2002年3月3日大桥水库诱发了MS4.6级水库地震,其发震构造是安宁河东支断裂近傍具有正断层性质的一个分支断裂。据大桥台网7年多库区地震观测事件记录,地震空间分布上水体附近有一个明显的活跃过程,大坝上游发生小震群,大坝下游发生主震序列。地震的震源深度在蓄水前后有明显变化。4.6级地震的震源机制解的主压应力轴方位和倾角与大多数活动断裂上的地震有明显的差别,主压应力轴的倾角与其它的水库地震相比也存在较大差别。 On March 3, 2002, the Daqiao Reservoir induced the MS4.6 reservoir earthquake. Its seismogenic structure is a branch fault with normal fault near the East Branch of the Anning River. According to the record of seismic observation of Duku area in Bridge network for more than seven years, there is an obvious active process near the water bodies in the spatial distribution of the earthquake. Small earthquakes occur upstream of the dam and mainshock sequences occur downstream of the dam. The focal depth of the earthquake changed significantly before and after water storage. The azimuths and dip angles of the principal compressive stress axes of the focal mechanism solution of the M 4.6 earthquake are obviously different from those of the most active faults. The dip of the main compressive stress axis is also greatly different from other reservoir earthquakes.