高邮-宝应M4.9级地震前周围水位的群体特征

高邮-宝应M4.9级地震是江苏陆地22年来发生的最大的地震。在震前2年发现省内流体井水位出现了群体性准同步变化,表现为震中区井水位的同步下降。本文重点分析了江苏省流体井水位变化特征,消除了气压、降雨和地下水开采的影响,用异常幅度与年变幅度比值、从属函数两种方法定量提取了震前异常变化,根据水位资料及其变化机理总结了震前水位的群体性异常特征,认为在弱震区井水位的群体性变化是分析判定地震前兆异常的有效指标。水位的群体性异常反映了震前区域应力场的调整,震源区为应力变化的集中区。

Group Characteristics of Water Levels before the Gaoyou-Baoying M4.9 Earthquake

The Gaoyou-Baoying M4.9 Earthquake is the largest earthquake in the land area of Jiangsu in recent 22 years. The water levels of partial wells in Jiangsu were uniformly declined in 2 years before this earthquake. This work mainly focuses on the variation of water levels in Jiangsu. The influences of pressure, rainfall and mining of groundwater are eliminated in the process of data processing. Two methods are adopted. One is the ratio between abnormal amplitude and annual variation amplitude, the other is the subject function. Then the forms of abnormal changes are extracted. Characteristics of group anomalyis summarized according to the mechanism and the distribution of water level change. At last, we conclude out that group anomaly of water levels is more reliable than single anomaly in weak seismic areas, and such anomaly is more likely to respond to the adjustment of stress field, where the hypo-central region can be considered as the concentration area of the stress field.