Matched-Field Inversion is often used to determine seabottom parameters in a shallow water waveguide from measurements of the acoustic field. The estimates of the parameters obtained using this method are very sensitive to mismatch between the water depth used in the model and the actual water depth. It is therefore difficult to achieve robust parameter estimates. This paper describes a method that separates the part of the acoustic field that is less sensitive to the water depth (the low order modes) from the part that is more sensitive and hence causes the mismatch problem (the higher order modes). The measured variation of horizontal wavenumber with frequency for the low order modes, the dispersion curves, are used in a matched-field type algorithm to estimate the required parameters with much reduced sensitivity to water depth mismatch. Because this technique matches theoretical (model-based) and measured dispersion curves it is called Matched Dispersion Curve Inversion. It is inherently multi-frequency and, in theory, can invert for any parameters that affect the seabed reflection coefficient. Moreover, the technique is independent of source and receiver depth, and the necessary measurements easily made by Hankel transforming the acoustic pressure measured over a horizontal line array of hydrophones.
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