As every geophysicist knows, the reflection amplitude versus angle for reflection from an interface between two elastic rocks is given by the Zoeppritz equation. The Zoeppritz equation in the forward mode predicts the amplitude of the reflection, given the angle, the compressional and shear velocities, and densities of the rocks that form an interface. It is possible to turn the Zoeppritz equation around and ask, given the reflection amplitude and angle, compressional velocities and densities, what is the shear velocity of the lower rock? This turning around of the equation is called the inverse mode of the Zoeppritz equation.
Research Article|October 01, 2004
Rock properties and amplitude versus angle
The Leading Edge (2004) 23 (10): 986-988.