Imaging near-surface buried structure with high-resolution surface-wave group-velocity tomography

Often costs or hazardous conditions prohibit geophysical measurements within the survey area. Surface-wave tomography can be a practical method of imaging the near surface shear-wave velocity structure. We demonstrate that this method can resolve meter-size objects. Surface-wave group-velocity travel times along ray-paths through the survey area are determined as a function of frequency by using the "multiple filter" technique of seismic surface-wave analysis. The spatial distribution of group velocities are calculated from the tomographic inversion of the group travel times. Dispersion curves are generated for a selected portion of the survey area and inverted to give shear-wave velocity structure as a function of depth. The buried objects and the disturbance caused by digging are associated with a depression in the shear-wave velocity.