强震发生前中小地震活动特征的初步研究

THE PRELIMINARY RESEARCH OF MID-SMALL EARTHQUAKE ACTIVITIES BEFORE STRONG EARTHQUAKES

针对西北地区4次6级强震前一定范围内中小地震活动进行分析,得出在强震发生前中小地震的活动有两个不同的时段:(1)中小地震频次高、分布有序性低的A时段和中小地震频次低、分布有序性高的B时段;(2)中小地震的活动在某些方位上呈现优势分布。对上述现象产生的原因进行了粗浅的讨论。

By ananlyzing the activities of mid-small earthquakes in certain region before 4 strong earthquakes with M_S6 in northwest area, we obtain that the activities of mid-small earthquakes have two different time-segment before the strong earthquake occurred. (1) The A time-segment is that the frequency of mid-small earthquakes is high, the order of their distribution is low. While the B time-segment is that the former is low, the latter is high.(2) The activities of mid-small earthquakes appeared dominant distribution in some directions. We discussed simply the reason of appearing the above-mentioned phenomenon.