Evaluation of pulse-like ground motion for the northern Xiaojiang fault under different rupture scenarios

Pulse-like ground motion in the near-fault region may cause serious damage to large engineering structures. To reveal the formation mechanism and engineering characteristics of velocity pulse from the seismic source， this study uses the finite-difference method to simulate the ground motion excited by the northern Xiaojiang fault with high seismic risk under different rupture scenarios. Based on the simulation results of the source models and crustal structure model， the effects of fault rupture velocity on ground motion time history， peak distribution， seismic response spectrum and wavefield are evaluated. The results show that the related parameters of asperity contribute to the waveform characteristics and spatial distribution of near-fault velocity pulses. When the rupture velocity of the seismic fault is close to the propagation velocity of the shear wave in the regional crust， the forward directional pulse is more easily recorded by the receiving station in front of the rupture. For the three-component ground motions， the velocity is the largest and the distribution range is the widest in the fault-normal direction， and the ground motion intensity generated by supershear rupture is generally greater than that generated by subshear rupture. The seismic waves excited by different rupture tips in the supershear earthquakes form obvious Mach cones under constructive interference， and the strong pulse-like ground motion of the northern Xiaojiang fault may cause greater seismic damage to the Qiaojia area. The pulse-like ground motion in the near-fault region ahead of the rupture should be the focus of seismic hazard analysis and earthquake prevention.