ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4pUW9. Bistatic reverberation from an ocean ridge.

Nicholas C. Makris

Lilimar Avelino

Richard Menis

Naval Res. Lab., Washington, DC 20375

Bistatic reverberation from a highly lineated ridge in the mid-Atlantic was measured by two research vessels during the ARSRP Main Acoustics Experiment of 1993. Each vessel used a vertical source array and a horizontal receiving array to collect bistatic and monostatic data over a full range of incident and scattered angles with respect to the ridge axis. High-resolution bathymetry reveals that the ridge protrudes above conjugate depth for roughly 50 km, and is characterized by a number of extended scarps running parallel to the ridge axis. Sufficient excess depth exists around the ridge to isolate it with waterborne propagation paths from 1/2 convergence zone (CZ) range (~33 km) where low-frequency returns register precisely with steep scarps. Significant variations in received level from a given scarp occur as a function of incident and scattered angle. The most prominent returns register with scarps facing the receiving array. Registration between returns from high-resolution waveforms (~10 m in range) and fine-scale bathymetry is used to elucidate the fundamental scattering process. Comparisons with monostatic measurements of the same ridge from 1/2 CZ and 2 1/2 CZ indicate how fine-scale structure from a given scarp is smeared in long-range reverberation.