Multi-Frequency Inversion of Synthetic Transmission Loss Data Using a Genetic Algorithm

The organizers of the Benchmark Workshop for Geoacoustic Inversion Methods (Vancouver, June 1997) produced in advance several sound propagation scenarios, simulated using the wavenumber integration model SAFARI. The simulated pressure fields were made available to all interested, while several key geoacoustic properties of their environments were kept secret. For a number of these test cases we have applied Matched-Field Inversion to determine the unknown geometric and geoacoustic parameters. A Genetic Algorithm has been used together with the normal-mode model MODELOSS as a forward model. The parameters from the benchmark tests, which the forward model was most sensitive to, were well determined in this way (water depth, source depth and range, the attenuation in the sediment layer and the velocity in the upper part of the layer). The less influential parameters were not found with the same accuracy and were often not reliable. The density in the basement may have been just a random choice.