Surface-wave dispersion computations for perfectly-elastic media are generalized to allow dispersion-attenuation computations for anelastic media. In each layer, frequency-dependent, body-wave phase velocity and attenuation are taken into account directly. For a 50-layer structure, a single Love-wave dispersion-attenuation point can be determined in 0.28 sec—the phase velocity containing about 16 significant figures and the phase attenuation about 14, where 16 decimal digits are used in computations on an IBM 360/91 computer. Accuracies of 7 significant figures can be obtained in 0.13 sec. To this latter accuracy, the determination of the Love-wave dispersion and attentuation for an anelastic structure takes about 6.8 times the amount of computation time required to compute the dispersion for the comparable perfectly-elastic structure.
The technique is applied to Love waves on an anelastic, radially heterogeneous sphere. A family of low-velocity zone channel waves is identified and investigated. A possible explanation for the disappearance of Lg across large oceanic paths is offered.