Accession Number : ADA320152

Title :   Migration of Backscatter Data from the Mid-Atlantic Ridge.

Descriptive Note : Final rept. 1 May 89-30 Sep 95,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA INST OF GEOPHYSICS AND PLANETARY PHYSICS

Personal Author(s) : Harding, Alistar J. ; Hedlin, Michael A. ; Orcutt, John A.

PDF Url : ADA320152

Report Date : 10 JAN 1997

Pagination or Media Count : 21

Abstract : In studies of low-frequency reverberation within the marine environment, a central concern is the relationship between reverberation events and morphological features of the seafloor. A time-domain migration algorithm for the reverberation intensity field is developed that produces scattering coefficient maps coregistered with a bathymetry database. The algorithm is tailored to broadband transient sources with good range resolution, and was developed to analyze an extensive set of reverberation records from a 200-255 Hz source collected on the flanks of the Mid-Atlantic Ridge. The precise, sample-by-sample, tracking of wavefronts across elements 9f the bathymetry database that forms the foundation of the algorithms implementation, results in reverberation maps that show a clear and detailed correlation between scattering and morphology, with narrow scarp slopes consistently high- lighted. Environmentally induced asymmetries in transmission loss and incidence angle are exploited to break the inherent left-right ambiguity of the receiver array. Iterative migration, assuming a dominant dependence of backscatter on grazing angle, produces images, even from individual records, that show good ambiguity resolution. Results from multiple records corroborate the effectiveness of the ambiguity resolution and demonstrate the stability of the scattering coefficient estimates and the acoustic system.

Descriptors :   *BACKSCATTERING, *MIGRATION, *ACOUSTIC SCATTERING, DATA BASES, ALGORITHMS, TRANSIENTS, SOURCES, SCATTERING, ENVIRONMENTS, MORPHOLOGY, RESOLUTION, INTENSITY, ARRAYS, TRACKING, ESTIMATES, BATHYMETRY, ASYMMETRY, COEFFICIENTS, RECEIVERS, STRENGTH(GENERAL), BROADBAND, MAPS, RECORDS, ACOUSTIC EQUIPMENT, ATLANTIC OCEAN, ANGLE OF INCIDENCE, REVERBERATION, ITERATIONS, AMBIGUITY, TIME DOMAIN, OCEAN ENVIRONMENTS, ROUGHNESS, ACOUSTIC DATA, LOW FREQUENCY, DETERMINANTS(MATHEMATICS), OCEAN BOTTOM, WAVEFRONTS, TRANSMISSION LOSS, OCEAN RIDGES, GRAZING ANGLES.

Subject Categories : Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE