MODEL OF EARTHQUAKE RECURRENCE - ROLE OF ELASTIC-WAVE RADIATION, RELAXATION OF FRICTION, AND INHOMOGENEITY

We have constructed a dynamical model of seismicity, wherein a fault is embedded in an infinite, continuous, elastic medium. Therefore the influence of the energy dissipated in seismic wave radiation on the sequential history of model earthquakes is fully taken into account. In this model, the drop in friction at rupture takes place gradually, thus introducing a relaxation dimension. As an example, we consider a finite homogeneous fault that is terminated by infinitely strong barriers at the ends. The features of the seismicity are dominated by the stresses that are reflected from the unbreakable barriers. There is a strong dependence of the patterns of seismicity on the ratio of the relaxation dimension to the distance between the barriers at the ends. For large values of this parameter, We find that periodicity begins after a short transient interval and a dominance of the statistical distributions by large events that break completely through the fault from end to end. For small values of this parameter, smaller-scale seismicity is interspersed with the large events, and no periodicity is observed within the time spanned by the computations. We conclude that major unquenched heterogeneities, such as those found at barriers, which we suppose arise in nature due to the nonuniform geometry of faults, are vital ingredients for generating complex seismic histories as well as giving rise to the complex features of individual earthquake source-time functions in models of seismicity as a dynamical process.