滇西南地区地震活动特征分析

摘要

Using theMS≥5 earthquakes since recorded earthquakes and small earthquakes catalogs since 1965, the time, space and magnitude distribution characteristics of earthquakes as well as small, medium earthquake activity before the great extent earthquake in southwest of Yunnan Province are analyzed. The characteristics of seismic activity of different sections and magnitude earthquakes are also studied. It is discovered that 5 magnitude earthquakes concentrated in the main faults, the average time interval of the two earthquakes was 558 days (about 1.5 years). The duration of seismic quiet time is generally 30 months or so. TheMS≥6 earthquakes mainly concentrated in the nearby intersection of NW trending fault and NE trending fault. On the time scale, there are obvious features of quiet and active alternation. The average duration of each period of quiet and active period is about 15 years. In addition, there are clear pre-release phenomenon and directional migration of small and medium earthquakes before most of the strong earthquakes.%选取有地震记载以来的MS≥5地震与1965年以来的小震目录，分析滇西南地区地震的时、空、强分布特征及强震前中小震活动，开展分段、不同震级地震活动特征研究，发现：滇西南地区5级地震集中分布在主要深大断裂带上，时间分布呈现丛集特征，两次地震发生时间间隔平均为558天（约1.5年），地震平静时间一般持续约30个月；MS≥6强地震主要集中发生在北西向断裂与北东向断裂交汇部位附近，在时间尺度上存在明显的平静和活跃交替特征，每个平静期和活跃期平均持续约15年，且大部分强震前存在清楚的预释放现象和中小地震加速定向迁移特征。