Yet another VS equation

The classical Raymer-Hunt-Gardner functional form V-p = (1 - phi)V-2(pS) + phi V-pF, where V-pS and V-pF denote the P-wave velocity in the solid and pore-fluid phases, respectively, and phi isthetotal porosity, can also be used to relate the S-wave velocity in dry rock to porosity and mineralogy as V-sDry = (1 - phi)V-2(sS), where V-sS is the S-wave velocity in the solid phase. Assuming that the shear modulus of rock does not depend on the pore fluid, V-s in wet rock is V-sWet = V-sDry root rho(bDry)/rho(bWet), where rho(bDry) and rho(bWet) denote the bulk density of the dry and wet rock, respectively. This new functional form for V, prediction reiterates Nur's critical porosity concept: The V-p/V-s ratio in dry rock equals that in the solid phase. It accurately predicts V-s in consolidated clastic and carbonate rock. Two motivations for using it are (1) it is Simple, and (2) it predicts V-s not from V-p but directly from phi and mineralogy.