  A precursory dynamics, motivated by the analysis of recent experiments on
solid-on-solid friction, is introduced in a continuous cellular automaton that
mimics the essential physical contents of earthquake source processes. The
resulting system of equations for the inter-event cycle can be decoupled and
yields an analytical solution in the mean-field limit, exhibiting a smoothing
effect of the dynamics on the stress field. Simulation results show the
resulting departure from scaling at the large-event end of the frequency
distribution, and support claims that the field leakage may parametrize the
superposition of scaling and characteristic regimes observed in real earthquake
faults.
