Analyzing Avalanche Patterns on a Conical Bead Pile

A conical bead pile is used as a model critical system to investigate granular avalanches and criticality. The pile is roughly 20,000 beads, each 3 mm in diameter, and the system is driven by dropping one bead at a time onto the apex of the pile. This research focused on the size and frequency of avalanches in the system. We studied how closely our avalanche system follows the geophysical earthquake model Omori's law, which states that the frequency of smaller events follow a power law distribution before and after the earthquake mainshock. Three different avalanche analysis routines were created to study the frequency of avalanches over any given run, and how the frequency varies over the course of a run. The first algorithm picks out the largest avalanches in the system within a specific interval and sets these as the "main avalanches" in the run. The second analyzes how many avalanches occur between two main avalanches and calculates the probability of an avalanche occurring in general during a given interval. Finally we find the avalanche occurrence rate in an interval immediately preceding and following each main avalanche. The optimal threshold size for a main avalanche and the length of the relevant pre-/post-avalanche time interval are being determined. We present preliminary results on the size of main avalanches in relation to how many avalanches occurred overall and in relation to the frequency of avalanches in the interval preceding and following the main avalanches.