组合模式与地震图上的终止震相——兼论唐山地震的震源破裂过程

本文从成因上研究了组合模式与地震图上终止震相的联系。组合模式因积累单元端部有剪应力集中区,张应力让位区和弱介质让位区,故断层传播到积累单元端部要加速,然后急剧停止,这就导致了终止相的形成。这些端部因素是调整单元的存在引起的。地震图上的终止震相的发育程度与组合模式中的调整单元让位的充分程度有关,让位条件愈好,终止震相愈明显。最后本文以唐山地震为例进行了实际讨论。

COMBINATION MODEL OF EARTHQUAKE DEVELOPMENT AND STOPPING PHASE IN SEISMOGRAMS-On the Rupture Process of the Tangshan Earthquake

Firstly, this paper discussed the causal relationship between the combination model and stopping phase in seismograms. According to the combination model which was proposed by Guo Zhenjian et al in 1973, there are shear-stress concentration region, tension-stress abdicatation region and weaker medium abdication region at ends of accumulation element. When a rupture propagate from a stronger medium region into a weaker medium abdicatation region, the rupture will be speeded, then stopped quickly, thus stopping phase is produced. These termination factors are caused by the adjustment element of the combination model. The amplitude of stopping phase is related to abdication degree of the adjustment element. The better abdication degree, the more striking stopping phase.Secondly, this paper took the Tangshan earthquake of July 28, 1976 for example to study the stopping phase and rupture process. The result shows that the Tangshan earthquake is a bilateral rupture, total length is 96 km.