The second shear mode of continental Rayleigh waves

Waves of the Rayleigh type corresponding to the fundamental and first shear modes for the continental crust-mantle system have been identified on seismograms previously. In this paper, waves corresponding to the second shear mode are identified for two paths, one from the Belgian Congo to Pietermaritzburg, South Africa; the other from Oklahoma to Palisades, New York. Comparison of the dispersion of these waves with theoretical dispersion for several crust-mantle models demonstrates the increase in resolving power of this method of obtaining crustal structure when data for several modes are available. There are small but measurable differences in the velocity structures averaged along these two paths.