A Physical-based Spectrum-compatible Ground Motion Simulation Method for Multi-Point Excitations

Abstract

Multi-point excitations are generally required to analyze the seismic response of spatially distributed structures, such as pipelines or long-span bridges. Simulated or synthetic ground motions, as a surrogate of recorded ones, have been widely used in earthquake engineering practice. When simulating ground motions for multi-point excitations, one of the key challenges is to appropriately represent the spatial correlation characteristics of acceleration-, velocity-, and displacement-time histories at neighboring sites. To address this issue, this study proposes a physical-based ground motion simulation method based on seismic physical process. Within this method, the kinematic finite-fault model is first employed to describe the source process, and the frequency-wavenumber Green's function is then utilized to calculate the propagation of seismic waves. Then, a frequency-domain adjustment is performed to ensure congruence with the design response spectrum. Ground motions at multiple sites can then be simulated under given scenario earthquakes, in which the spatial cross-correlation characteristics of these acceleration-time histories are properly quantified during the modeling of the physical propagation process of seismic waves. Moreover, by taking the 2019 moment magnitude (M_w) 7.1 Ridgecrest earthquake as a demonstrated example, synthetic ground motions are simulated using both the proposed and conventional methods, respectively. The simulation results are then compared with the data recorded from a dense array located at the Nevada National Security Site. It is found that the characteristics of the simulated motions of the proposed method are generally consistent with the recorded ground motions. Additionally, dynamic analyses are performed for a 300-m-span continuous box girder bridge using the simulated and recorded ground motions as the multi-point excitations, respectively. It is indicated that the difference of the dynamic responses by employing the simulated motions and recorded motions is generally smaller than 12%, validating the rationality of the method developed. Therefore, the proposed method can be readily used to simulate a set of ground motions at multiple sites, and to assess the seismic performance of spatially distributed structures by multi-point excitations.