Scattering matrix for the reflection-transmission problem in a viscoelastic medium

The reflection-transmission problem of time-harmonic waves in a viscoelastic, anisotropic and stratified solid is examined The medium is supposed to occupy the whole space. The waves are sent either from upwards or downwards with oblique incidence. The scattering matrix is defined by generalizing the procedure followed in the scalar case, namely, when the solid is isotropic and the wave incidence is normal. Existence, uniqueness and properties of the scattering matrix are discussed.