Are these values typical ? 400 km / s )
The velocity of P - waves in a homogeneous isotropic medium is given by formula_1 where " K " is the bulk modulus ( the modulus of incompressibility ) , " formula_2 " is the shear modulus ( modulus of rigidity , sometimes denoted as " G " and also called the second Lamé parameter ) , " formula_3 " is the density of the material through which the wave propagates , and " formula_4 " is the first Lamé parameter .