For almost a decade the Marine Physical Laboratory of Scripps Institution of Oceanography has been conducting near-bottom geophysical surveys involving quantitative seismic profiling. Operating initially at 4 kHz and more recently at 6 kHz, this system has provided a wealth of fine scale quantitative data on the acoustic properties of ocean sediments. Over lateral distances of a few meters, 7-dB changes in overall reflected energy as well as 10-dB changes from individual reflectors have been observed. Anomalously high amplitudes from deep reflectors have been commonly observed, suggesting that multilayer interference is prevalent in records from such pulsed cw profilers. This conclusion is supported by results from sediment core physical property work and related convolution modeling, as well as by the significant differences observed between 4- and 6-kHz profiles. In general, however, lateral consistency has been adequate in most areas surveyed to permit good estimates of acoustic attenuation from returns from dipping reflectors and sediment wedges.
