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采用美国南加州地震委员会(SCEC)Steven Day博士提供的三维有限差分断层瞬态破裂动力学模型(3DFDM),以1976年唐山Ms 7.8地震为例,从简化的断层双侧破裂模式出发,对该地震发震断层的动态破裂过程及近断层地表运动特征进行了仿真模拟和计算.研究区域为围绕发震断层200 km×140 km×40 km(深度)的长方形块体组成,模拟计算的空间分辨率和时间分辨率分别为200 m和0.012 s,形成的空间网格节点数为1051×701×201.在DELL小型工作站上,我们实现了对源程序的移植和并行计算.同时,通过引进计算机可视化技术,对模拟数据进行了3D/4D解释分析.另外,在对源程序修改过程中,实现了对京津唐地区三维地壳速度结构的嵌入,在一定程度上增强了对地震波传播以及地面运动模拟的真实性,并讨论了地震破裂的方向性对近断层地表运动的影响.最后根据初步研究结果结合京津唐地区活动断层构造特征,对唐山M_S7.8级主震后随之而来的1976滦县M_S7.1级余震及宁河Ms6.9级余震的动态触发机制提出了新的解释.由于受主震破裂方向性作用的影响,使得主震对后续两个较大余震产生的动态应力变化的峰值在断层的走滑方向上较大,为2～3 MPa,在逆冲方向上较小,为0.1～0.2 MPa.即唐山主震的发生使得其周边的应力场有一个瞬态的应力调整,唐山主震对后续余震的发生有促发作用.
Based on the 3D Finite Difference Fault Transient Cracking Dynamics Model (3DFDM) provided by Dr. Steven Day of SCEC, taking the Tangshan Ms 7.8 earthquake in 1976 as an example, The dynamic rupture process of the seismogenic fault and the characteristics of the surface movement near the fault are simulated and calculated.The research area is composed of rectangular blocks around 200km × 140km × 40km (depth) of the seismogenic fault, and the spatial resolution The rate and time resolution are respectively 200 m and 0.012 s, and the number of space grid nodes formed is 1051 × 701 × 201. On the DELL small workstation, we have realized the transplantation and parallel computing of the source program.At the same time, through the introduction of computer Visualization technology, 3D / 4D interpretation and analysis of the simulation data.In addition, in the process of source program modification, the embedding of 3D crustal velocity structure in Beijing, Tianjin and Tangshan area is strengthened, to a certain extent, the seismic wave propagation and ground motion are enhanced Simulates the reality and discusses the impact of the direction of the earthquake rupture on the near-surface ground motion.Finally, according to the preliminary research results, combined with the active faults in Beijing-Tianjin-Tangshan area Characteristics of Tangshan M_S7.8 main shock after the 1976 Luanxian M_S7.1 aftershock and Ninghe Ms6.9 aftershock dynamic trigger mechanism proposed a new explanation.Because of the main shock rupture direction The peak value of the dynamic stress changes caused by the two main aftershocks of the main shock is larger in the strike-slip direction of the fault (2 ~ 3 MPa) and smaller in the thrust direction (0.1 ~ 0.2 MPa). That is, the occurrence of Tangshan mainshock makes the stress field around it have a transient stress adjustment, and the Tangshan mainshock can promote the occurrence of subsequent aftershocks.