Self-organized criticality in an isotropically driven model approaching equilibrium

Self-organized criticality (SOC) in systems governed by stick-slip dynamics is studied by means of a spring-block model. Contrary to conventional models which are loaded additively in their stationary states, our model is driven towards equilibrium in a multiplicative and isotropic manner via a temporally increasing coupling strength. A coarsening process builds up correlations in the bulk and establishes power-law avalanche size distributions, independent of boundary conditions and system parameters. The observed behavior is robust and suggests that some experimental systems approaching equilibrium via a punctuated threshold dynamics may well show SOC.