Geoacoustic parameter estimation using back-wave propagation technique

The concept of back-wave propagation(BWP) is developed as an inversion meth od to estimate geoacoustic parameters of the ocean bottom from measurements of the acoustic field for a known source-receiver geometry. A phase-regula ted technique is introduced to measure the sensitivity of the BWP inversion method for estimating weakly sensitive geoacoustic model parameters. The p aper demonstrates theoretically that the sensitivity can be measured by a s ensitivity factor a using the phase-regulation procedure. The paper also de monstrates that the spatial resolution of back-propagared signal energy tha t is focused at the known source location is increased when a increases. Th is result leads to the definition of a criterion based on the spatial distr ibution of the signal energy around the source location. The criterion is f ormulated based on the spatial variance of the back-propagated pressure fie ld in a window around the known source location. This technique is applied to data from the Pacific Shelf experiment that was carried out in shallow w ater off the west coast of Vancouver Island in the Northeast Pacific Ocean. Use of the BWP inversion method is demonstrated for estimating the geoacou stic model parameters, including water depth, compressional speed of the se diment layer, and sediment density.