An efficient 3-D curvilinear structured grid generation method for large-scale seismic wave simulation in regions with irregular topography

SUMMARY The finite difference method (FDM) based on curvilinear structured grids is an efficient numerical algorithm that retains the advantages of conventional FDM, such as computational efficiency and ease of implementation, while effectively simulating seismic wave propagation in regions with irregular topography. Grid quality plays a crucial role in the finite difference simulations, as it directly affects the reliability, stability and efficiency of the simulation. Moreover, large-scale 3-D simulations often require billion-point grids, making the efficient generation of high-quality grids a significant challenge. The curvilinear grid used in seismic wave simulations has a special feature compared to other computational problems: only the shape of the free surface is fixed, while the other boundaries remain flexible. Based on this feature, we developed a straightforward parabolic grid generation method that starts from the free surface and expands the grid layer-by-layer along the depth direction towards the pre-defined bottom boundary. Additionally, this method is highly efficient, easy to parallelize and capable of rapidly generating large-scale grids. We tested the grid generation method and its application in seismic wave simulations using five irregular topography models. Grid quality assessments demonstrate that the proposed method efficiently generates high-quality grids. Furthermore, seismic wave simulations reveal that, compared to vertically stretched grids, the generated grids reduce computation time while maintaining sufficient simulation accuracy.