Effects of non‐welded interfaces on guided SH‐waves

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.