Friction and Fracture: Geophysics in the lab

What happens at the interface between two solid bodies in contact when they start sliding? This problem has important implications to various fields such as engineering, where the challenge is to control friction, or earthquake dynamics, where prediction of earthquakes occurrence and magnitude is crucial. A frictional interface is composed of an ensemble of discrete contacts that resist to shear. Sliding motion is mediated by the propagation of an interfacial rupture, breaking the micro-contacts, as revealed by measurements of the real contact area and stress fields near the interface. In this talk, we will show that these ruptures are true shear cracks as they propagate and as they stop. We study the rupture dynamics along heterogeneous interfaces, i.e. in presence of a 3rd body - lubricant or granular matter. The impact of these results on earthquakes dynamics will be discussed.