Abstract: The Three-Gorges well network is the first well network in China established specially for the purpose of monitoring the groundwater precursors of reservoir-induced earthquake. The basic consideration of the establishment of this well network is based on the fact that the seismic event of certain magnitude induced by the storage of reservoir may cause the changes of stress and strain states of the aquifer, as well as the corresponding pore water pressures. The number and spacing of the wells are determined according to the magnitude of earthquake(M_S), the length of seismogenic fault(L)and the variation range of stress strain field(R). The selection of well locations is based on the groundwater behaviors sensitive to earthquakes. Such peculiar tectonic sites as the termination, inflection and junction of fault zones are selected for well location. The depth and structure of the wells are decided according to the requirement that the well may reveal well enclosed confined aquifer and minimize the influence of surface water and hydro atmospheric factors on the premise of limit funds. According to the afore mentioned considerations, 4 wells are drilled at the dam site and 4 wells at the head of the Three-Gorges Reservoir. The depths of the wells are between 100～ 200m, and all the wells expose well enclosed confined aquifer. Primary observations show that the arrangement of the Three-Gorges well network and the establishment of the observation wells are relatively successful. They form a good base for monitoring the precursor of reservoir-induced earthquake.

Key words: well network arrangement, observation well, ground water behavior, Three-Gorges area

摘要： 介绍了我国第1个以监测水库诱发地震的地下水前兆为目标的三峡井网布设与观测井建设的科学思路及其实施结果.由于水库蓄水引发一定震级的诱发地震时,会引起含水层应力应变状态及与其相关的孔隙压力变化,并导致观测井水位的异常变化,为此利用震级(M_S)、孕震断层长度(L)与应力应变场变化范围(R)的关系确定了井数与井间距;井位的选择,主要依据了地下水动态为映震灵敏条件的科学认识,选择了断裂带及其应力易集中的端点、拐点与交点等特殊构造部位;井深与井孔结构的确定,遵循了在有限投资的前提下,尽可能揭露封闭性好的承压含水层(带)和尽可能减少地表水文气象因素干扰的原则.按照上述思想与原理,在坝区和库首区各布设了4口井,井深为100～200m,均揭露出封闭性较好的承压含水层(带).初步观测结果表明,三峡井网的布设与观测井的建设较为成功,为诱发地震前兆监测奠定了良好的基础.

关键词: 井网, 地下水动态, 三峡