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Abstract. Large subduction earthquakes can rupture the shallow part of the megathrust with unusually large displacements and tsunamis. The long duration of the seismic source and high upper-plate compliance contribute to large and protracted long-period motions of the outer upper plate. The resulting shear stress at the sediment–water interface in, for example, the Mw 9.0 2011 Tohoku–Oki earthquake could account for surficial sediment remobilization on the outer margin. We test this hypothesis by simulating in physical tank experiments the combined effects of high- and low-frequency seismic motions on sediment of different properties (chemistry, grain size, water content, and salinity). Our results show that low-frequency motion during a 2011-like earthquake can entrain several centimeters of surficial sediment and that entrainment can be enhanced by high-frequency vertical oscillations. These experiments validate a new mechanism of co-seismic sediment entrainment in deep-water environments.