云南M≥5地震震前异常的统计特征

Statistical Characteristics of the Anomalies before the M≥5 Earthquakes in Yunnan Region

通过对1970年以来云南38组M≥5地震震前异常的综合分析,得到云南5级以上地震的异常共性特征:震前小震频度普遍增强;6级以上地震的异常持续时间比5级地震长;异常分布越广可能未来地震的震级越大;部分前兆观测项目趋势异常结束、新的突变异常增多,是地震孕育进入短临阶段的标志。

We synthetically analyzed the anomalies before the 38 groups of earthquakes （M≥5） since 1970 in the Yunnan region, and obtained the common characteristics of the anomalies. The frequency of small earthquakes usually increases before the earthquakes （ M I〉 5 ） ; the durations of anomalies of M ≥ 6 earthquakes are longer than those of M5-6 earthquakes; the wider the anomalies distribute, the bigger the magnitude of the earthquake （M≥5） ; the ending of some tendentious precursory anomalies and the increasing of new abrupt anomalies can be considered as the sign of the earthquake preparation going into short-term and impending-earthquake period.