Stability and localization of rapid shear in fluid‐saturated fault gouge: 2. Localized zone width and strength evolution

Abstract

Field and laboratory observations indicate that at seismic slip rates most shearing is confined to a very narrow zone, just a few tens to hundreds of microns wide, and sometimes as small as a few microns. Rice et al. (2014) analyzed the stability of uniform shear in a fluid‐saturated gouge material. They considered two distinct mechanisms to limit localization to a finite thickness zone, rate‐strengthening friction, and dilatancy. In this paper we use numerical simulations to extend beyond the linearized perturbation context in Rice et al. (2014), and study the behavior after the loss of stability. Neglecting dilatancy we find that straining localizes to a width that is almost independent of the gouge layer width, suggesting that the localized zone width is set by the physical properties of the gouge material. Choosing parameters thought to be representative of a crustal depth of 7 km, this predicts that deformation should be confined to a zone between 4 and 44 μm wide. Next, considering dilatancy alone we again find a localized zone thickness that is independent of gouge layer thickness. For dilatancy alone we predict localized zone thicknesses between 1 and 2 μm wide for a depth of 7 km. Finally, we study the impact of localization on the shear strength and temperature evolution of the gouge material. Strain rate localization focuses frictional heating into a narrower zone, leading to a much faster temperature rise than that predicted when localization is not accounted for. Since the dynamic weakening mechanism considered here is thermally driven, this leads to accelerated dynamic weakening.

The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain localization in 3D continua with application to seismic faults. Part II: Numerical implementation and post-bifurcation analysis

“…Platt et al (2014)). This a convenient proxy not only 255 for the evaluation of the shear band thickness, as explained below, but also for comparing numerical results with experimental ones that are obtained by Digital…”

Modeling of combined slip and finite sliding at spherical grain contacts

“…(26,27), the angles α T and α N depend only on the friction angle φ and initial position cos α u = y 0 /R, and are independent of the contact stiffness. This condition is very important for the experimental testing, i.e., when the values of relative position y 0 /R and angles α T (or α N ) are measured, the experimental friction coefficient can be established from the formulae (26,27). Moreover, T * max and N * max are also important for selecting the loading ring capacity in developing the inter-particle friction apparatuses.…”

“…The results of numerical solution of Eqs. (26,27) are shown in Fig. 4b, for the rightward motion of upper sphere of different radii and initial overlap of h 0 = 0.1 R 2 (R 1 = 1 m).…”

“…The induced contact instability along rock fault plane due to highly localized slip by such thermally driven weakening mechanism has recently been analyzed by Rice [26] and Platt et al [27]. Also an attempt was made by Ciavarella [28] to extend Mindlin's solution by introducing Griffith's fracture model for the inception of slip regime.…”

Frictional heating lubrication for submarine landslide

“…The calculated results for the thickness of shear zone often vary with models (e.g., Platt et al 2014;Chen and Rempel 2015). To date, it is still an open issue to predict the thickness of the basal shear zone in landslides because there are so many factors involved to affect the evolution of this shear zone.…”