### ASA 125th Meeting Ottawa 1993 May

## 5aAO10. Matched-field inversion for range-dependent bottom properties and
source location.

**S. E. Dosso
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J. M. Ozard
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*Defence Res. Establishment, Pacific FMO Victoria, BC V0S 1B0, Canada
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Ocean-bottom properties such as bathymetry and bottom sound speed can be
difficult to measure directly in ice-covered Arctic waters, particularly if
they vary with range. However, inversion procedures hold much promise for
determining range-dependent bottom properties from acoustic measurements. The
inversion is formulated as an optimization problem by assuming a discrete model
of unknown parameters and a bounded search space for each parameter. The
optimization then involves finding the set of parameter values which minimizes
the mismatch between the measured and modeled acoustic fields. Two practical
problems are considered. The first problem involves determining range-dependent
bathymetry and bottom sound speed using a number of sources at known ranges.
The second problem involves source localization when available knowledge of the
bathymetry is inadequate. In this case, the inversion is carried out for source
range and depth as well as bathymetry. Although the bathymetry cannot be
determined uniquely in this manner, an effective bathymetry model can be
computed which allows accurate source localization. This latter case is
essentially an extension of the method of ``focalization'' [M. D. Collins and
W. A. Kuperman, J. Acoust. Soc. Am. 90, 1410--1422 (1991)] to bottom
parameters.