Trapping of shear acoustic waves by a near-surface distribution of cavities.

For a halfspace containing random and uniform distribution of empty cylindrical cavities within finite depth beneath the surface, the dispersion spectrum of coherent shear horizontal waves is calculated and analyzed based on the effective-medium approach. The scattering-induced dispersion and attenuation are coupled with the effect of a surface waveguide filled with scatterers. As a result, the obtained spectrum bears certain essential particularities in comparison with the standard Love-wave pattern. Simple analytical estimates enable a direct evaluation of the concentration of scatterers from the dispersion data.