Note on the variational and homogeneous layer approximations for the computation of Rayleigh-wave dispersion

An earlier study of upper mantle structure using a variational method is repeated using the homogeneous layer approximation programmed for an electronic digital computer to obtain dispersion curves. The dispersion curves computed by the two methods differ significantly but systematically so as to yield the same conclusion about the presence of the Gutenberg low-velocity zone in the upper mantle.