汶川大地震前地震频度变化和小震群活动

Seismic rate and small seismic swarm changes before the 2008 Wenchuan M8.0 Earthquake

分析后认为,从1999年开始龙门山断裂带上地震活动增强,并持续到2008年5月12日汶川8级地震发生前一个多月。地震活动的增强主要以最大地震的震级为3、4级的小震群活动的方式表现。2006年至2008年3月间,有两个小震群出现在汶川8.0大震震中附近。小震群地震震源机制的结果表明,随时间接近汶川8.0级大震发生,小震群的震源机制趋向一致,这些在空间分布不均匀的密集小破裂逐渐成定向有规律地排列,有利于裂隙的进一步扩展贯通,形成大破裂。

The index of seismic rate and small seismic swarm before the 2008 Wenchuan M8.0 Earthquake appeared a tendency of increasing since 1991 along the Longmenshan seismic faults and this tendency kept till the seismic event occurred.The intensity of small seismic swarms with magnitude from M3 to M4 increased.Between 2006 and 2008 there were two small seismic swarms that occurred near the epicenter of the 2008 Wenchuan M8.0 Earthquake.Before the 2008 Wenchuan M8.0 Earthquake the results of the earthquake mechanis...