Slow slip and the transition from fast to slow fronts in the rupture of frictional interfaces

Abstract

The failure of the population of microjunctions forming the frictional interface between two solids is central to fields ranging from biomechanics to seismology. This failure is mediated by the propagation along the interface of various types of rupture fronts, covering a wide range of velocities. Among them are the so-called slow fronts, which are recently discovered fronts much slower than the materials' sound speeds. Despite intense modeling activity, the mechanisms underlying slow fronts remain elusive. Here, we introduce a multiscale model capable of reproducing both the transition from fast to slow fronts in a single rupture event and the short-time slip dynamics observed in recent experiments. We identify slow slip immediately following the arrest of a fast front as a phenomenon sufficient for the front to propagate further at a much slower pace. Whether slow fronts are actually observed is controlled both by the interfacial stresses and by the width of the local distribution of forces among microjunctions. Our results show that slow fronts are qualitatively different from faster fronts. Because the transition from fast to slow fronts is potentially as generic as slow slip, we anticipate that it might occur in the wide range of systems in which slow slip has been reported, including seismic faults.friction | multiscale modeling | onset of sliding | stick-slip T he rupture of frictional interfaces is a central mechanism in many processes, including snow slab avalanches, human object grasping, and earthquake dynamics (1). Rupture occurs through the propagation of a crack-like microslip front-the rupture frontacross the interface. This front represents the moving boundary between a stick region and a slipping region that coexist within the interface plane. In so-called partial-slip situations, fronts propagate quasistatically at a pace controlled by the external loading, as studied in mechanical engineering for decades (2, 3). Recently, fast cameras enabled the observation of much faster fronts, which are classified into three types: supershear fronts faster than the material's shear wave speed c s , sub-Rayleigh fronts propagating at velocities close to c s , and slow fronts much slower than c s (4-8). Whereas the first two types have been predicted theoretically, the physical mechanisms underlying slow fronts are still debated.A better understanding of slow fronts appears as a significant step toward an improved assessment of how frictional motion begins. It is also expected to shed light on the important topic of slow earthquakes, which have been increasingly reported in the last decade (1). In this context, an intense theoretical and numerical activity arose to investigate the origins and properties of rupture fronts. Two different approaches have been explored.On the one hand, 2D or 3D elastodynamic models have been used to relate the macroscopic loading conditions to the stress field along the contact interface (9-13). These local stresses were indeed shown experimentally to play a role in the selectio...

Minimal model for slow, sub-Rayleigh, supershear, and unsteady rupture propagation along homogeneously loaded frictional interfaces

“…Intermittent rupture then continues as long as the slow slip endures. A similar mechanism was found to control the transition from fast to slow rupture in a multi-asperity model [26], reproducing observations in laboratory experiments [4]. We also speculate that the start-stop regime found in this study may be an analog to observed periodic pulsing of aseismic events have been observed [16].…”

“…The range of observed front types have already been successfully reproduced by a variety of models. Arrested cracks have been reproduced using quasi-static models [18][19][20][21], or elastodynamic models in 1D [22,23] or 2D [24][25][26][27][28], assuming either continuous [19,[22][23][24][25]27] or discrete-microcontact-based friction laws [26,28], or fracture concepts [18,21]. Slip pulses have been reproduced using discrete [29] or continuum models assuming either a Coulomb [30], regularized Coulomb [31][32][33] or state-andrate [34,35] friction laws.…”

How collective asperity detachments nucleate slip at frictional interfaces

“…The different measures, from top to bottom, are defined in Eqs. (47)(48)(49). Note that (D.2) is identical to Fig.…”

Onset of Sliding of Elastomer Multicontacts: Failure of a Model of Independent Asperities to Match Experiments

“…Such improved models may incorporate those tangential interactions in ways similar to models already developed for the normal interactions during normal loading of rough surfaces (see e.g. [3,25,26,7,8]).…”