STICK-SLIP DYNAMICS IN THE RELAXATION OF STRESSES IN A CONTINUOUS ELASTIC MEDIUM

We report on experimental results on the dynamical behavior of the stress relaxation in a model system for earthquakelike dynamics. In the experiments, a continuous elastic medium, namely, a transparent gel, is sheared at a very slow rate in between two coaxial circular cylinders. The stress relaxations are investigated locally by means of photoelastic techniques. We find four different stick-slip dynamical regimes. Three of them are reminiscent of the unstable solutions of the Burridge-Knopoff model: the sliding, the global relaxation, and the solitonlike propagating solutions. The fourth regime shows complex spatiotemporal behavior involving events of all sizes. For this last type of behavior the statistics of event duration, event separation, and amplitude show exponential behavior.