The contact between macroscopic rough solids is made of many micrometric asperities in contact. Under increasing shear force, a catastrophic rupture of the interface can occur through the propagation of a micro-slip front at speeds close to that of sound in the material [1]. Gross sliding of the solids only begins when the front has spanned the whole interface.

I will first introduce a multi-scale model capable of reproducing the space and time features of micro-slip fronts observed in recent experiments, in particular the existence of anomalously slow fronts [2]. I will then identify slow slip as a sufficient physical mechanism for slow fronts to occur. Whether slow fronts are actually observed is controlled both by the interfacial stresses and by a state parameter related to the width of the local distribution of forces among micro-junctions.

[1] S.M. Rubinstein et al., Nature (2004) ; O. Ben-David et al., Science (2010)

[2] J.K. Trømborg et al., PNAS 111, 8764 (2014)