Broadband inversion of shallow-water range-dependent acoustic data using a genetic algorithm

Abstract

In October 1997, shallow-water experiments were carried out on the Bank of Adventure southwest of Sicily. The purpose of this trial was to obtain acoustic data in range-dependent environments for testing and further developing matched-field inversion methods to determine geoacoustic properties of the sea floor. On one track of the experiments, an acoustic source was towed over a sloping bottom with a water depth varying from 100 m at the vertical receiving array to 75 m at the end of the 7-km track. The array comprises 64 hydrophones and covered the central 62 m of the water column. At several source-receiver ranges, the source (towed below the thermocline) transmitted a multitone signal in the band 50–300 Hz. Detailed sound-speed profiling of the water column and seismic profiling of the bottom were performed along the track. Broadband inversion of the acoustic data was done using a genetic algorithm as the global search method. The forward model uses standard adiabatic mode theory. Inversion results are shown for different geoacoustic models with different complexity concerning sediment layering. The bottom parameters obtained agree well with the results of the seismic analysis and its geological interpretation.