1. An automated method for estimating reflector dips in an image window of post-stack image traces of seismic data, comprising: flattening the post-stack image traces against a reference trace in the post-stack image traces using reflector dips to adjust depths of image points for the post-stack image traces, wherein the reflector dips are obtained from horizontal and vertical gradients of the image points in the image window of the post-stack image made up of the post-stack image traces through computer-implemented iterative inversion that inverts for the reflector dips of every grid point in the image window; constructing a model of seismic wave velocity in a subsurface region from the reflector dips; migrating the seismic data with the model of seismic wave velocity; and producing an image from the migrated seismic data showing structural features of the subsurface region and prospecting for hydrocarbons according to the structural features of the subsurface region.