TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 56 (No. 8), pp. 773-793, 2004

Earthquake cycles and physical modeling of the process leading up to a large earthquake

Mitiyasu Ohnaka

The University of Tokyo, and University College London

(Received November 30, 2003; Revised June 15, 2004; Accepted July 1, 2004)

Abstract: A thorough discussion is made on what the rational constitutive law for earthquake ruptures ought to be from the standpoint of the physics of rock friction and fracture on the basis of solid facts observed in the laboratory. From this standpoint, it is concluded that the constitutive law should be a slip-dependent law with parameters that may depend on slip rate or time. With the long-term goal of establishing a rational methodology of forecasting large earthquakes, the entire process of one cycle for a typical, large earthquake is modeled, and a comprehensive scenario that unifies individual models for intermediate- and short-term (immediate) forecasts is presented within the framework based on the slip-dependent constitutive law and the earthquake cycle model. The earthquake cycle includes the phase of accumulation of elastic strain energy with tectonic loading (phase II), and the phase of rupture nucleation at the critical stage where an adequate amount of the elastic strain energy has been stored (phase III). Phase II plays a critical role in physical modeling of intermediate-term forecasting, and phase III in physical modeling of short-term (immediate) forecasting. The seismogenic layer and individual faults therein are inhomogeneous, and some of the physical quantities inherent in earthquake ruptures exhibit scale-dependence. It is therefore critically important to incorporate the properties of inhomogeneity and physical scaling, in order to construct realistic, unified scenarios with predictive capability. The scenario presented may be significant and useful as a necessary first step for establishing the methodology for forecasting large earthquakes.
Key words: Rational constitutive law, earthquake rupture, physics of rock friction and fracture, inhomogeniety, physical scaling, physical modeling, a unified scenario for earthquake forecasting.

Corresponding author E-mail: ohnaka@g05.itscom.net

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