Generalised surface waves at the boundary of piezo-poroelastic medium with arbitrary anisotropy.

This study considers the propagation of surface waves along all directions on the plane boundary of piezo-poroelastic half-space with arbitrary anisotropy. This generalised propagation is characterized through an anisotropic phase velocity, which should ensure the decay of wave-field with depth into the medium. A linear homogeneous system of six equations with complex coefficients governs the existence and propagation of surface waves in the considered medium. The real phase velocity of surface waves lies implicit in a complex determinantal equation, which ensures a non-trivial solution to the system of equations. Through a specific transformation, the system of complex equations is modified to yield a real secular equation, with phase velocity being the only unknown. This equation can always be solved numerically for phase velocity of surface wave along any direction on the plane boundary of anisotropic piezo-poroelastic medium. The phase velocity has been used further to calculate the components of energy flux at the boundary. Horizontal components of energy flux define the group velocity and ray direction for the surface wave. A numerical example is solved to analyse the phase/group velocity curves at the boundary of the medium.