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(一)引言从1976年7月28日在唐山发生7.8级强震起,到同年12月底止,该震区已发生5.5级(M_s)以上强余震39次。它们集中分布在唐山断裂附近及其两端偏在压缩区的一侧。与其它大震的余震分布迥然不同,具有独特的形式。它究竟由何种因素支配?是一个值得探讨的问题。正确地回答这个问题,不但有助于弄清11月15日在宁河发生的6.9级强震的性质,而且对于预测今后在唐山地区的余震活动也有帮助。由于单纯运用弹性力学理论解决的问题比较简单,所以作者引用一些破裂和光弹试验的成果进行综合分析研究。
(1) Introduction From July 28, 1976, a magnitude 7.8 earthquake occurred in Tangshan. Until the end of December of the same year, a strong aftershock of magnitude 5.5 (M_s) or above occurred in this area. They are concentrated in the vicinity of the Tangshan fault and on the opposite side of the compression zone. The aftershock distribution is quite different from other major earthquakes and has a unique form. It depends on what kind of factors? It is a question worth exploring. Correctly answering this question will not only help us to understand the nature of the 6.9 magnitude earthquake that occurred on November 15 in Ninghe, but also help predict future aftershocks in Tangshan. Since the problem solved by simply using elastic mechanics theory is relatively simple, the author makes a comprehensive analysis of the results of some rupture and photoelastic tests.