Observation and inversion of surface-wave dispersion

Rayleigh wave phase velocities have been measured to periods in excess of 160 sec for a number of profiles, worldwide and for many different geologic structures. It is found that at least five structural provinces must be established; these include shields, aseismic continental platforms, rifts, ocean basins, and mountains. The inversion of these profiles shows that the shields probably have a little or no low-velocity channel in the mantle, the aseismic platforms have a low-velocity channel with high contrast to a thick lid, the oceans have a high-contrast channel and a thin lid, the rifts have low-velocity material but probably without a lid. Comparison is made between regional observations and the great-circle decomposition methods for determining phase velocities in type regions.