We extend the formulation of guided waves, in particular, Love and quasi-Rayleigh waves, to obtain information about the elasticity parameters, mass densities and layer thickness from measurements of propagation speeds on the surface. To do so, we formulate the inverse solution to a problem whose input consists of dispersion relations.

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Also, we examine the dispersion relation in the context of a transversely isotropic layer obtained from the Backus average, and compare it to the propagator-matrix approach for individual layers.