be judged as abnormal. After 70% of calm abnormalities occurred, MS≥5.0 occurred in North China.