2022年3月16日日本近海7.4级地震地震动场三维有限差分模拟

3D finite-difference numerical simulation of ground motion in Japan Namie M7.4 earthquake, March 16, 2022

2022年3月16日,日本本州东岸近海发生7.4级地震,强烈的地面运动造成了严重的工程结构破坏及经济损失。为深入了解此次地震的地震动特征,采用精细化的三维速度结构模型及震源运动学破裂初步反演结果,利用交错网格有限差分法模拟了此次地震中地震波的传播过程,给出了地震动场的数值模拟结果,并与研究区域内K-NET台站记录的观测记录进行对比。模拟速度波场快照表明研究区域内地震波的传播过程十分复杂,海底界面复杂的散射波显示地震波在海底高速介质与表层介质间的多次反射;关东、新潟等地区的区域放大效应体现了深厚沉积层是影响地震动的重要因素;平行于断层迹线的部分台站的观测与模拟速度时程波形具有较为一致的波形与幅值。模拟与观测记录的地面峰值速度空间分布特征较为相似,近断层台站模拟记录的水平向峰值地面速度约2~8 cm/s,普遍小于观测记录峰值(约6~20 cm/s),可能与采用的三维速度结构模型中低速海水层的吸收作用有关。

On March 16,2022,an earthquake of magnitude M7.4 occurred off the northeast coast of Honshu,Japan,and the strong ground motion caused severe engineering structural damage,human casualties,and great damage to property.To investigate the ground shaking characteristics of this earthquake,we used a detailed three-dimensional velocity model,and then simulated the propagation process of seismic waves by using the finite-difference method with staggered-grid based on the preliminary inversion results of the kinematics slip distribution of the source.At the end,numerical simulation results of the ground shaking field are given and compared with the observations recorded at the K-NET station in the study area.Snapshots of the simulated velocity wavefield show that the seismic wave propagation process in the study area is very complicated.Complex scattered waves at the seafloor interface reveal the multiple reflections of seismic waves between the high-speed submarine medium and the surface medium.The regional amplification effect in the Kanto and Niigata areas reflects the importance of deep sedimentary layers as a factor influencing the distribution characteristics of strong ground motion.The seismic waveforms and amplitude of simulated velocity from stations located in a trace with fault parallel are consistent with the observed results.The simulation results provide satisfactory agreement in terms of the spatial distribution of peak ground velocities.The simulated peak ground velocities in horizontal component recorded at the near-fault stations are approximately equal to 2~8 cm/s,which is generally smaller than the recordings(about 6~20 cm/s),and this might be attributed to the absorption effect of the low-velocity seawater layer used in the 3D velocity structure model.