Estimation of geoacoustic parameters of the ocean bottom by inversion of reflection loss data
Date
1995
Authors
Hannay, David Edward
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Abstract
An inversion method has been developed for estimating the geoacoustic parameters of the ocean bottom at thin sediment sites, such as those in the Abyssal Hills region of the North Pacific The ocean bottom is modeled by two elastic layers representing pelagic sediment overlying basalt The method fits bottom reflection loss versus grazing angle, calculated for many possible bottom models, to measured data Simulated annealing optimization is used to perform an efficient search to find the model which produces the best match between the calculated losses and the data Parameter values associated with this optimum model are taken as the geoacoustic parameter estimates at the experiment site This method was tested with simulated data to demonstrate Its effectiveness for estimating several elastic parameters The method was found to provide reliable estimates for basalt p and s wave speeds, and the sediment s wave speed The inversion method was applied to data obtained along a track in the North Pacific, over which the basalt age increased from -42 m y to -63 m y The estimates indicated trends of increasing basalt wave speed with age, from 26 km/s to 32 km/s for p waves, and from 10 km/s to 15 km/s for s waves