Sediment sound speed inversion at low frequencies in shallow water

Abstract

A direct method previously developed for shallow water inversion is presented here along with the assumptions for its convergence and improvements for the solution of a more complex inverse problem. The method estimates sediment sound speed and follows discontinuities as the sediment layer properties change. Sediment thickness is also calculated. The approach is fast in contrast to other techniques that navigate a multi-dimensional search space. Implementation requires low-frequency measurements at a horizontal array and a source anywhere in the water column with only the continuous spectrum available. Several assumptions are made which appear restrictive at first but can be eventually relaxed. Although the approach was first developed considering a constant density profile, we show how realistic density profiles can be considered. [Work supported by ONR.]