A method and computer-readable medium for determining a scattered wave particle velocity for a formation is disclosed. In aspects, the method may include: defining an embedded grid of the formation, and defining a contrast grid of the formation that includes a contrast feature of the formation; calculating a Green's function over the embedded grid; calculating a first scattering vector of the contrast feature for a first offset between the embedded grid and the contrast grid; determining the scattered wave particle velocity for the contrast feature at the first offset using the calculated Green's function and the first scattering vector; calculating a second scattering vector of the contrast feature for a second offset between the embedded grid and the contrast grid; and determining the scattered wave particle velocity for the contrast feature at the second offset is determined using the calculated Green's function and the second scattering vector.