Geoacoustic inversion for the Workshop '97 benchmark test cases using simulated annealing

This paper applies simulated annealing matched-held inversion to the Worksh op '97 geoacoustic inversion benchmark test cases. The unknown parameters i n these test cases include various combinations of sediment and basement ge oacoustic properties (layer thickness, compressional and shear speeds, atte nuations, and densities) and geometric parameters (water depth, and source range and depth). The sensitivity of the acoustic field data to the differe nt parameters varies substantially. The simulated annealing inversion devel oped here minimizes a measure of mismatch based on the average Bartlett pro cessor for acoustic data at a number of ranges. The replica pressure fields are computed by summing the modal components provided by an elastic normal mode model, which allows replica fields at multiple ranges to be calculate d efficiently. A total of 15 different geoacoustic inversions are considere d (three realizations each for five test cases). Excellent results are obta ined in a reasonable amount of computation time for all cases. In particula r, the final mismatch values are exceedingly small and relatively sensitive parameters (geometric parameters and sediment properties) are generally es timated to high precision. Relatively insensitive parameters (shear speeds and, in some cases, basement properties) are somewhat less well determined, but generally good estimates are obtained.