Abstract: The origin and distribution of induced earthquakes,associated with the impoundment of the Xinfengjiang reservoir depend not only on the local tectonic environment but also on the additional stress state which is caused by the water loading strain.Therefore,reservoir induced earthquakes tended to be concentrated on the margin of the lake and occurred in two iayers according to the focal depth,between which is a rare-earthquake layer.The frequency of the shallow events has a correlation to the water level of the lake. On the contrary,the earthquakes in the deep layer occurred more often during offset of the lake. In the Xinfengjiang area there are two kinds of seismic faults. Both of them obviously are high angle active faults,which play a much more important role than low angle faults in occurrence of the reservoir induced earthquakes.By means of mathematical simulation to restore the earthquake sequences of this area after impoundment of the lake,it is sure that in the case of certain tectonic stress field,the high angle faults perpendicular to the additional tension stress are more unstable than the others. The calculations also indicate that the seismic events caused by the given geological model in the presence of the stress field with the maximal stress axes striking N30癢,the minimal stress axes striking N30癊 and the moderate stress axes vertical fit in with,the actual earthquakes. The stress fields derived from the calculations are similar to those obtained by other means. Mathematical simulation demonstrats that the NNW-trending fault belt generating the main shock (M=6.1) is the least stale. The seismogenic structures of main shock and two after-shocks with a magnitude greater than 5 belong to the same fault. After the main shock,the stress states for rock changed,and the NNE and ENE faults are less stable.

摘要： 本文在地质考察的基础上,采用数学模拟方法,重演了本区的地震序列,论证了诱发地震的构造条件。指出,新丰江水库有两组发震构造,它们的活动强度和时间有所不同。诱发地震的发震构造与水库蓄水前构造地震的发震构造属于相同构造体系,唯发震部位更逼近水库。文章还指出,库基弹性变形引起的附加引张应变使部分地区的活动断裂更易于错动。水库荷载还使地震在剖面上有浅层和深层之分。它们的频度与水库水位有不同的相关性。