Statistical distributions of avalanche size and waiting times in an inter-sandpile cascade model

► We characterize the dynamics of an inter-sandpile cascade. ► Avalanches from uniformly-driven sandpile triggers the next layer, and so on. ► Avalanche sizes are seen to evolve from a power-law to gamma distributions. ► We relate the waiting time and size distributions using an analytic model. ► Model results are in agreement with actual data inventories.