I am modelling a seismic wave equation using FEM. In the few papers that I read, I understand the following: (Kindly correct me if you disagree)
A shear (secondary wave - no change of volume) is more important to model than the compression (primary wave - no rotation) as it brings more devastation than the latter.
The elastic wave equation is a better representative of a seismic wave than the acoustic wave equation because simulating it, we propagate both 'p' and 's' waves in the mesh instead of just 'p' which we get from simulating acoustic equation. (p - primary; s- secondary)
The elastic wave equation also known as Navier's equation of elastodynamics can be multiplied by curl operator to give the Shear wave equation, or it can be multiplied by divergence operator to give the acoustic wave equation. Both shear and acoustic wave equations are very similar except for the expressions for their speed. This expression is what differentiates both the equations and is responsible for the shape that they take. I say this because I found both expressions to be exactly same except that the acoustic wave also uses Lame's parameter $\lambda$ in addition to shear modulus $\mu$ and mass density $\rho$.
My main concern is to know which waves are propagating in my mesh if I am simulating the elastodynamic or elastic wave equation. Is it both 'p' and 's'?