Acoustic Wave Dispersion and Scattering in Complex Marine Sediment Structures

: The long term science goals are to understand and quantify the physical mechanisms that control propagation and scattering in the seabed. The objectives are to advance understanding of 1) the nature and mechanisms leading to sediment volume scattering and 2) the effects of shear waves in general layered media. These advances will provide the basis for measuring dispersion in in-situ sediments in the frequency range of interest, 0.1-10 kHz. This work builds on prior research in disentangling the effects of sedimentary layering and sound speed/density gradients [1]. The approach includes both theoretical as well as measurement components. Theory is needed to better understand the relationship between sediment volume scattering from a continuum (e.g., slumps and slides) versus scattering from discrete particles (e.g., rocks, shells, or bubbles). Measurements are needed to 1) exploit the volume scattering theory for identification of the dominant mechanisms and seabed features that give rise to volume scattering and 2) to quantify the effects of various mechanisms, including volume scattering and shear waves on dispersion in marine sediments. The first step will be development of the theory.