A Fast Half-Space Indirect Boundary Element Method for Broadband Basin Amplification Effect Study

Studying the amplification behavior of sedimentary basin regions often requires large-scale numerical simulations and repeated runs with varying source configurations, making computational costs prohibitively high. To address this challenge, we present an efficient three-dimensional Indirect Boundary Element Method (IBEM) framework for simulating broadband and time-domain wavefields in near-fault sedimentary basin environments. The proposed framework incorporates half-space Green’s functions computed via the Dynamic Stiffness Matrix Method (DSMM) that could significantly reduce computational cost with fewer discretized elements compared to conventional IBEMs using full-space Green’s functions. The framework is rigorously validated against analytical solutions for degenerate models. To demonstrate its effectiveness, numerical examples of a homogeneous half-space model containing basin structures are provided for simulating near-fault basin responses up to 5 Hz, involving dip-slip point sources at various horizontal locations. The results successfully capture key features of basin amplification in both frequency and time domains and show good agreement with previous studies. Computation time statistics reveal that, once the Green’s function matrix is established, simulations for different source configurations at each frequency can be completed within seconds. The proposed IBEM framework offers a promising and scalable tool for earthquake engineering and seismological analysis in complex near-fault settings.