Geoacoustic inversion of range-dependent shallow-water data using a complex plane-wave reflection coefficient approach

Abstract

The inversion of range-dependent broadband data in shallow water is presented using a previously developed approach with rays and complex bottom plane-wave reflection coefficients [Stotts, J. Acoust. Soc. Am. 109, 2334 (2001)], allowing separation of seabed physics from water column contributions. Using geometrical optics, waterborne eigenray characteristics are calculated once and stored. Model fields are calculated by including reflection coefficient contributions from each bottom interaction and are evaluated for each perturbation of the seabed properties using simulated annealing to minimize a Bartlett-type cost function. Inversion results from range-independent and -dependent data taken during recent experiments off the coast of Florida are presented using a two-layer model. Implosive source broadband data and XBTs were recorded out to 10 km from a bottom-mounted, 52-element array 229-m deep. Grab samples obtained during the experiment show a thin, hard, crusted surface sediment. Inversions reveal an underlying softer sediment. Model time series using one inverted parameter set are compared to the data obtained from sources at different ranges. Data arrivals are compared to eigenray arrivals providing further propagation insight. Consistent inversion results from other forward models are discussed.