### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 2aUW8. A rapid forward model for matched-field inversion.

**R. J. Cederberg
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Michael D. Collins

**
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*Naval Res. Lab., Washington, DC 20375
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The forward model is an important component of a matched-field inversion
algorithm. The forward model must be efficient because it is often necessary to
compute a large number of replica fields during the parameter search. An
efficient forward model will be described for an experimental configuration
involving a source and a vertical array separated by up to several tens of
wavelengths in range. The operators of the self-starter and the split-step Pade
solution are combined into a single operator that acts on a delta function to
give the field on the array. On a parallel-processing computer, this approach
provides the replica field in the computation time it takes to solve a single
tridiagonal system in a conventional parabolic equation algorithm. This
efficiency gain is not achieved by sacrificing accuracy. The approach typically
involves the solution of about ten tridiagonal systems. Finite-difference based
separation of variables solutions typically require the solution of hundreds or
thousands of similar tridiagonal systems. The efficiency of the rapid forward
model will be demonstrated for the matched-field inversion problem of
estimating the parameters of the ocean bottom.