We consider a two-dimensional model for quasi-static evolution of four parallel faults. The model is based on the physics of continuum, with slips along the faults, long-range interactions, a distribution of barriers and asperities, a velocity dependent friction, healing and reactivation of cohesive forces, and a mutual causality between faulting and tectonic forces all taken into account. Both the long-term time series of seismic activity and details of seismic and aseismic crustal deformations during each phase of the earthquake cycle are produced by the model. It is shown that the system whose evolution is described by a set of deterministic differential equations may exhibit periodic or quite irregular (despite its assumed symmetry) behavior, depending on model parameters. ¿ American Geophysical Union 1995