Catastrophic tailings dam breaches can generate runout events that challenge conventional geotechnical and hydrotechnical runout modelling approaches. This study presents a back-analysis of the Las Palmas tailings dam breach that was triggered by the Mw 8.8 Chilean (Maule) earthquake on February 27, 2010. To evaluate the failure, 2D plain-strain back-analysis was performed using the open-source Anura3D software. The MPM models focus on post-liquefaction kinematics rather than the cyclic pore-pressure generation triggering mechanism and adopts the Mohr–Coulomb failure criterion with liquefied zones assigned an undrained residual strength. The case history simulations demonstrate some of the benefits of MPM for modelling for non-uniform, multi-phase runout events, namely, its ability to reproduce the interpreted flow behaviour of the Las Palmas runout events which included suspension of unsaturated tailings over liquefied basal layer and bulldozing of frictional dam-fill at the runout front. MPM overcomes some of the limitations of depth-averaged methods and shows promise for estimating breach kinematics (displacements and velocities).