MIGRATION OF BACKSCATTER DATA FROM THE MID-ATLANTIC RIDGE

In studies of low-frequency reverberation within the marine environmen t, a central concern is the relationship between reverberation events and morphological features of the seafloor. A time-domain migration al gorithm for the reverberation intensity field is developed that produc es scattering coefficient maps coregistered with a bathymetry database . The algorithm is tailored to broadband transient sources with good r ange resolution, and was developed to analyze an extensive set of reve rberation records from a 200-255 Hz source collected on the flanks of the Mid-Atlantic ridge. The precise, sample-by-sample, tracking of wav efronts across elements of the bathymetry database that forms the foun dation of the algorithms implementation results in reverberation maps that show a clear and detailed correlation between scattering and morp hology with narrow scarp slopes consistently highlighted. Environmenta lly induced asymmetries in transmission loss and incidence angle are e xploited to break the inherent left-right ambiguity of the receiver ar ray. Iterative migration, assuming a dominant dependence of backscatte r on grazing angle, produces images, even from individual records, tha t show good ambiguity resolution. Results from multiple records corrob orate the effectiveness of the ambiguity resolution and demonstrate th e stability of the scattering coefficient estimates and the acoustic s ystem. (C) 1998 Acoustical Society of America.