ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2aAO4. Adaptation of genetic-algorithm search for matched-field inversion of ocean bottom compressional wave speed profiles.

Thomas J. Hayward

T. C. Yang

Naval Res. Lab., Washington, DC 20375-5350

Matched-field inversion for ocean bottom compressional wave speeds using a synthetic horizontal aperture has been demonstrated previously in simulations and data analyses employing optimization by simulated annealing [M. Collins, W. Kuperman, and H. Schmidt, J. Acoust. Soc. Am. 92, 2770 (1992)] and genetic-algorithm search [P. Gerstoft, J. Acoust. Soc. Am. 95, 770 (1994)]. The first reference noted a lack of sensitivity of the matched-field ambiguity function to zero-mean functional variations of the sound-speed profile. This lack of sensitivity sometimes results in slow convergence of the search algorithm when applied to profiles with several unknown parameters. This problem is observed in simulations using genetic algorithm search. Improved convergence of the genetic algorithm is then achieved by using some nonstandard procedures, including autologous gene exchanges, to generate new solutions. The simulations indicate the practical feasibility of inversion for deep-bottom (up to 500 m) compressional wave speeds at a shallow-water site using a single receiver and coherent synthetic horizontal aperture processing of a towed-source signal.