Modelling reconstruction and boulder size-frequency distribution of a young (< 5 Myr) landslide located in Simud Vallis floor, Mars

We focus on a young (similar to 4.5 Ma), 3.4 km long landslide located in the floor of Simud Vallis, Oxia Palus Quad-rangle of Mars. By making use of a 2 m-scale HiRISE DEM we reconstruct the terrain surface before the landslide and in doing so we estimate the release and deposition heights and volumes related to the different stages of the landslide. Using the r.avaflow software we simulate the mass movement as a multi-stage event, and obtain simulated deposits that are both spatially and longitudinally comparable to the current landslide deposits. Through two 0.25 m-scale HiRISE images we identify and manually count > 130,000 boulders that are located along the landslide, deriving their size-frequency distribution and spatial density per unit area for boulders with an equivalent diameter >= 1.75 m. Our analyses reveal that the distribution is of a Weibull-type, suggesting that the rocky constituents fractured and fragmented progressively during the course of the mass movement, consistent with our proposed two-stage model of landslide motion.