Discrete element method simulations for acoustic propagation through idealized seafloor sediments

Abstract

We performed discrete element method (DEM) simulations for the propagation of pressure and shear waves in idealized seafloor waveguides. Preliminary simulations used identical spheres configured in a random loose pack. DEM waveguides were essentially one-dimension with a 10 by 10 grain diameter cross section and varied in length from 20,000 to 100,000 grain diameters for grains ranging from 0.2 to 0.5 mm in diameter with the material properties of quartz. Rough walls were placed at the ends of the waveguide and periodic boundaries were used in the lateral direction. Pressure and shear wave propagation was simulated through normal and tangential sinusoidal oscillation of the boundary wall at frequencies ranging from 100 to 1,000 Hz. Sensitivity of propagation speed and attenuation to the specification of the material properties of the grains was investigated. For example, our simulations demonstrate the well-known dependence of pressure wave propagation speed on grain stiffness. Discussion will focus on creating links between simulation results and continuum models for acoustic propagation in seafloor sediments.