Irregular surface seismic forward modeling by a body-fitted rotated–staggered-grid finite difference method
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Finite-difference (FD) methods are widely used in seismic forward modeling owing to their computational efficiency but are not readily applicable to irregular topographies. Thus, several FD methods based on the transformation to curvilinear coordinates using body-fitted grids have been proposed, e.g., stand staggered grid (SSG) with interpolation, nonstaggered grid, rotated staggered grid (RSG), and fully staggered. The FD based on the RSG is somewhat superior to others because it satisfies the spatial distribution of the wave equation without additional memory and computational requirements; furthermore, it is simpler to implement. We use the RSG FD method to transform the first-order stress–velocity equation in the curvilinear coordinates system and introduce the high-precision adaptive, unilateral mimetic finite-difference (UMFD) method to process the free-boundary conditions of an irregular surface. The numerical results suggest that the precision of the solution is higher than that of the vacuum formalism. When the minimum wavelength is low, UMFD avoids the surface wave dispersion. We compare FD methods based on RSG, SEM, and nonstaggered grid and infer that all simulation results are consistent but the computational efficiency of the RSG FD method is higher than the rest.
KeywordsFinite difference forward modeling grid staggered rotated body-fitted surface free boundary
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We thank Komatitsch et al. for providing the open source code of the 2D spectral element method (SPECFEM2D) (https://doi.org/geodynamics.org/cig/software/specfem2D).
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