A physical model for the precursory magnetic anomalies of the M5.4 Alum Rock and M6.0 Parkfield earthquakes

Here, we propose an alternative physical model, based on the concept of criticality, for the explanation of the observed magnetic signals prior to the M6.0 Parkfield and the M5.4 Alum Rock earthquakes. Motivated by an analogous experience from major earthquakes in Greece, where both magnetic field variations and seismic electric signals were also recorded few weeks before the main shock, we suggest that in all these cases, similar dynamic processes characterized by critical behaviour should govern the corresponding pre-focal areas when the relevant precursory signals emerged.