Coupled space-domain elastic migration in heterogeneous media

We develop a new space-domain elastic migration method for heterogeneous media based on downward continuation. This method uses the concepts of the recently developed Arbitrarily Wide Angle Wave Equations. The coupled oneway propagation of pressure and shear waves is modeled by attaching a virtual half-space to each depth step, which is represented by special complex-length finite elements. Although formulated using finite element concepts, the method is eventually implemented using an implicit finite difference method in the frequency-space domain. The impulse response of the proposed method illustrates that P, S and head wave fronts are captured accurately for almost the entire range of the dip angles. The effectiveness of the method is illustrated by imaging a synthetic heterogeneous exploding reflector model.