Phase transitions in a spring-block model of earthquakes

We investigate the nature of the phase transitions that occur in one version of the Burridge-Knopoff spring-block model, which has been used to simulate tectonic motion along a fault. We find that by adjusting the parameters of the model, a variety of qualitatively different behaviors can be observed. As we vary one of the parameters, the system goes from a region where all the blocks are continuously moving to a region where the motion occurs in short, but violent, ruptures. We investigate the properties of the dynamics in these two regimes and the nature of the transition that occurs when the system is tuned from one regime into the other.