Interface scattering from broadband sources in the New England Mud Patch

The New England Mud Patch (NEMP) has been a region of interest in underwater acoustics for the past decade. Numerous geo-acoustic inversion methods have been used to estimate the compressional and shear wave speeds, and densities of four distinguishable sediment layers. While exact values vary, it is known that the upper-most layer is a relatively thin, fluid-like layer (layer 1) of mud. Below that lies more rigid mud (layer 2) that has varying physical properties with depth, followed by a sand layer (layer 3) of approximately 10 m. Below these sediment layers, an elastic half-space layer is assumed for modeling purposes. The Seabed Characterization Experiment (SBCEX22) utilized Ocean Bottom Recorders (OBX’s) to provide acoustic and seismic measurements taken at the water–sediment interface. The resulting acoustic pressure and particle velocity measurements indicate the presence of frequency dependent reverberation, likely from roughness at the mud-sand interface between layer 2 and layer 3. Analysis of the shear potential in the elastic layers of the seabed suggests that the frequency dependency seen in these data can be attributed to bottom loss from shear effects. Data from the NEMP and modeling results from a wavenumber integration model will be shown.