Model for intermediate‐term precursory clustering of earthquakes

Abstract

A causal sequence of an earthquake swarm, extended quiescence, foreshocks, and main shock can be understood in terms of an aggregation model of crack growth and ultimate fusion on a multiplanar earthquake fault system. The rheological model is one of accelerated crack growth under conditions of slip weakening, coupled with a slow recovery of static friction after fracture. Once a slip feature has been generated that spans a large part of the available geometry, a stress shadow is cast on other, neighboring cracks that strongly retards and inhibits crack growth, thus initiating the quiescent phase abruptly. The success of the model depends on the assumption that nonlinear rheology regulates the rate of slip and that earthquake faults are not simply connected surfaces but instead have many strands.