Finite element simulations of dynamic shear rupture experiments and dynamic path selection along kinked and branched faults
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 Rousseau and 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.
©2009. American Geophysical Union. Received 27 October 2008; accepted 13 May 2009; published 13 August 2009. All authors except A.J.R. and C.-E.R. were supported at Harvard by NSF-EAR grants 0440145 and/or 0809610 and by the Southern California Earthquake Center, which is funded by cooperative agreements NSF-EAR 0106924 and USGS 02HQAG0008 (this is SCEC contribution 1229). A.J.R. and C.-E.R. were supported by U.S. DOE grant DE-FG52-06NA26209, NSF-EAR grant EAR-0711545, and ONR MURI grant N0014-06-1-0730.
Published - Templeton2009p5780J_Geophys_Res-Sol_Ea.pdf