关键词: 发震断层, 异常识别, 空间分布特征, 应力场, 数字模拟

Abstract: The anomalies are caused by the propagation or weakening of fault segments in short-termto imminent stages before an earthquake. The results of experiments and numerical simulationhave shown that the disturbant stress field accompanying by the short-term to imminant stage is afour-quadrant pattern for mean stress and an eight-petaline pattern for maximum shear stress.Inorder to judge the applicability of the mentioned patterns,a series of numerical models have beenstudied.It is found that no matter how complicated the fault system and the stress field are,thedisturbant stress field,basically,keeps the patterns,if the propagation or weakening has oc-curred along a fault.This result provides us a basis to distinguish the possibly coming instablefault.Meanwhile,the distortion of the disturbant stress field in complicated tectonic settingshould not be neglected.

Key words: Seismogenic fault, Anomaly recognition, Spatial distribution chacteristic, Stress field.Numerical simulation