Acoustic Properties of Marine Sediments: Impact of Granular Packing Structure

We use discrete element method (DEM) simulations to explore the frequency-dependent phase speed and attenuation of acoustic propagation through dissipative granular materials. Wave propagation in geophysical environments often involves propagation through fluid-saturated or dry granular materials, but models to explain observed scalings are lacking, including explanations of underlying physical mechanism. We model acoustic propagation through granular packings, using both Hookean and Hertzian contact laws with and without damping, allowing for analysis of energy loss mechanisms. We find that attenuation depends not only on the frequency of the driving oscillation but also on the pressure of the system, with lower pressures exhibiting greater scatter in both transverse and longitudinal wave components. Moreover, even in the absence of damping, attenuation persists through scattering, which is a novel mechanism for acoustic attenuation in these systems.