Since 1970, 13 earthquakes of M≥5. 0 occurred in the Northeast China, of which 8 medium-strong earthquakes are independent in space and time. Having studied small earthquakes before the 8 medium-strong earthquakes systemically, we found that these small earthquakes activities increased. Combining with characteristics of the small earthquake activities in the Northeast China, we proposed and applied the new method whether the spatial changing pattern of small earthquake activities change the small earthquake frequency. The result showed that the small earthquake frequency calculated by using new method could pick up anomaly frequency of small earthquakes before medium-strong earthquake. We could get medium-short-term abnormal indexes effectively before the medium-strong earthquakes in Northeast China.%1970年以来东北地区共发生13次5.0级以上地震,其中8次地震在时间和空间上相对独立.通过系统研究东北及其邻区这8次中强地震前的小震,发现这些中强地震前存在比较明显的小震增强现象.结合东北地区小震活动的特点,提出根据小震活动空间格局是否改变统计小震频度的方法,并进行了初步的应用.结果表明:利用新方法统计小震的频度更能突出中强地震前的小震频度异常,能够有效的提取东北地区中强地震前的中短期异常指标.
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