Abstract:

A genetic algorithm was used for the inversion of sound speed in the water column and sediment layers south of New England in the Middle Atlantic Bight. The experimental data were SUS charge explosions acquired on a vertical hydrophone array during the Shelf Break Primer Experiment conducted in August, 1996. A genetic algorithm was used to search for optimal parameters in a wide space; the EOF coefficients in the ocean and the compressional sound--speed values in the sediment layers. A range-independent normal-mode routine was used to construct the replica fields corresponding to the parameters. Comparison of group speeds for modes 1--4 and for a range of frequencies from 10--100 Hz was used to arrive at the best parameter fit. A linear perturbative inversion also was done on the same data as described by Rajan et al. [J. Acoust. Soc. Am. 82, 998--1017 (1987)]. This linear method also gives estimates of resolution and variance. Analysis was also done to compute the degree of convergence of each of the parameters. Group speeds for the inverted sound--speed fields provide an excellent match to the experimental data. An efficient hybrid optimization scheme using genetic and linear techniques is presented. [Work supported by ONR.]