Altan Turgut and par Stephen N. Wolf
Naval Res. Lab., Acoust. Div., Washington, DC 20375
Genetic algorithms are used to invert statistical properties of sea bottom/sub-bottom from backscattering data. Backscattering from the seabed is calculated using composite roughness model of Jackson et al. [J. Acoust. Soc. Am. 79(5) (1986)], incorporated with the volume scattering model of Stockhausen [NRE Report 63/9 (1963)]. A parametric study indicates that, for given average sound speed and density of the seabed, bottom roughness parameters such as spectral strength and spectral exponent and sub-bottom parameters such as sound-speed variation, vertical correlation length, and horizontal correlation length can be inverted successfully. Complementary sub-bottom measurement techniques such as core sampling, seismic, and tomographic measurements are also discussed. Acoustic calculations using measured seabed inhomogeneities predict significant coupling to the higher-order modes. This coupling manifests itself as an important loss mechanism.