Rayleigh And Stoneley Waves On Cylindrical Boundaries

The propagation of Rayleigh and Stoneley waves on boundaries with topography has been treated using an approximate method. Where subsurface layering is not important, the properties of boundary waves are controlled by the shape of the boundary. Arbitrary linear topographic features have been approximated by a series or cylindrical surface elements.;In order to apply this approximation, the description of Rayleigh waves on cylindrical surfaces has been extended to lower frequencies. The period equation for Stoneley waves on cylindrical boundaries was solved numerically for a large range of frequencies. It was found that lower frequency Rayleigh waves on concave cylindrical surfaces have significant attenuation in the azimuthal direction. Stoneley waves on cylindrical boundaries are also attenuated. Both Rayleigh and Stoneley waves are dispersive on either type of cylindrical surface.;Several arbitrary topographic features were represented by a series of cylindrical surface elements and the properties of boundary waves on cylindrical surfaces were applied to each element. Both hills and valleys were found to have similar effects.;A two-dimensional model of a valley with a Gaussian cross-section was constructed. Piezo-electrical transducers were used to generate elastic waves. The signals were recorded and processed digitally to provide superior quality amplitude measurements. The transfer function measured on the model is lower than that predicted by the approximation. The measured dispersion was very close to the predicted values