Propagation of Low Frequency Surface Waves in Poroelastic Media

The problem of surface wave propagation along a flat poroelastic interface was studied in this paper. We analyzed the dispersion equations for three types of boundaries: interface between a fluid and a porous half-space, boundary of two fluid-saturated porous media (Stoneley waves) and free space (Rayleigh wave). We have shown that the dispersion equations in the low-frequency range are reduced to the dispersion equations for the equivalent viscoelastic medium, where the equivalence is understood as the equality of velocities of the compressional wave of the first kind in a porous medium and the compressional wave in one-phase medium, and equality of the shear waves velocities in these media. Using perturbation theory we have come to the conclusion that the first order perturbation correction gives the absorption coefficient proportional to the three-halves power of the frequency (f(3/2)) due to the generation of the compressional wave of the second kind at interfaces of all types. Our calculation results demonstrate that the absorption of low frequency surface waves is determined by the energy dissipation in the solid matrix for consolidated rocks. As frequency increases, hydrodynamic effects associated with a fluid relative motion in the pores begin to play a significant role.