Model-based seafloor characterization employing multi-beam angular backscatter data—A comparative study with dual-frequency single beam

Abstract

Sediment geoacoustic inversion results are estimated employing a multi-beam (MB) echo-sounding system operable at 95 kHz. To characterize the western continental shelf of India (off Goa) seafloor, MB backscatter signals were acquired along with grab sediment samples. The substrate type and roughness of the site were estimated using the composite roughness scattering model with the measured backscatter values. The seafloor parameters, namely mean grain size (M(φ)); roughness spectrum strength (w(2)) and exponent (γ(2)); and sediment volume parameter (σ(2)), for coarse and fine grain sediments are estimated by employing the MB system. These parameters have also been estimated at two other frequencies (33 and 210 kHz) and are compared to the ground truth data to provide sufficient support in validating the model results and increasing the understanding of the shelf seafloor processes. Distinct interclass separations between the sediment provinces are evident from the estimated mean grain size M(φ) and water-sediment interface roughness w(2). The seafloor parameters for coarse and fine grain sediments derived from the 95 kHz MB data are consistent with the sediment sample data as well as with the inversion results obtained using backscatter data at 33 and 210 kHz from the same locations.