SURFACE ACOUSTIC WAVES AT A BOUNDARY OF TWO POROUS MEDIA SATURATED WITH METHANE HYDRATE AND WATER (ICE)

This paper describes the propagation of vertically polarized surface acoustic waves at a boundary between porous media saturated with methane hydrate and ice (water), as well as horizontally polarized waves at an interface between a hydrate-saturated porous medium and a water-saturated porous medium. A mathematical model is developed for flat harmonic waves. The porous medium saturated with gas hydrate or ice (water) is assumed to be an elastic isotropic body. The mathematical model includes wave equations for scalar and vector potentials of wave velocities with account for displacement and stress vector components of the medium particles. Conditions for the continuity of displacements and stresses in porous media at the interface are given. The obtained dispersion equations are analyzed, and the results are compared with experimental data. It is revealed that the penetration depth of a transverse wave into hydrate-saturated sand is greater than the penetration depth of a longitudinal wave. It is proposed to determine the presence of hydrate-saturated sand at positive temperatures of bottom sediments by the penetration depth and the variation of the zero mode velocity of the horizontally polarized wave.