Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1995The data analysis of a deep-sea bottom backscattering experiment, carried out over a
sediment pond on the western flank of the Mid-Atlantic Ridge in July 1993 with a 250-
650 Hz chirp source and a vertical receiving array suspended near the fiat seafloor,
is presented in this thesis. Reflected signals in the normal incidence direction as
the output of endfire beamforming are used to determine the sediment structure.
The sediment is found to be horizontally stratified, except for two irregular regions,
each about 20 m t hick, located around 18 m and 60 m beneath the water-sediment
interface. Multiple constraints beamforming is shown to be effective in removing
coherent reflections from internal stratified layers, which is critical to the analysis of
bottom backscattering. With backscattered signals obtained by beamforming, the
above-mentioned two inhomogeneous regions are found to be the dominant factors on
the bottom backscattered field, both in the normal incidence and oblique directions.
The backscattering strength as a function of grazing angle is estimated for each of
the two regions
