Mechanisms for Friction of Rock at Earthquake Slip Rates

Understanding dynamic friction through spontaneously evolving laboratory earthquakes

“…One weakening mechanisms with extensive theoretical and experimental support is flash heating2223738. According to the flash heating friction law, the friction coefficient evolves as:…”

Deeper penetration of large earthquakes on seismically quiescent faults

“…In laboratory settings, dynamic weakening processes have been ubiquitously reported in high-velocity rock friction experiments, attributed to a variety of mechanisms such as flash heating, thermal pressurization of pore-fluids, thermal decomposition, and silica gel lubrication (18,97, and references therein). Tanikawa and Shimamoto (98) show that the same rock samples taken from the Chelungpu fault zone can be velocitystrengthening -stable -at low slip rates and allow for dynamic weakening through thermal pressurization at high slip rates, supporting such combination of fault properties in the real world.…”

Is frictional heating needed to cause dramatic weakening of nanoparticle gouge during seismic slip? Insights from friction experiments with variable thermal evolutions

“…Yao et al [2016] questioned the effectiveness of powder lubrication based on the observation of high friction in sheared gouges with nanoparticles present but with limited temperature rise. By examining the dynamic fault-weakening mechanisms as summarized in Tullis [2015], we argue that the only remaining candidate mechanisms, which have to be thermal in origin or thermally enhanced, are flash heating and rapid superplastic deformation. The use of dry MgO nanopowder avoids the complexity arising from potential phase changes of minerals, comminution, thermochemical pressurization, and frictional melting.…”

“…Although dynamic weakening of faults is common, similar for all rock types [e.g., Di , the weakening mechanisms and their dominance depend on rock type as well as environmental parameters [Niemeijer et al, 2012;Tullis, 2015]. Although dynamic weakening of faults is common, similar for all rock types [e.g., Di , the weakening mechanisms and their dominance depend on rock type as well as environmental parameters [Niemeijer et al, 2012;Tullis, 2015].…”

“…Based on recent high-velocity rock friction studies, the term "powder lubrication" has been used to describe the fault weakening accompanying the formation of nanoparticles [Han et al, 2010Reches and Lockner, 2010], which is probably partly inspired by many tribological studies in material science [e.g., Rapoport et al, 2003;Wornyoh et al, 2007]. However, methodologically speaking, the effectiveness of an individual mechanism cannot be evaluated without controlling temperature conditions during highvelocity sliding, given that several weakening mechanisms may superpose and most of them are thermally activated [Niemeijer et al, 2012;Tullis, 2015]. However, methodologically speaking, the effectiveness of an individual mechanism cannot be evaluated without controlling temperature conditions during highvelocity sliding, given that several weakening mechanisms may superpose and most of them are thermally activated [Niemeijer et al, 2012;Tullis, 2015].…”