Effect of a low sound speed sediment layer on seismo-acoustic propagation in the New England Mud Patch

Abstract

The New England Mud Patch (NEMP), located off the coast of Massachusetts, comprises at least four distinguishable sediment layers. The upper-most is a relatively thin, fluid-like layer (1) of mud. Below that lies more rigid mud (2) that has varying physical properties with depth. Below the mud is a sand layer (3) with a thickness of approximately 10 m. Finally, there lies a half-space layer (4) with a significantly higher density and faster compressional and shear speeds. In this paper, we explore the effect of the varying rigidity within the mud layer (2) and the sharp transition at the mud–sand interface, on forward-scattering. In the 2022 Seabed Characterization Experiment (SBCEX22), two different types of broadband sources (SUS and Rupture Disk sources) were deployed. The received signals show evidence of acoustic scattering and the generation of interface waves, along the interface between (1) and (2) and the mud-sand interface between (2) and (3). Results from normal mode modeling using Kraken and seismo-acoustic modeling using OASES suggest that the scattering can be attributed to inhomogeneities in the sediment layers. [Work supported by the Office of Naval Research Code 322OA.]