Rate and state dependent friction laws and the prediction of earthquakes: What can we learn from laboratory models?

Earthquakes can be considered to be a result of tribological instability in the system of faults of the Earth's crust. Similar instabilities can be reproduced and studied in detail in laboratory-scale experiments. In this work, the earthquake model under study is a tribosystem with pronounced stick-slip behavior. Measurement of the motion of the system with a resolution of 8 nm shows that slow creep is actually observed throughout the stick stage and it accelerates as the instability point is approached. This motion is regular enough to serve as a basis for the prediction of the onset of instability. It is shown that the motion of a solid, both at the stage of slow creep and at that of fast slip is well described by Dieterich's friction law, which takes the dependence of friction on sliding velocity and internal state variable into account, if we supplement it with the contribution of local contact compliance. In the immediate vicinity of the instability point, a universal behavior is observed, making highly accurate prediction of the onset of unstable slip from creep observations possible. We show that observation of the creep preceding a tribological instability makes both short term and long term predictions of the time until instable sliding in laboratory models possible. The problems of extending this approach to real distributed systems are discussed. (C) 2012 Elsevier B.V. All rights reserved.