We have investigated the distribution of avalanches which occur when the slope of a sandpile exceeds the metastable slope given by the angle of repose. In contradiction to recent models by Bak, Tang, and Wiesenfeld for the dynamics of granular systems, we do not observe power-law distributions. We also find that the slope of a sandpile decays as $log\mathrm{}\left(t\right)\mathrm{}$ when vibrations are introduced. We propose a simple model for this effect.

• Received 15 July 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.40