Variable grid for finite difference computation

A computer system and a computer-implemented method for evaluating a geophysical model using a grid of points representing locations in a subsurface geological region are disclosed. The method includes storing a geophysical model of the subsurface geological region in a computer readable memory and defining, for the geophysical model, the grid of points representing the locations in the subsurface geological region. The grid of points comprise a plurality of points extending in at least one direction. The plurality of points are variably spaced apart in the at least one direction. The method further includes evaluating, by the computer, the geophysical model using the grid of points.