f Reciprocal Volume and Surface Integrals for Anisotropic Elastic Media

The Born (volume) and the Kirchhoff-Helmholtz (surface) integrals have traditionally been treated as completely separate formulations in the studies of reflection and transmission of waves due to smooth interfaces. A simple use of the divergence theorem applied to the Born volume integral gives a reciprocal surface scat-tering integral, which can be seen as a natural link between the two formulations. This unifying integral has been recently derived in the context of inversion. Its main properties are investigated by a stationary-phase evaluation, and the result is interpreted in ray theoretical terms.