1975年海城M_S7.3地震强地面运动模拟

Simulation of strong ground motion by the 1975 Haicheng M_S7.3 earthquake

地震强地面运动预测对工程的抗震设计,地震危害性分析以及减轻特定地区可能发生的大地震所造成的灾害具有重要的作用.本文根据辽宁省海城地区的地质资料和发生于1975年2月4日辽宁省海城市的M_s7.3地震资料,分别构造了海城地区的地下速度结构和海城地震的震源模型,并且使用可以准确描述地形起伏的曲线网格有限差分方法计算了海城地震的波场传播过程.通过对计算得到的波场快照、合成理论地震图以及地震烈度的分析表明:(1)震源模型、地下的速度结构和地形起伏对海城地震的波场传播模拟具有重要的影响,它们所产生的近断层效应、方向性效应和盆地效应明显;(2)通过计算得到的海城地震的理论烈度分布与通过震后调查得到的烈度分布大体符合,验证了本文所构造的震源模型和速度结构的合理性.

Strong ground motion prediction is of much significance for seismic design of buildings, seismic hazard assessment and mitigating the devastation caused by a possible large earthquake that may occur in a particular area. In this study, the velocity model of the Haicheng area and an earthquake source model are established based on geological and seismic data of the Ms7.3 earthquake in Haicheng city, Liaoning province, on 4 February 1975. The 3D curvilinear grid finite difference method that can handle free surface topography with high accuracy is adopted to simulate seismic-wave propagation. The computed snapshots, synthetic waveforms and the distribution of seismic intensity show that （1） the seismic source model, velocity structure as well as free surface topography have major effects on the simulation of seismic wavefield propagation of the Haicheng earthquake. The near-fault concentration effect of peak ground velocity, rupture directivity effect, and basin effect are obvious. （2） The computed seismic intensity map is well consistent with observed intensity map, which validates the built earthquake source model and the velocity model in this study.