Matched beam processing for geoacoustic inversion of bottom sound-speed profiles

Abstract

A broadband signal (shot) received on a vertical array was processed for geoacoustic inversion of bottom sound-speed profile. The data were beamformed to show the distribution of waterborne and bottom interacting signals. By correlating the (complex) beams containing the bottom interacting signals with the equivalently formed beams for the replica field (matched beam processing), one evaluates the ambiguity function maximum at the source location and searches for the bottom sound-speed profile which yields the highest correlation for the matched beam processing. Different frequency bands of the signal are investigated to evaluate the sensitivity to bottom sound-speed variations. The inverted sound-speed profiles are found consistent (within the resolution of 50–100 m/s) with the sound-speed profiles estimated from (1) core samples and other geoacoustic data at the site, and (2) the arrival time of the Head waves [J. Wolf, J. Acoust. Soc. Am. 94, 1769 (1993)].