Range-dependent matched-field inversion of SWellEX-96 data using the downhill simplex algorithm

Matched-field inversion (MFI) techniques have been applied for effective an d efficient estimation of geoacoustic parameters of the ocean bottom. This paper presents a new tomographic MFI method for use in range-dependent envi ronments. The MFI correlates modeled data with measured data and uses a sea rch algorithm to determine model parameter values that maximize the correla tor. In the present method, a parabolic equation propagation model is used to compute replica fields to account for mode coupling in the environment. The search algorithm is a two-stage hybrid method that combines an initial global component and a final local component. The first stage employs a ran dom search to determine NS 1 parameter sets with the best correlations, whe re N is the number of parameters being determined. In the next stage the N + 1 sets are used as inputs to the local downhill simplex algorithm. The al gorithm is shown to perform well for simulated vertical line array data for an environment representative of the SWellEX-96 experimental site. The inv ersion technique is then applied to measured data obtained from a radial tr ack in SWellEX-96. The geometric parameters of. the experiment and dominant geoacoustic parameters were successfully recovered for data with relativel y low signal-to-noise ratio. (C) 1999 Acoustical Society of America.