Symmetries in the reflection and transmission of elastic waves

ry relations be ween the reflection and transmission coefficients for plane elastic waves incident upon an arbitrary horizontally stratified medium are derived by a novel approach. Previous results, particu-larly for a single interface, are obtained as special cases of this treatment. In addition, for perfectly elastic media, projection operators for travelling and evanescent waves are introduced and used to derive a number of new relationships between the reflection and transmission coefficients.