DYNAMICS OF SPRING-BLOCK MODELS - TUNING TO CRITICALITY

We have studied the homogeneous Burridge-Knopoff spring-block model wi th nonlinear friction introduced by Carlson and Langer [Phys. Rev. Let t. 62, 2632 (1989); Phys. Rev. A 40, 6470 (1989)]. There are several d ifferent velocity scales that define the model and divide the behavior of the system into distinct regimes. Over much of the parameter space defined by these velocities the system appears to be self-organized t o what is reminiscent of a first-order transition. As the friction non linearity is varied, there appears to be a continuous (critical) trans ition to a regime where a global event is continually occurring.