MEASUREMENT AND LOCALIZATION OF INTERFACE WAVE REFLECTIONS FROM A BURIED TARGET

It is demonstrated that seismic interface waves on the surface of a na tural beach can be used to identify the position of a buried object. F or this experiment, the waves were created with a sediment-coupling tr ansducer and received on a three-element horizontal line array of tria xial geophones. The source and its coupling to the medium provided a h igh degree of signal repeatability, which was useful in improving sign al-to-noise ratio. Reception of all three directions of particle veloc ity made it possible to augment conventional beamforming techniques wi th polarization filters to enhance interface-wave components. Reverber ation in the beach was found to be large, though, and coherent backgro und subtraction was required to isolate the component of the sound fie ld reflected by the target. Propagation loss measurements provided com parisons of reflected signal power with predictions made previously, a nd the two were found to agree closely. (C) 1998 Acoustical Society of America.