Rupture Dynamics of Heterogeneous Frictional Interfaces

International audienceThe onset of sliding motion is conditional on the propagation of rupture fronts that detach the contacting asperities forming a frictional interface. These ruptures, when propagating over a fault surface, are the most common mechanism for an earthquake. Experimentally, the transition from static to sliding friction takes place when a rupture traverses the entire interface. But ruptures can also arrest before reaching the end of the interface. The determination of the mechanisms responsible for rupture arrest is of particular interest for understanding an earthquake's magnitude selection. Propagating ruptures have been shown to be true shear cracks, driven by singular fields at their tip, and fracture mechanics have been successfully used to describe rupture arrest along homogeneous frictional interfaces. Performing high temporal resolution measurements of the real contact area and strain fields, we demonstrate that the same framework provides an excellent quantitative description of rupture arrest along interfaces with heterogeneous fracture properties and complex stress distributions at a macroscopic scale. This work unravels the different mechanisms responsible for rupture arrest along model laboratory faults. This fracture-based paradigm opens a window to a wide range of possible consequences for frictional behavior along any two contacting bodies; from the centimeter scale to the scale of natural faults. Plain Language Summary An earthquake is a rupture front propagating along a fault, which breaks the solid contacts formed between the two fault faces. Ruptures are often arrested before spanning the entire length of the fault. Rupture lengths relate to earthquake magnitudes; the longer the rupture, the higher the magnitude. The aim of this study is to understand what causes rupture arrest, hence, what selects an earthquake's size. We mimic a fault in the lab by pressing and shearing two solid blocks until sliding motion initiates. We demonstrate that an arrest criterion derived from fracture mechanics theory is valid to determine if and where a rupture will arrest. Our conclusion is that rupture arrest occurs because of either value of the applied stress, when properly weighted, or a localized increase of the fracture energy, that is, the energy dissipated during the rupture propagation, along the interface

Rupture speed dependence on initial stress profiles: Insights from glacier and laboratory stick-slip

© 2014 The Authors. Slow slip events are now well-established in fault and glacier systems, though the processes controlling slow rupture remain poorly understood. The Whillans Ice Plain provides a window into these processes through bi-daily stick-slip seismic events that displace an ice mass over 100 km long with a variety of rupture speeds observed at a single location. We compare the glacier events with laboratory experiments that have analogous loading conditions. Both systems exhibit average rupture velocities that increase systematically with the pre-rupture stresses, with local rupture velocities exhibiting large variability that correlates well with local interfacial stresses. The slip events in both cases are not time-predictable, but clearly slip-predictable. Local pre-stress may control rupture behavior in a range of frictional failure events, including earthquakes

Rupture speed dependence on initial stress profiles: Insights from glacier and laboratory stick-slip

AbstractSlow slip events are now well-established in fault and glacier systems, though the processes controlling slow rupture remain poorly understood. The Whillans Ice Plain provides a window into these processes through bi-daily stick-slip seismic events that displace an ice mass over 100 km long with a variety of rupture speeds observed at a single location. We compare the glacier events with laboratory experiments that have analogous loading conditions. Both systems exhibit average rupture velocities that increase systematically with the pre-rupture stresses, with local rupture velocities exhibiting large variability that correlates well with local interfacial stresses. The slip events in both cases are not time-predictable, but clearly slip-predictable. Local pre-stress may control rupture behavior in a range of frictional failure events, including earthquakes