Removing the stability limit of the time-space domain explicit finite-difference schemes for acoustic modeling with stability condition-based spatial operators

摘要

The time step and grid spacing in explicit finite-difference (FD) modeling are constrained by the Courant-FriedrichsLewy (CFL) condition. Recently, it has been found that the spatial FD coefficients may be designed through simultaneously minimizing the spatial dispersion error and maximizing the CFL number. This allows one to stably use a larger time step or a smaller grid spacing than usually possible. However, when using such a method, only second-order temporal accuracy is achieved. To address this issue, I propose a new method to determine the spatial FD coefficients, which simultaneously satisfy the stability condition of the whole wavenumber range and the time-space domain dispersion relation of a given wavenumber range. Therefore, stable modeling can be performed with high-order spatial and temporal accuracy. The coefficients can adapt to the variation of velocity in heterogeneous models. In addition, based on the hybrid absorbing boundary condition, I develop a strategy to stably and effectively suppress artificial reflections from the model boundaries for large CFL numbers. Stability analysis, accuracy analysis, and numerical modeling demonstrate the accuracy and effectiveness of my proposed method.