利用衰减结构层析成像方法尝试对紫坪铺水库区域地壳Qs进行成像,获得该区浅层地壳静态及蓄水前、后的Qs变化特征,结合实验研究成果、岩体岩性、断裂构造、水文地质条件探讨库水的渗透作用及其对地壳介质的影响,对研究区内地震活动类型及发震成因的介质物性变化进行了讨论.研究结果表明:紫坪铺水库区域地壳Qs横向不均匀变化显著,库区周边近似存在低Qs值环形区域,主要包括水库东北、东南、西南、西北及库区中段五个区域.其中,水库东北、库区中段、西南低Qs区域与库水渗透关系密切,初步认为库水可能沿着通济场断裂中段和两端的岩石破碎带及节理、裂隙发育地区向地下渗透,使岩石孔隙中充满流体,内摩擦增大,地震波大大衰减,从而导致Qs值大幅下降.同时,在西南区诱发了水库小震群,在东北区和东南区诱发了部分水库小震群.另外,紫坪铺水库区域东北、东南、西南三个小震群基本位于高Qs值(低衰减)和低Qs值(高衰减)过渡区域,可能由于低Qs区地震波衰减大,不易积累能量,而高、低Qs值的过渡区域,介质介于“软”、“硬”之间,有可能积累应变能,孕育地震.当高、低Qs过渡区域岩石裂纹饱含水或部分含水后,水对裂纹边界起潮湿和润滑作用,降低了发震断层的抗剪强度,使滑动容易产生,从而诱发地震. Attenuated structure tomography imaging method is used to image the Qs of the Zipingpu reservoir, and the static characteristics of the shallow crust and the Qs variation before and after water storage are obtained. Based on the experimental results, lithology, fault structure, Hydrogeological conditions of the reservoir water infiltration and its impact on the crustal medium, the study area of ​​seismic activity types and the cause of the media changes in the physical properties are discussed.The results show that: the Zipingpu reservoirs regional crustal uneven Qs There are five areas around the reservoir in the northeast, southeast, southwest, northwest and middle of the reservoir area. Among them, the relationship between reservoir QS and reservoir water infiltration in northeast reservoir, middle reservoir area and southwest low Qs area It is preliminarily believed that the reservoir water may penetrate into the rock along the rock fragments and joints at the middle and both ends of the Tongji fault and the fractured areas. The rock pores are filled with fluid, the internal friction increases, and the seismic waves greatly attenuate, resulting in the Qs value A large number of reservoirs were evoked in the northeast area and the southeast area.In addition, the reservoir area of ​​Zipingpu Reservoir The three small earthquakes in the northeast, southeast and southwest of China are basically located in transitional areas with high Qs (low attenuation) and low Qs (high attenuation), which may be due to the large attenuation of the seismic wave in the low Qs area and the high and low Qs Of the transitional zone between the “soft” and “hard” media, it is possible to accumulate strain energy and produce earthquakes.When the rock cracks in the high and low Qs transitional areas are full or partly water-saturated, Moisture and lubrication play a role, reducing the shear strength of seismogenic faults, so easy to produce slip, thus inducing earthquakes.