Fracture mechanics determine the lengths of

interface ruptures that mediate frictional motion

Elsa Bayart, Ilya Svetlizky and Jay Fineberg*

 

The transition from static to sliding friction is mediated by

rapid interfacial ruptures1–5 propagating through the solid

contacts forming a frictional interface6. While propagating,

these ruptures correspond to true shear cracks7. Frictional

sliding is initiated only when a rupture traverses the entire

interface1; however, arrested ruptures can occur at applied

shears far below the transition to frictional motion8–17. Here

we show, by measuring the real contact area and strain

fields near rough frictional interfaces, that fracture mechanics

quantitatively describe rupture arrest and therefore determine

the onset of overall frictional sliding. Our measurements reveal

both the local dissipation and the global elastic energy released

by the rupture. The balance of these quantities entirely determines

rupture lengths, whether finite or system-wide. These

results confirm a fracture-mechanics-based paradigm7,15,18 for

describing frictional motion and shed light on the selection18–21

of an earthquake’s magnitude.