Damage spreading in a rice pile model

In a recent experiment with rice piles [V. Frette et al., Nature 379 (1996) 49] it was observed that the distribution of avalanches presents a power-law behavior for elongated rice, while avalanches for round rice present a characteristic length. These experiments showed that granular piles may display Self-Organized Criticality (SOC), but the behavior is not universal. We have recently presented a model for granular flow in a one-dimensional rice pile [P.M. Gleiser et al., Phys. Rev. E, in press] which exhibits the crossover from power law to stretched exponential behavior observed experimentally in the granular dynamics of rice piles. In this work, we use the damage spreading technique to study how a small perturbation (or damage) propagates through the system.