Conventional surface-wave analyses for estimating shallow-seismic properties typically use 2D geometries. A new geometry uses tomographic imaging of surface waves to reconstruct surface-wave velocity and attenuation profiles in three dimensions. Sources and receivers are deployed around a border encompassing an area on the earth's surface. The surface wave is assumed to propagate along a simple ray between source and receiver that attenuates with depth as a function of frequency. Using conventional raypath-tomography techniques, surface-wave velocity and attenuation tomograms can be generated as a function of frequency and then used to estimate shear-wave velocity and attenuation versus depth using standard surface-wave inversion techniques. The methodology is described in a field study designed to image old mine workings. Velocity and attenuation tomograms exhibit anomalous areas that correspond to known voids.

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