本文从震源区、发震构造和破裂方式等的相似性,认为1978年5月18日海城6.0级地震是1975年7.3级地震的晚期强余震活动。结合震区地质构造的分析,提出晚期强余震的发生是与残余闭锁区的崩解相联系。因而,主震后,震源区残余的闭锁结构处正是尔后晚期强余震的所在位置。文中还对这种残余闭锁区的形式及其与粘滑机制的关系作了分析。 In this paper, from the similarity of source area, seismogenic structure and mode of rupture, it is considered that the May 18th, 1978 Haicheng M6.0 earthquake is the late strong aftershock activity of the M7.3 1975 earthquake. Based on the analysis of the geological structure of the earthquake zone, it is proposed that the occurrence of the late strong aftershock should be related to the disintegration of the residual locked zone. Therefore, after the main shock, the residual block structure in the source area is the location of the later strong aftershock. The article also analyzes the form of this residual lockout area and its relationship with stick-slip mechanism.