Some further analogies between the Bak-Sneppen model for biological evolution and the spring-block earthquake model

In recent years, a great deal of attention has been devoted to so-called self-organized critical (SOC) systems, which are open, extended systems that organize themselves into steady metastable states without any temporal- or spatial-predominant scale (except those imposed by the finite size of the system). The SOC concept has been used to describe the statistical properties of several physical systems through numerical models based on cellular automaton. In particular, Bak and Sneppen proposed a SOC model for biological evolution at the level of entire species or faunas that exhibit punctuated equilibrium behavior. On the other hand, Olami, Feder and Christensen suggested that a two-dimensional spring-block earthquake model can explain some properties of real seismicity. In this paper, we show that there exist several further interesting analogies between these SOC models, besides those remarked on by other authors. Both of them exhibit punctuated equilibrium in the long term, which leads us to suggest an equivalent characterization of seismic and "evolutionary" provinces through the long-term slopes of the stair-shaped graphs of cumulative activity in the course of time.