(Color online) Avalanche size distribution with open boundary conditions for (a) different the value of the parameter β with the system size N = 35². Different curves correspond to β = 0.40, 0.60, 0.80, 0.90, 0.95, and 1.0, from left to right. For comparison purposes, the original OFC model of α = 0.25 is shown in the direction of the arrow. (b) Distribution of earthquake size for the different system size with β = 1.0.