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Broadband inversion in the seabed characterization experiment with a moving source

Sequential filtering and linearization for inversion of geometry and sediment parameter estimation in an oceanic environment can be achieved by employing particle filtering and linearization for a single source location. The inversion is here performed with linear frequency modulated signals received at vertically separated phones during the Seabed Characterization Experiment for a source moving towards and away from the receiving array. Short-range measurements allow the identification of some multipath arrivals, whereas others present us with a challenge. The filter, in combination with a simple cross-correlation, acts as a high-resolution estimator, allowing the extraction of four probability densities for arrival times. Arrival times are extracted for each source location. At every location, inversion is performed using the arrival time densities and both linearization and an exhaustive search relating unknown parameters to multiple paths. The results are validated by taking into consideration estimates at neighboring sites. We extract sediment sound speed and thickness assuming both a sound speed gradient and a sediment isovelocity profile and compare the results. [Work supported by ONR.]