时间域广义2.5D一阶波动方程曲网格有限差分法数值模拟

The 2.5D seismic wavefield numerical stimulation employs the point source in 2D geological models to calculate 3D seismic wavefields. In this paper, we present a generalized 2.5D first-order time-domain wave equation that can be applied to different media (acoustic isotropic, elastic isotropic, and elastic anisotropic) and various boundary conditions (acoustic free-surface, solid free-surface, and solid-liquid boundary). The wave equation is solved by a curvilinear-grid finite-difference method. A comparison of 2.5D numerical solutions, 3D analytic solutions, and 3D numerical solutions in different homogeneous medium models (acoustic isotropic, elastic isotropic, and elastic anisotropic) verifies the correctness of the derived equation and the numerical solution method. It also demonstrates that compared with the 3D numerical method, the 2.5D numerical method has great advantages in calculation efficiency and memory footprint. The 2D numerical solutions cannot be applied directly in that they suffer significant amplitude distortion and phase shifts due to an artificial line source applied in this method. The results of numerical experiments show that the proposed 2.5D numerical simulation method can be applied to geological models with different boundary conditions (acoustic free-surface, solid free-surface, and solid-liquid boundary). In addition, unlike the 2D wavefield numerical simulation method, the 2.5D method can be directly employed to process actual point source observation data such as 2.5D reverse-time migration.