Multi‐mode inversion of dispersive surface‐wave free fields in layered media

Abstract

Inversion of surface‐wave free fields is of great importance in providing seismic excitations for the finite element (FE) analysis of soil–structure interaction (SSI) systems. In the case of layered media, the propagating surface waves are characterized by their unique dispersion property, resulting in dispersive multi‐mode surface wavefields. Available studies primarily focus on only the fundamental mode and neglect the influence of higher modes, which fail to identify the real structural response characteristics. To enhance the precision of seismic excitations for SSI systems situated in layered media, a multi‐mode inversion method for dispersive surface‐wave free fields is proposed in this study. The proposed method employs the energy flow density to characterize the participation volume of dispersive modes, and further calculates corresponding modal participation factors by combining with the dispersion curve and dynamic‐stiffness matrix (DSM) method. The modal participation factors are then utilized to assign the ground surface components of each mode and invert respective single‐mode surface‐wave free fields. Based on the mode superposition theory, all the single‐mode surface‐wave free fields are finally superimposed to construct the multi‐mode wavefields. The accuracy of the proposed method is thoroughly verified and validated across various types of layered media. Furthermore, the engineering application of the proposed method is illustrated by performing the FE analysis on an SSI example. The analysis results highlight the significant participation of surface waves' higher modes in structural seismic responses, particularly in the weak‐interbed type media.