江苏及邻区震群活动特征分析

The characteristics of earthquake swarms in Jiangsu Province and its adjacent area

摘要:

系统地整理研究了江苏及其邻近地区36 次小震群活动，总结了震群活动的参数特征，探讨了震群活动与大震的关系，分析检验了前兆震群类型的判定指标。江苏地区震群活动分布集中，强度以ML 2. 0 ～ 3. 9 地震为主，震群序列总频次在30 次以下居多，持续时间在15 天以内的震群占总数的55% ;震群序列中地震总频次和震群持续时间与震群的最大震级之间不成正比;研究区78% 震群发生后对应M 4. 6 以上中强地震，其中500km 范围内时间间隔在1 年内的占对应地震总数的57% ，具有一定的中短期地震预测指示意义;震群与未来中强地震的距离较为离散，但尚无在原地发生大地震的震例。震群强度大小与未来中强地震的对应率高低和对应的地震强度大小没有明显的相关关系，震群频次的多少与其后发生地震的对应率高低也没有明显的相关关系。采用U-ρ 组合或者全组合判定震群类型的效果相对较好，检验正确率约占总数的50% ，但总体而言效果并不十分有效，需要参考其它方法和手段综合判定。

Abstract:

We systematically analyzed 36 earthquake swarms in Jiangsu Province and its adjacent area，summarized the characteristics of earthquake swarms and discussed the relationship between earthquake swarms and strong earthquakes afterwards． We also analyzed the criteria of precursory earthquake swarm． Earthquake swarms in Jiangsu Province concentrated in several places． Most of them were of magnitude ML2. 0 ～ 3. 9． For most earthquake swarms，the number of earthquakes was less than 30． Time duration for about 55% of earthquake swarms was less than 15 days． The biggest magnitude of one earthquake swarm was not proportional to the number of earthquakes and time duration． 75% earthquake swarms were corresponded with one of the forthcoming earthquakes with M ＞ 4. 6，with time interval less than one year． This shows a medium-and shortterm criteria． Distance between earthquake swarm and future earthquake distributed dispersedly． There were no earthquake occurrence in the place of earthquake swarms． There was no good relationship between the magnitude and corresponding rate of future earthquakes and magnitude of earthquake swarms． There was also no good relationship between the amount of earthquakes in earthquake swarm and the corresponding rate． It is better to use U-ρ or all-combinations to determine the type of earthquake swarm．