An optimal 125-point scheme for 3D frequency-domain scalar wave equation

To improve accuracy and efficiency of forward modeling in the frequency domain, a 125-point finite-difference scheme is proposed. At present, the optimized difference format based on the rotating coordinate system is widely used, but it only suitable for equally sampling interval, and the optimized difference format based on the average-derivative method can be applied to different spaced sampling while improving the sampling accuracy. In this paper, we firstly introduce a 125-point optimized scheme for the three-dimensional scalar wave equation. Then, according to the optimized difference scheme, the 125-point optimized difference coefficient is calculated for different spatial sampling spacing ratios. Compared with the optimal 27-point scheme, grid points number reduces from 4 points to 2.5 per wavelength, higher efficiency and suitable for unequal directional sampling intervals. In addition, the higher accuracy of 125-point scheme means it requires more storage and computation cost. Numerical results show that the optimized 125-point difference format has higher accuracy than the classical 27-point difference format.