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本文根据唐山震区的地质构造模拟制作光弹模型,以N60°E方向加压进行唐山震前应力场的光弹性模拟实验。用打孔的方法模拟强震的应力释放。实验结果表明:1.在N60°E方向压缩时,唐山—丰南一带、滦县、野鸡坨和卢龙等地区是最大剪应力集中区,与唐山7.8级、滦县7.1级地震及强余震的震中分布基本吻合。说明唐山大震及余震的发生是近东西向压应力场作用的结果。2.当唐山7.8级地震应力释放后,震前具有高应力背景值的其它地区,应力进一步加强。说明唐山地震的发生导致了应力场的重新调整,增强了强余震发震的动力条件。3.实验结果证明,在断裂带两侧、端部或几条断裂的复合部位,其主应力方向与区域应力场的总体方向比较,大致有10°～25°的偏转。强震的应力释放导致震中区附近的主应力方向与震前相比也发生约10°～20°的偏差。
In this paper, a photoelastic model is generated based on the geological structure of the Tangshan earthquake area and the photoelastic simulation of the prestabismic stress field in the direction of N60 ° E is performed. Using drilling method to simulate the stress release of strong earthquakes. The experimental results show that: (1) In the direction of N60 ° E, the areas of Tangshan-Fengnan, Luanxian, Yejiutuo and Lulong are the areas with the largest shear stress concentration, which are close to those of Tangshan 7.8, Luanxian 7.1 earthquakes and strong aftershocks The epicenter distribution of the basic agreement. It shows that the occurrence of aftershocks and large earthquakes in Tangshan is the result of the effect of near-EW stress field. 2. After the stress of the M = 7.8 Tangshan earthquake was released, the stress was further strengthened in other areas with high background stress before the earthquake. It shows that the occurrence of Tangshan earthquake led to the readjustment of stress field and enhanced the dynamic conditions of strong aftershocks. The experimental results show that the main stress direction at the two sides of the fault zone, the end part or several fractured composite parts is approximately 10 ° ~ 25 ° deflection compared with the general direction of the regional stress field. The stress release of strong earthquakes causes the principal stress near the epicenter area to deviate from the pre-earthquake by about 10 ° ~ 20 °.