Abstract: Accurate earthquake location is of primary importance in studying the seismicity of reservoir area. The well known program Velest was used to inverse the minimum 1-D velocity,hypocenter location and station correction simultaneously.We selected 529 earthquakes,which were recorded at least by 10 stations each and whose max azimuth gap was less than 180?,to re-determine the velocity model and station corrections with three different initial models used by different researchers before.Using the 1-D minimum velocity model and station correction,we relocated 2138 earthquakes in the Three Gorges area.The average focal depth changes remarkably in different areas,as 5.6km in the area near Xiannvshan Fault,2.9km in the Xietan area and 2.6km in the Badong area.Divided by the depth of 5km,the b values are different,as 1.07,1.16 and 0.90 for all,shallower and deeper events respectively. The frequency of shallower or deeper events per 15 days increases with impounding.But that of the shallower ones drops quickly and the deeper attenuates slowly when water lever keeps stable.

Key words: earthquake location, Three Gorges Reservoir, seismicity

摘要： 在已有速度模型的基础上,选取三峡水库区529个地震重新确定了速度模型和台站校正,并利用该结果对2 138次地震进行了定位。研究表明,在不同区域震源深度存在明显的差异,仙女山断裂附近的地震平均震源深度为5.6km,而巴东地区的地震平均震源深度为2.6km。以震源深度5km为界,浅于5km的地震的b值为1.16,而深于5km地震的b值为0.90,不同深度地震的频次变化与水位关系差异明显。

关键词: 地震定位, 三峡水库, 地震活动