利用近代微震资料研究地震危险性

Studies of Earthquake Risk Using Microseismicity Data in Modern Times

利用１９７０～１９９３年华北地区ＭＬ≥２０的微震资料，根据其地震活动特点，从中挑选了一些有代表性的区域，做其ＧＲ关系曲线。由该曲线可得到每个震级的年频次。同时，由该区域的历史地震（１３００～１９９３年）可得到较大震级的实际年频次。两者对比，发现具有很好的一致性。因此，当选取合适的区域时，利用近代微震资料完全可以推测出该区域较大地震的活动情况。但同时有两点需注意：（１）利用微震资料进行统计时，得到的是一个地震活动体系（或断层体系）中各种震级的地震年频次，是对一个体系整体活动情况的估计；（２）在所用微震资料时间段内及其附近发生大地震时，在包括该地震的地震活动体系中。

This paper selects some representative regions to get their G R relation curves according to their seismicity characteristics,by using M L ≥2 0 microseismicity data(1970～1993) in North China.The annual occurrence rate of each magnitude can be inferred from the G R relation.At the same time,the real annual occurrence rate on larger magnitude can be calculated by the historic earthquakes(1300～1993)recording in the same region.It seems that both data are almost the same.Therefore,the rate of the larger magnitude can be obtained by using microseismicity data when the proper region is selected.But two points can be noticed:(1)It can only get annual occurrence rate in a seismicity system,and estimate whole situation of the system.(2)When there is a very large earthquake in and near the period in which microseismicity data are applied,the real occurrence rate of the system including this large earthquake can not be obtained by this method.