The effects of non-welded interfaces on guided SH-waves are examined analytically and numerically using the displacement-discontinuity model to describe the mechanical shear stiffnesses of the interfaces. A modal solution for guided SH-waves is developed for a layer in non-welded contact with underlying and overlying half-spaces. For low interface stiffnesses, the modal solution degenerates to the SH-plate wave solution and for high interface stiffnesses, to the Love channel wave solution. It is demonstrated that a single non-welded interface separating two half-spaces is incapable of supporting an SH-interface wave.

The effects of interface stiffness on the phase velocities and displacement profiles of guided SH-waves are examined for a low velocity layer in non-welded contact with bounding half-spaces using the modal solution and a numerical boundary integral equation code. The results of this analysis demonstrate that the magnitude of the interface stiffness can have a first order effect on the velocities, amplitudes and displacement profiles of guided SH-waves in a low velocity layer which should make these waves highly detectable in crosshole seismic surveys. ¿American Geophysical Union 1994