EARTHQUAKE MECHANISM AND PREDICTABILITY SHOWN BY A LABORATORY FAULT

Slip events generated in a laboratory fault model consisting of a circ ulinear chain of eight spring-connected blocks of approximately equal weight elastically driven to slide on a frictional surface are studied . It is found that most of the input strain energy is released by a re latively few large events, which are approximately time predictable. A large event tends to roughen stress distribution along the fault, whe reas the subsequent smaller events tend to smooth the stress distribut ion and prepare a condition of simultaneous criticality for the occurr ence of the next large event. The frequency-size distribution resemble s the Gutenberg-Richter relation for earthquakes, except for a falloff for the largest events due to the finite energy-storage capacity of t he fault system. Slip distributions, in different events are commonly dissimilar. Stress drop, slip velocity, and rupture velocity all tend to increase with event size. Rupture-initiation locations are usually not close to the maximum-slip locations.