ADJOINT-BASED GEOACOUSTIC INVERSION WITH AN UNCERTAIN SOUND SPEED PROFILE

Abstract: Recently, a numerical extension of the WAPE adjoint-based inversion method has been presented that allows direct inversion of the geoacoustic parameters that are embedded in a discrete representation of nonlocal boundary conditions at the water-sediment interface [Hermand et al., ICTCA 2005]. Uncertainty in the range-average sound-speed profile (SSP) of the water-column section, as typically due to temporal or spatial variability, can significantly degrade the inversion results. The paper discusses an adjoint-based inversion method that includes the SSP as an additional unknown in the parameter space. An a priori estimate of the SSP based on a previous CTD measurement can be efficiently included in an augmented cost function through the use of regularization. By means of adjoint modeling exact gradient information can be obtained to determine the sediment model parameters of the bottom and at the same time adjust for the SSP uncertainty. A case study based on environmental data obtained in Mediterranean shallow waters is used to present first results. 1. MODULAR GRAPH APPROACH On the basis of the analytic adjoint-based optimal control approach that was pro