Generalized-screen approximation and algorithm for the scattering of elastic waves

We describe the propagation and scattering of elastic waves in heterogeneous media. Decomposing the elastic wavefield into up- and down-going constituents allows the introduction of the 'one-way' wave equations and propagators. Such propagators account for transverse scattering and mode coupling. The generalized-screen expansion of the symbol of the one-way wave equation in medium contrast and medium smoothness induces an approximation of the propagator with an associated computational complexity of the one of the phase screen approximation. The generalized-screen expansion extends the phase-screen approach. It allows for larger medium fluctuations and wider-angle propagation. We illustrate the accuracy of the generalized screen with numerical examples.