Abstract:
A unified model of seabed scattering applicable for a wide low- to high-frequency range is presented. The first-order perturbation solution has been obtained for the scattering amplitude of a randomly inhomogeneous seabed consisting of an arbitrary number of fluid sediment layers having slightly rough boundaries and covering an elastic half-space. The model for the second statistical moments of a scattered field involves both auto- and crosscorrelations between roughnesses of different interfaces as well as between fluctuations of different bulk parameters. Frequency-angular dependencies of the scattering strength for both monostatic and bistatic cases are calculated and analyzed for various seabed types. These dependencies are shown to be largely governed by transitions from one effective seabed type to another. For example, at sufficiently high frequencies, strong absorption causes the influence of stratification to be negligible, while, at moderate frequencies, interference effects due to sediment stratification become important. At lower frequencies, sound penetration of the sediment increases, and the effects of elastic scattering and reflection from the basement supporting both compressional and shear waves and corresponding interference become important. All these effects are considered in the frame of a unified model and their sensitivity to different medium and signal parameters is analyzed. Possible applications are discussed. [Work supported by ONR.]