An Inverse Method for Obtaining the Attenuation Profile and Small Variations in the Sound Speed and Density Profiles of the Ocean Bottom

Abstract

An inverse method is presented for the determination of the compressional wave speed, compressional wave attenuation, and density as a function of depth for a horizontally stratified ocean bottom. It is based on a perturbation technique for which the required input information is the plane-wave reflection coefficient of the bottom as a function of incident angle at a fixed frequency. The reflection coefficient is related to variations of the acoustic properties about known reference values through a nonlinear integral equation which is then linearized using the Born approximation. An acceptable stable solution of the integral equation is obtained using a priori constraints on the solution. Resolution of the solution obtained is studied using the resolving power theory of Backus and Gilbert1. Examples of inversions using synthetic data are presented using noise-free and noisy data. Results obtained with noise-free data show good agreement between true and reconstructed profiles. Inversions performed with noisy data yield stable, acceptable results.