Inversion of geoacoustic profiles in thin-sediment environments from ocean bottom reflection loss data

An iterative inversion method is investigated for estimating the elastic properties of the upper oceanic crust in thin-sediment bottom environments. The method is based on the inversion of reflection loss versus angle data, using simulated annealing to carry out an efficient search over the set of possible models to determine the optimum solution. The cost function in the search algorithm is the rms difference between the measured data and the reflection loss calculated for specific bottom models. The set of model parameters which minimizes the cost function is taken as the best estimate of the geoacoustic profile. The model consists of an elastic-solid sediment layer overlying the basement. In this paper, simulated reflection loss data in a 1/3 octave band centered at 8 Hz are used to demonstrate the importance of modeling the sediment as an elastic solid material in carrying out inversions for thin-sediment (<40 m) environments. Effects of experimental error on the inversion estimates are investigated by introducing random errors onto the simulated data. The parameters found to be least sensitive to experimental errors for this model are the compressional and shear wave speeds in the basement and the shear wave speed in the sediment.<
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