P-wave modulus

The P-wave modulus is an elastic modulus, not often used in rock physics interpretation. It is usually denoted M.

M is analogous to the shear modulus, &mu; and is most easily understood in acoustic terms:


 * $$ M = \rho V_\mathrm{P}^2$$

Therefore M&rho; is equal to IP2, so one could invert for it relatively easily, as one does for &lambda;&rho;. One could consider M as a cousin to bulk modulus, K, in the same way that the 1st Lamé parameter is a cousin to shear modulus, &mu;.