An empirical equation relating the velocities of P- (VP) and S- (VS) waves in water-saturated clastic rocks:
Preferably the equation constants should be varied empirically to fit local conditions.
- Castagna, J. P. and Backus, M. M., Eds., 1993, Offset-dependent reflectivity– Theory and practice of AVO analysis: Soc. Expl. Geophys.