In linear elasticity, the P-wave modulus
, also known as the longitudinal modulus, or the constrained modulus, is one of the elastic moduli available to describe isotropic homogeneous materials.
This occurs when expansion in the transverse direction is prevented by the inertia of neighboring material, such as in an earthquake, or underwater seismic blast.
This is equivalent to stating that where VP is the velocity of a P-wave and ρ is the density of the material through which the wave is propagating.
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