Influence of geoacoustic modeling on predictability of low-frequency propagation in range-dependent, shallow-water environments

Abstract

In a previous study of predictability of relative intensity and horizontal wave numbers by the authors, parabolic approximations were used in range-independent shallow-water waveguides. Uncertainties in sediment properties were found to be the most significant factor limiting prediction accuracy. In this paper, models of bottom sound-speed profiles that take into account sediment consolidation are developed, and their effects on propagation model predictions in range-dependent environments are examined. Modeling of low-frequency results from a New Jersey shelf experiment is the focus of our efforts. Using borehole data and Biot–Stoll theory, the porosity profiles for homogeneous consolidated sediments are derived, and corresponding sound-speed profiles for different sediment types are then constructed. Predictions from models with consolidated sediment layers throughout the bottom are compared with results from cases where bottom sound speed is comprised of piecewise linear segments. In addition, bottom sound-speed range dependence is shown to be significant in the area of the experiment, and different geoacoustic models for it are examined. Comparisons of experimental data with model predictions incorporating range dependence are illustrated and show the influence of the bottom model.