<P> where K is the bulk modulus (the modulus of incompressibility), μ (\ displaystyle \ mu) is the shear modulus (modulus of rigidity, sometimes denoted as G and also called the second Lamé parameter), ρ (\ displaystyle \ rho) is the density of the material through which the wave propagates, and λ (\ displaystyle \ lambda) is the first Lamé parameter . </P> <P> Of these, density shows the least variation, so the velocity is mostly controlled by K and μ . </P> <P> The elastic moduli P - wave modulus, M (\ displaystyle M), is defined so that M = K + 4 μ / 3 (\ displaystyle M = K + 4 \ mu / 3) and thereby </P> <Dl> <Dd> v p = M / ρ (\ displaystyle v_ (p) = (\ sqrt (M / \ rho)) \) </Dd> </Dl>

What type of motion do p waves cause in the earth