Acoustic Imaging of Subsurface Features

The characterization of sites containing buried hazardous wastes and the selection of new waste disposal sites have become important problems for environmental engineers. Because of the potential risks associated with uncertainty of the subsurface environment, increasing effort has been dedicated to application of available remote sensing techniques. One such technique which is quantitative and offers high resolution is geophysical tomography (GT). Two approaches to GT are examined: backprojection, which traces straight ray paths, and backpropagation, which inverts the wave equation. Results of field studies demonstrate that buried inclusions having length scales on the order of 0.5 m can be resolved using GT and that identification of differing buried waste forms is possible. This method has been successfully demonstrated for a number of applications and shows great promise for many more.