包头西M_S6.4地震形变前兆异常及特征分析

Characteristics of the fault deformation precursory anomaly before the west Baotou earthquake M_S=6.4

1996年5月3日在包头市西部(109.6°E,40.8°N)发生Ms6.4地震。呼和浩特市及陕西和山西北部强烈有感。这次地震发生在人口为百万以上的城市,给包头市及邻区造成很大的损失,因此认真分析研究这次地震的前兆异常及其特征,对全面认识包头西Ms6.4地震的成因机理有其重要意义。一、包头西Ms6.4地震的主要形变前兆异常内蒙古地区跨断层流动水准测量共有三处测点,均分布在包头市的东部地区(图1)。这三处测点在包头西Ms6.4级地震前均有异常变化。

Before the occurrence of the west of Baotou earthquake(Ms=6.4)in Inner-Mongolia on May 3,1996,all the observatory sites within 240 km in distance had observed significant medium—term anomalies.The data analyses show that the crustal deformation across the E-W trending Daqingshan piedmont fault and some other NE-trending faults behaved as tensile activities.This may suggests that ithe event resulted from compression in a direction between NE and EW.