3D-FDM for elastic wave modeling in the presence of irregular topography by using unstructured index array representation on a GPU

Ivan Sanchez, William M. Agudelo, Daniel O. Trad, Daniel Sierra

Simulating seismic wave propagation in complex structures geological areas is a challenging task in exploration geophysics. Realistic simulations of seismic waves in foothill areas face challenges from complex near-surface models that include rough topography, irregular bedrock interfaces, low-velocity surface sediment, and significant heterogeneities.Although existing numerical methods can solve the seismic wave equation under these conditions, they typically require a discretization model with a small grid size, leading to a high computational cost. To address this, we introduce a novel 3D solver (PMFD3DGPU),based on the finite-difference method for elastic wave propagation in the presence of irregular topography and designed for GPU acceleration. Our solver features an innovative approach that involves an unstructured index array representation (UIAR) to implement the parameter modified (PM) formulation that satisfy the free-surface condition for topographic variations. We validated the PMFD3D-GPU solver against the well-knownSPECFEM3D solver, and in conditions of rough topography, we demonstrated misfit errorsof less than 1% in most cases. Additionally, our solver accelerates the simulations,achieving a speed-up approximately 20 times faster compared to the CPU implementation.Therefore, PMFD3D-GPU solver enables cost-effective realistic and detailed simulationsof near-surface seismic scattering using heterogeneous earth models with irregular topography.