Asymptotic analysis of surface waves at vacuum/porous medium interface: Low-frequency range

Existence and propagation of the surface waves at a free interface of a saturated porous medium are investigated in the low-frequency range. Similar to the high-frequency range, two types of surface waves are proven to be possible: the generalized Rayleigh wave, which exists always and propagates almost without attenuation and the Stoneley wave, which exists for a limited range of wave numbers and is strongly attenuated. Bifurcation behavior of both the Stoneley wave and the Biot slow bulk wave depending on wave number is revealed