Earth Planets Space, Vol. 56 (No. 8), pp. 749-760, 2004
Frank Evison1 and David Rhoades2
1School of Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand
2Institute of Geological and Nuclear Sciences, P.O. Box 30-368, Lower Hutt, New Zealand
(Received December 11, 2003; Revised March 24, 2004; Accepted March 30, 2004)
The principles of self-organized criticality (SOC) provide a framework for understanding the process by which individual earthquakes are generated. The SOC principles of fractality, scaling, hierarchy, and extreme sensitivity to initial conditions, are exhibited by the precursory scale increase (Y) phenomenon, which we interpret as evidence of a long-term generation process. We have accordingly included SOC in a three-stage faulting model of seismogenesis. Fractality is represented by the Gutenberg-Richter relation, which is relied on for analysing the precursory scale increase (Y) phenomenon. Scaling characterizes the parameters of space, time and magnitude that relate the precursory seismicity to the mainshock and aftershocks. The validity of these relations is supported by application of the EEPAS model. Scaling also underlies the Mogi criteria, which are invoked to explain a selfgenerated transient effect, and hence the long duration of the seismogenic process. Hierarchy clarifies the otherwise complex situations that arise when two or more earthquakes are in process of generation at overlapping places and times. Extreme sensitivity to initial conditions explains why, with rare exceptions, both the seismogenic process and the culminating earthquake are initiated with no recognizable immediate trigger. The only exception so far observed for the seismogenic process is the proposed triggering, on 1992.06.28, of the long-term Hector Mine (California) process by the nearby Landers mainshock.
Key words: Seismogenesis, self-organized criticality, fractals, scaling, hierarchy.