Vertical-Slice Matched-Field Tomography

This paper describes a broadband tomographic inversion method for estimating geoacoustic parameters in a range-dependent shallow-water waveguide. The technique makes use of acoustic field data from multiple broadband sources obtained on a system of vertical line arrays in the water. The inversion is based on matched-field processing, using ray theory to calculate the replica fields for the range-dependent waveguide in a two-stage inversion process. The first stage uses the amplitude of the first-order bottom-reflected signal paths to estimate bounds for the geoacoustic parameters at the water/sediment interface. The second stage includes the sediment refracted paths and uses a novel pairwise matched-field processor to estimate the full geoacoustic profile with depth. The performance of the inversion is demonstrated in this paper for a vertical-slice geometry consisting of multiple sources and two vertical line arrays. Synthetic data that simulate the environment of a geoacoustic tomography experiment carried out in Haro Strait are inverted to estimate a range-dependent geoacoustic profile for the site.