ASA 127th Meeting M.I.T. 1994 June 6-10

1pUW7. Analysis of North Atlantic bottom reverberation and examination of broadband effects.

Kevin B. Smith

William S. Hodgkiss

Marine Phys. Lab., Scripps Inst. Oceanogr., Mail Code 0704, La Jolla, CA 92093-0704

High-quality experimental data were collected during the 1994 ONR-Bottom Acoustic Reverberation SRP cruise. Preliminary analysis with a cw PE solution shows good correlation between ensonification and reverberation. A broadband version of the UMPE model computes the time/depth domain solution at any given range. The presence of incoherent forward scatter is evident for various locations within the SRP Natural Laboratory in the vicinity of the mid-Atlantic ridge east of Bermuda using a 200x200-m gridded bathymetry database derived from a previous SRP geophysics cruise. By storing most of the range dependence of this solution, a transformation can be made to a complete set of time snapshots or ``time fronts.'' This analysis animates the pulse propagation through physical space and introduces new insights to the understanding and interpretation of bottom reverberation. A further extension of the BB-UMPE model provides a study of the frequency dependence of reverberation relative to small (~(lambda)) bottom roughness correlation length scales. [Work supported by ONR, Code 3240A.]