Particle-resolved simulation of sediment transport over vibrating beds

Sediment transport caused by large earthquakes produces distinctive deposits that help extend our records of these events. To understand the underlying mechanisms of seismically induced sediment transport, we perform particle-resolved simulations of sediment transport over vibrating beds, with earthquake vibrations modelled as sinusoidal horizontal and vertical oscillations. The simulations fully resolve both the carrier flow and the motion of individual grains, and phase-averaged statistics are used to characterise how oscillations modulate turbulence, stress and sediment motion. Analysis of the sediment-transport rate and its phase-averaged decomposition shows a rhythmic response to oscillations, enhanced transport, changes in the thickness of the mobile layer and episodes of bidirectional motion occurring during specific phases of the forcing. Our findings on the influence of oscillation conditions on sediment motions provide mechanistic insight in support of the idea that large earthquakes can induce sediment transport even on flat surfaces.