Accelerated creep as a precursor of friction instability and earthquake prediction

Earthquakes can be considered as a result of tribological instability in a system of faults of the Earth 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 accelerated as the instability point is approached is actually observed throughout the stick stage. This motion is regular enough to serve as a basis for 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 the Dieterich friction law, which takes into account the dependence of friction on rate and internal state variable, if we supplement it with the contribution of local contact rigidity. In the immediate vicinity of the instability point a universal behavior is observed making possible highly accurate prediction of the onset of unstable slip from creep observations.