珊溪水库地区三维构造特征与深部水库诱发地震环境研究

利用大地电磁测深法首次在珊溪水库地区开展三维地震深部构造特征探测，获得该地区70 km²面积的三维电性结构，建立该区域深部三维地质构造模型，探讨水库地震发生的深部构造环境。结果表明：1）珊溪水库地下存在以双溪-焦溪垟断裂为主的3条断裂组成的向西南侧伏的三角形断块，2.5级以上地震基本发生在该特殊构造内。2）水库深部存在3个主要的“低阻通道”，地震活动集中在中部_f11-3“低阻通道”沿线，随着地下水沿f_11-3流体通道自东南向西北渗透，地震活动也沿该方向呈现阶段性迁移。3）水库东侧温州-泰顺断层及花岗岩阻隔双溪-焦溪垟断裂向东发展，造成地应力无法向东传播，可能是该断层以东无地震发生的主要原因。

Research on the Three-Dimensional Structural Characteristics and Deep Reservoir-Induced Seismic Environment in Shanxi Reservoir Area

Using the magnetotelluric sounding method, we explore the 3D seismic deep structural characteristics in Shanxi reservoir area for the first time and obtain the 3D electrical structure of 70 km². Then we establish the 3D geological structure model in this area and discuss the deep structural environment of reservoir-induced earthquakes. The results show: 1) In Shanxi reservoir area, there is a triangular fault block trending to south-west which is mainly composed of three faults, the Shuangxi-Jiaoxiyang faults is the principal of the three faults, and almost all earthquakes with magnitude greater than 2.5 basically occurred in this special structure area. 2) There are three main low-resistance channels in the deep part. Seismic activity is concentrated along the middle f_11-3 low-resistance channel. With groundwater permeating from southeast to northwest along the f_11-3 fluid channel, seismic activity also migrates periodically along this direction. 3) Wenzhou-Taishun fault and granite in the east block the eastward development of Shuangxi-Jiaoxiyang fault, resulting in the inability of in-situ stress to propagate eastward, which may be the main reason for the absence of earthquakes to the east of the fault.