凡余震频次超过余震衰减曲线误差包线,同时满足以下条件:在不超过半个月的时间内,至少有三个震级相近的主要地震M_1>M_2>M_3,△M_(1,2)≤1、△M_(2,3)≤1(△M_(1,2)=M_1—M_2,△M_(2,3)=M_2—M_3)时,我们称其为余震震群。 作者曾研究过邢台、海城、唐山等强震的余震活动与华北地区地震活动的关系,本文拟对发生在海域内的1969年7月18日渤海7.4级地震进行类似的研究。由于没有地 Where the frequency of aftershocks exceeds the error envelopes of aftershock decay curves, at the same time the following conditions are met: at least three major earthquakes of similar magnitudes M_1> M_2> M_3, △ M_ (1,2) ≤1 in no more than half a month, △ M_ (2,3) ≤1 (△ M_ (1,2) = M_1 -M_2, △ M_ (2,3) = M_2-M_3), we call them the aftershock swarm. The authors have studied the relationship between the aftershock activity of strong earthquakes such as Xingtai, Haicheng and Tangshan and the seismic activity in North China. This paper intends to conduct a similar study on the July 7.4, 1969 Bohai 7.4 earthquake that occurred in the sea area. Because there is no ground