江苏常熟—太仓5．1级地震的前兆异常及可能的前兆机制

Precursors Anonaly and Probable Precursor Pattern to Changsu-Taicang Ms5.1 Earthquake

这次地震前震中附近地区的地震活动随时间呈波浪式起伏，形成了小震条带，出现了小震群；地下水（水位、水温）异常非常强烈；地形变异常也观测到了。分析发现：前兆不是沿断裂带分布，而主要是于近震中（≤５０ｋｍ）的破裂面法线方向；似可用ＩＰＥ模式解释一些前兆现象。地震前兆的空间分布对未来震中的预报是很有意义的。震前半小时发生的，位于震中地区上中天的月蚀或许触发了这次地震。必须指出的是本文所采用的异常都是在震前发现的。

The seismicity map of 1990 Changsu-Taicang Ms5. 1 earthquake shows an undulation,belt and small groups forms. Groundwater anomalies are located almost along the normsl direction of rupture plane instead of direction of fracture zone. These anomalies can be explained by the IPE modal. The space distribution characteristics of anomaly is important tothe research of earthquake prediction.The lunar eclipse occured over Changsu may be a trigger factor half hour before theearthquake.