Abstract:
A number of useful applications for matched-field inversion have been envisioned for the littoral zone. These include the estimation of environmental parameters, such as the sound-speed structure of the water column and geoacoustic properties of the sediment, as well as the more traditional localization of submerged objects. However, natural disturbances such as passing surface and internal gravity waves often place shallow-water waveguides in such a state of flux that a signal, deterministic when transmitted from a source, becomes fully randomized after propagating only several channel depths away in range to a receiver. When not properly accounted for, such randomization can severely degrade the accuracy of a matched-field inversion, which presumably is for parameters that remained fixed during the measurement process. Therefore, the general performance of a matched-field inversion is examined from the perspective of statistical estimation, under the worst case scenario of a waveguide that may be fluctuating rapidly during a given transmission or set of transmissions. Specific examples for shallow-water matched-field tomography and object localization using ambient noise are then considered.