High resolution geoacoustic inversion using data from a towed broadband source and a bottom moored receiver

Abstract

High resolution geoacoustic models are required for accurate predictions of acoustic propagation and reverberation in shallow water. Our measurement technique employs a towed broadband (400–8000 Hz) source towed near the surface and a moderately deep fixed receiver with source–receiver separations of 0–1000 m. Seafloor reflected data are first processed and inverted in the time domain to get an estimate of interval velocity in each sub-bottom layer. The data are then processed and modeled in the frequency domain to extract sediment layer densities, layer attenuations and velocity gradients. Direct path data are used to calibrate the source. The measurement and inversion technique has been applied at a number of shallow-water sites in the Mediterranean with diverse geo- acoustic properties. The frequency domain processing and modeling techniques will be discussed and the geoacoustic inversion results will be shown for several sites. Azimuthal variability of the geoacoustic models will also be discussed.