A phase regulated back wave propagation technique for geoacoustic inversion

An inversion method based on the concept of back wave propagation (BWP) is described in this paper for estimation of geoacoustic parameters from acoustic field data. A phase-regulation technique is introduced to increase the sensitivity of the method for geoacoustic model parameters having low sensitivity. The case of data consisting of signal plus additive noise is also addressed. It is shown theoretically that the sensitivity can be increased by a factor alpha using the phase regulation procedure, and that the spatial resolution of signal energy that is concentrated by BWP at the known source position is increased when a increases. This result suggests an effective criterion for use in the inversion, based on the spatial distribution of signal energy around the true source location. The basis for the criterion is the spatial variance of the back-propagated pressure field in a window around the known source location. A multistep search process is proposed to avoid using a complicated multidimensional search process. Inversion results from both simulations and experimental data are given. The real data were taken from the Pacific Shelf experiment carried out in shallow water off the West Coast of Vancouver Island in the Northeast Pacific Ocean.