Generalized impedance boundary condition modeling a thin elastic layer between two elastic half-spaces

The generalized impedance boundary condition modeling a thin elastic layer separating two elastic half-spaces permits one, in the problem of transmission of an elastic wave through the layer, to eliminate from the consideration the wave field in the layer and therefore to considerably simplify the problem. In particular the deduced general impedance boundary condition permits one to obtain the reflection and refraction coefficients of a plane elastic wave incident on a thin elastic layer separating two elastic half-spaces