Precursory Seismic Activation and Critical-point Phenomena

In this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability. We illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion. We draw an analogy between the steam explosion and a characteristic earthquake, and show that the power-law activation associated with the spinodal instability is essentially identical to the power-law increase in Benioff strain observed prior to characteristic earthquakes. We find that theory and actual data give very similar results.