SCEC Award Number 11126 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title The Effect of Off-Fault Damage on the Propagation of an Earthquake Rupture
Investigator(s)
Name Organization
Harsha Bhat University of Southern California Charles Sammis University of Southern California
Other Participants
SCEC Priorities A7, A9, B2 SCEC Groups FARM, Seismology, Geology
Report Due Date 02/29/2012 Date Report Submitted N/A
Project Abstract
 The objective of this work was to develop a micro-mechanically motivated constitutive law for a brittle elastic material that also properly accounted for micro crack growth at high loading rates. Earthquake ruptures tend to create a lot of off-fault fracture damage. The main question we were after was how this damage zone was created in the first place and the role it plays in the dynamics of earthquake rupture. We showed that the constitutive model developed, as part of the proposal, matched experimental data for brittle rock materials extremely well. We then implemented this constitutive model in a numerical earthquake rupture calculation and showed that off-fault damage can introduce asymmetry in rupture propagation. Also some times this damage tends to get localized which might be considered as the origin of a new fault segment.
Intellectual Merit This project aims at developing realistic constitutive models that properly accounts for off-fault damage. These constitutive models can be effectively implemented in earthquake rupture codes (as shown in one of the examples in the report). We are now in a position to ask questions about the spatial extent of damage zones and the role it plays in earthquake rupture dynamics. One might also be able to speculate, a bit more realistically, the question of overall evolution of fault zones itself.
Broader Impacts The model developed in this project are now being used by two graduate students (one in Ecole Normal Superiere, France and one at Caltech). Both students were not trained in earth sciences and are now motivated to pursue careers in that field (one student is applying as a graduate student this year in earth sciences).
Exemplary Figure Figure 1: Snapshot of a bilateral rupture propagating on the boundary between damaged and undamaged rock. Note the generation of dynamic damage in the tensile lobe of the right rupture tip. Rupture tips are denoted by the inverted triangles. [from Bhat et al, 2012 Journal of Applied Mechanics]