Complex dynamics in a one--block model for earthquakes

A two-dimensional earthquake model that consists of a single block resting upon a slowly moving rough surface and connected by two springs to rigid supports is studied. Depending on the elastic anisotropy and the friction force three generic regimes are possible: i) pure creep; ii) pure stick-slip motion; and iii) a mixed regime. In all cases the long-time dynamics (fixed point, periodic orbit or chaos) is determined by the direction of the pulling velocity. The possible relevance of our findings to real faults is briefly discussed.