Surface waves under constrained deformation

The possibility of the existence of surface waves in a range of speeds greater than the speed of transverse waves, but smaller than the speed of longitudinal waves is shown. It turns out that, in the boundary value problem for an elastic half-space in this speed range, there are the surface waves whose speed is constant and equal to $\sqrt{2}~b$, where $b$ is the speed of transverse waves. These waves as well as the Rayleigh surface waves have no dispersion. Their speed is determined only by the elastic constants and density of the medium. It is shown that the existence of such a speed is possibly related to the surface waves that appear as unloading waves under constrained deformation.