Range-dependent geoacoustic inversion: Results from the inversion techniques workshop

Model-based geoacoustic inversion in range-dependent underwater environments is a challenging task constrained by data quality (synthetic or measured) and propagation-model efficiency and accuracy. The Inversion Techniques Workshop (ITW), held in Gulfport, MS, May 15-18, 2001, was organized for the acoustics community to present state-of-the-art numerical geoacoustic inversion capabilities in range-dependent shallow-water environments. The organizers defined five range-dependent test cases (three synthetic and two experimental cases). Two of the synthetic cases were adopted for geoacoustic inversion in this paper. The first test case (TC1) is a monotonic down-slope bathymetry problem and the adiabatic normal-mode model PROSIM was applied for the inversion in this case. The second test case (TC3) is a flat-bottom case with an intrusion. The forward model used in this case was RAMGEO. The global optimization package SAGA was used for geoacoustic inversion of the synthetically generated reference solutions for TC1 and TC3. In general, the geoacoustic inversion results are in good agreement with the true solutions provided by the organizers. The results obtained demonstrate the feasibility of performing geoacoustic inversion in synthetic range-dependent shallow-water environments. However, results show that the propagation model choice in the inversion is strongly dependent on the specific range-dependent environment.