Q值异常与包头西6.4级地震

THE Q VALUE ANOMALY AND THE WEST BAOTOU MS6.4 EARTHQUAK E

１９９５年，我们采用Ｐ波初动半周期残差方法研究了内蒙古西部地区的震源介质参数，结果发现：西山咀周围地区Ｑ值高达８７３，其他地区均在５００以下。因而指出：乌拉特前旗（包头西）附近地区近期有发生中强地震的可能性。果然，在１９９６年５月３日包头西发生了６．４级地震。５月６日，我们利用丰富的余震资料又计算了该区的Ｑ值，发现震后Ｑ值已由８７３下降为３２３。这一结果不仅证实了包头西地震前高Ｑ值异常的存在，而且也为当时包头西６．４级序列类型（主—余型）的判定提供了一条依据。

Abstract The Q value in the west Inner Mongolia had been studied by the residual method of half period of P wave first motion.The result showed the Q value had increased very high in 1995,it was 873 around Xishanzui station.In other place,t he Q were under 500.This is the evident anomalism.So we clearly pointed out the region had dangerousness about Ms6.4 earthpuake in Wulateqianqi(west Baotou) rec ently.As expected,the M S6.4 earthquake occurred on May 3 1996 in t he west Baotou.We studied the Q at the same region by the post shock data again. The Q had reduced to 323.This result had proved the existim of high Q anomalism before the earthpuake and provided the proof to affirm the type(major-post shoc k)of the M S6.4 earthpuake in the west Baotou.