大震前地下水位异常与应力异常区

利用井口水位对潮汐应力的响应，分析了含水层对强震孕育过程中应力变化的响应。结果显示，当含水层的瞬时应力变化值大于临界值时，水位的异常图像为阶变形态；当含水层的瞬时应力变化值小于临界值，但某一时段的累计值大于临界值时，水位的异常图像为缓变形态。而水位异常图像出现的上升或下降形态，取决于井孔含水层系统在大震孕育过程的应力调整再积累阶段所处的构造部位。水位震前异常的特征，源于地震孕育过程中应力异常区的形成。

Pre-earthquake anomaly ofgroundwater level and anomalous stress region

Based on the response of well water level to tide stress, the authors analyzed the response of well aquifer to stress variation during the process of earthquake preparation. While the instantaneous stress variation of aquifer is more than the critical value, the change pattern of water level anomaly is leap. If the instantaneous stress variation of aquifer is less than the critical value, but accumulation of stress variation of aquifer is more than the critical value in the course of time, water level anomaly is gentle. However, decline or rise of water level anomaly depends on the tectonic position where the well aquifer lies in the process of stress regulation and re accumulation. That is to say, the feature of water level anomaly before strong earthquake is resulted from the region where stress anomaly was formed during the process of earthquake preparation.