S. E. Dosso
N. R. Chapman
Defence Research Establishment Pacific, FMO Victoria, BC V0S 1B0, Canada
R. G. Racca
N. G. Henson
Jasco Research Ltd., Brentwood Bay, BC V8M 1P7, Canada
Matched-field inversion for source location, environmental properties, or a combination of the two (focalization) is based on comparing measured acoustic fields to replica fields predicted for a variety of possible environmental parameters and/or source positions using a numerical propagation model. Although this approach is conceptually straightforward and widely applicable, it requires a large number of replica-field computations and can be impractically slow if the propagation modeling is not carried out in an efficient manner. This is particularly true for environmental inversion and focalization where the expanded parameter search space generally requires a very large number of replica field computations, even if a relatively efficient optimization algorithm such as simulated annealing (SA) is employed. This paper describes matched-field inversion for geoacoustic properties using SA and rapid acoustic-field modeling. The replica-field modeling is based on the normal mode solution and makes use of multivariate interpolation of precomputed ``look-up'' tables of modal quantities stored as a function of the geoacoustic parameters. The optimum grid-element size for the modal tables is considered, and two interpolation schemes, linear and Shepard's method (locally quadratic), are investigated. An example is given of geoacoustic inversion in a North Pacific environment.