2021年5月21日漾濞MS 6.4地震前地震活动异常分析

2021年5月21日漾濞发生M_S 6.4地震，震前地震活动异常明显，中长期阶段云南地区3级地震活动水平较低，滇西北地区出现长达456天的4级地震平静；短临阶段震中区附近出现3—4级地震条带；临震阶段中小地震活动由外围地区开始向震中区迁移，震中区出现直接前震。

Analysis of the seismicity anomalies before Yangbi Ms 6.4 earthquake on 21 May 2021

An M_S 6.4 earthquake occurred in Yangbi, Yunnan on May 21, 2021. The seismicity anomaly characteristics were obvious before the earthquake. For the medium- and long-term anomalies, the activity of the earthquake of magnitude 3 in Yunnan was at a relatively low level and the earthquake quiescence of magnitude 4 in Northwest Yunnan lasted 456 days. A seismic belt of M 3-4 earthquakes formed quickly in the short-term and impending stage. Small and medium earthquakes began to migrate from the peripheral area to the source area and direct foreshocks occurred in the source area in the impending stage. Some of the seismic activity anomalies that occurred before the earthquake provide a good basis for us to determine the time and place of short-term prediction.