SCEC Award Number 09090 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Inelastic Off-Fault Deformation During Repeated Earthquake Ruptures and Plastic Zone Scaling
Name Organization
Renata Dmowska Harvard University James R. Rice Harvard University
Other Participants Templeton, Elizabeth L. (graduate student research assistant)
SCEC Priorities A7, A8, A9 SCEC Groups FARM, WGCEP, WGCEP
Report Due Date 02/28/2010 Date Report Submitted N/A
Project Abstract
We addressed how inelastic deformation in off-fault damage zones interacts with earthquake rupture. A major focus was on the way that plasticity interacts with other features in determining a possibly preferred directivity of propagation along faults separating seismically dissimilar materials. Also, we examined residual stress fields left as a result of plastic deformation in a single rupture, and showed in a simple case how those residual stresses would make the next rupture propagate with different speed, and leave a generally lesser increment of plastic strain in its wake. Finally, we showed that while a band of plastically deformed material was left along the border of a propagating rupture, only a very thin sliver of that plastic region, located near the rupture front and having a geometrically complex relation to the slip-weakening zone, was deforming plastically at any given moment in time.
Intellectual Merit The project has provided a rigorous formulation, for ruptures along faults separating seismically dissimilar materials, of the relations among preferred rupture directivity, orientation of the regional stress field relative to the fault, and presence of plastic-yielding damage zones preferentially on one or the other side of the fault. Also, it poses a problem of explaining the remarkable geometric features of the momentarily active zones of plastic straining (see the final Figure).
Broader Impacts The activity on this project has been a major part of the Ph.D. thesis research of Elizabeth Templeton, and has contributed to that of Nora DeDontney and Robert Viesca.
Exemplary Figure Fig. 2. Changes in rupture propagation and plastic deformation result from changing Psi (angle which max principal compressive stress makeswith rupture plane). (a) Contours of plastic deformation. (Note: there is a 2x vertical exaggeration for easier viewing of the plastic zone, but which makes the Psi angle appear larger than actual.) (b) Slip velocity at different times during rupture. (c) Rupture velocity to the right and left of the nucleation. This shows how the presence of plastic yielding together with low angles Psi of the principal compression direction relative to the fault can reverse the elastically predicted preferred direction of propagation. (DeDontney et al., JGR, 2011)