These are also known as surface waves. Surface shear waves are polarised in the plane of the surface because that is the only axis of vibration available.
One type of surface wave is the Rayleigh wave. This wave takes the form of an elliptical wave. The Rayleigh wave is a mixture of shear and longitudinal waves. It is sustained from reflections of acoustic waves on and beneath the surface. This system is analogous to fibre optics, where light is guided along a glass fibre by reflections with an angle less than the critical angle of the material.