Finite element simulations of dynamic shear rupture experiments and dynamic path selection along kinked and branched faults

Abstract

[1] We analyze the nucleation and propagation of shear cracks along nonplanar, kinked, and branched fault paths corresponding to the configurations used in recent laboratory fracture studies by Rosakis (2003, 2009). The aim is to reproduce numerically those shear rupture experiments and from that provide an insight into processes which are active when a crack, initially propagating in mode II along a straight path, interacts with a bend in the fault or a branching junction. The experiments involved impact loading of thin Homalite-100 (a photoelastic polymer) plates, which had been cut along bent or branched paths and weakly glued back together everywhere except along a starter notch near the impact site. Strain gage recordings and high-speed photography of isochromatic lines provided characterization of the transient deformation fields associated with the impact and fracture propagation. We found that dynamic explicit 2-D plane-stress finite element analyses with a simple linear slip-weakening description of cohesive and frictional strength of the bonded interfaces can reproduce the qualitative rupture behavior past the bend and branch junctions in most cases and reproduce the principal features revealed by the photographs of dynamic isochromatic line patterns. The presence of a kink or branch can cause an abrupt change in rupture propagation velocity. Additionally, the finite element results allow comparison between total slip accumulated along the main and inclined fault segments. We found that slip along inclined faults can be substantially less than slip along the main fault, and the amount depends on the branch angle and kink or branch configuration.

Analogue earthquakes and seismic cycles: experimental modelling across timescales

“…Rousseau and Rosakis (2009) investigated the effect of more complex fault geometries including kinking and branching on rupture propagation in a homalite material. At the same time, Templeton et al (2009) were able to simulate experimental results numerically. The control on rupture velocity in general and super-shear ruptures specifically is a very active field in analogue earthquake studies (e.g Lu et al, 2009;Schubnel et al, 2011;Mello et al, 2010Mello et al, , 2014Mello et al, , 2016Passelègue et al, 2013Passelègue et al, , 2016.…”

Stress concentration near stiff inclusions: Validation of rigid inclusion model and boundary layers by means of photoelasticity

“…Experimental stress analysis near a crack or a void has been the subject of an intense research effort (see for instance Lim and Ravi-Chandar [19,20], Schubnel et al [25], Templeton et al [27]), but the stress field near a rigid inclusion embedded in an elastic matrix, a fundamental problem in the design of composites, has surprisingly been left almost unexplored (Theocaris [28]; Theocaris and Paipetis [29,30], Reedy and Guess [22]) and has never been investigated via photoelasticity. 1 Though the analytical determination of elastic fields around inclusions is a problem in principle solvable with existing methodologies (Movchan and Movchan [14], Muskhelishvili [15], Savin [24]) detailed treatments are not available and http://dx.doi.org/10.1016/j.engfracmech.2014.03.004 0013-7944/Ó 2014 Elsevier Ltd. All rights reserved.…”

Finite Element Modeling of Branched Ruptures Including Off-Fault Plasticity

“…This formulation does not take important dynamic weakening effects into account, but has successfully been used to model earthquake rupture in single fault models (e.g., Duan and Oglesby, 2005), fault step models (e.g. Harris and Day, 1999) and branched geometries (e.g., Aochi et al, 2000;Kame et al, 2003;Templeton et al, 2009).…”