Matched-field geoacoustic inversion in a range-varying waveguide

Abstract

In recent years, geoacoustic inversion methods based on matched-field processing concepts have been devised for inferring the sub-bottom properties of shallow-water waveguides using measurements of acoustic signals received on hydrophone arrays. The development of these matched-field inversion (MFI) procedures is driven by two goals: (1) to obtain an accurate geophysical description of the morphology of the sub-bottom structure, and (2) to characterize the acoustic response of the sub-bottom so that its effect on sound propagation can be predicted. Knowledge of (2) can improve the effective ranges for using sound in underwater communication and/or source localization applications. Of practical interest is the question: How crude can our estimates of the sub-bottom structure be and still allow successful acoustic source localization using model-based signal processing methods? In this paper, a hybrid simplex simulated annealing MFI code [M. R. Fallat and S. E. Dosso, J. Acoust. Soc. Am. 105, 3219–3230 (1999)] is combined with a high-order parabolic equation (PE) model and applied to geoacoustic inversion in a shallow-water waveguide whose sub-bottom properties vary with range. In particular, we investigate simple sub-bottom characterizations for some test cases considered recently at the Inversion Techniques Workshop held in Gulfport, MS. a)Presently on exchange from the Defence Science and Technology Organisation, Australia.