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1975年海城7.3级大震前后,辽宁地区地震活动的时空分布具有显著不同的特征。大震前,小震活动主要集中在辽东半岛,以海城为中心逐渐形成围空区,小震活动自外围向震中区迁移和集中,震前一年,能量及频次急剧增加。大震以后地震活动明显的受北东和北西两个构造方向的控制,形成NE和NW方向的地震活动带。全区出现明显的地震活动重复周期,时间为19个月左右,近于”倍九“的关系。辽西地区的地震活动受唐山地震余震活动的控制,两者呈紧密的呼应关系,形成广义的余震。
Before and after the Haicheng MS 7.3 large-scale earthquake in 1975, the spatial and temporal distribution of seismic activity in Liaoning Province had significantly different characteristics. Before the earthquake, the activities of small earthquakes mainly concentrated in the Liaodong Peninsula, and gradually formed the enclave centered around Haicheng. The activity of small earthquakes migrated and concentrated from the periphery to the epicenter. Before the earthquake, the energy and frequency increased sharply. After the earthquake, the seismic activity was obviously controlled by two tectonic directions of NE and NW, forming the NE and NW seismic activity belt. Significant seismic activity in the region repeated cycles, time is about 19 months, nearly “times nine” relationship. The seismic activity in western Liaoning is controlled by the aftershock activity of the Tangshan earthquake, and the two are closely echoed to form a generalized aftershock.