A comparison of two modeling approaches for reverberation in a shallow-water waveguide where the scattering arises from a sub-bottom interface

Abstract

In shallow water environments with a low-speed sediment layer overlying a higher-speed sub-bottom, the observed reverberation may be dominated by scattering from the sub-bottom. Here, reverberation predictions from normal mode and energy flux models are compared for the case where the scattering arises from a sub-bottom half-space under the low-speed sediment layer. It is shown that in such an environment, the position of the angle of intromission, in addition to the angular dependence of the scattering kernel, is a factor controlling the vertical angle distribution. It is also shown that the reverberation from a sub-bottom horizon is typically governed by higher grazing angles than the case where the scattering occurs at the water-sediment interface. There was generally very close agreement between the models as a function of frequency (200–1,600 Hz), layer thickness (0–8 m), and range (1–15 km). The model comparisons, showing some differences, illuminate the effect of different approximations in the two approaches. [Work supported in part by the Office of Naval Research.]