SCEC Award Number 17220 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Can Fault Gouge Reduce Effects of Fault Roughness on Rupture Dynamics?
Investigator(s)
Name Organization
Shuo Ma San Diego State University
Other Participants 1 graduate student
SCEC Priorities 2d, 2e, 2c SCEC Groups Geology, CS, FARM
Report Due Date 06/15/2018 Date Report Submitted 11/12/2018
Project Abstract
 We consider a poro-elasto-plastic model of fault gouge and study its effects on the rupture dynamics of fractally rough faults. The model consists of a combined Mohr–Coulomb and end-cap yield surface in the gouge layer and allows compaction and dilatancy with undrained pore-pressure changes. We show that gouge compaction at restraining bends causes pore-pressure increase and allows rupture to propagate through segments that arrest rupture in the case with only the brittle failure off the fault. On the other hand, strengthening by undrained gouge dilatancy at releasing bends limits the tendency of supershear rupture from the case with only the brittle off-fault failure. Slip distributions and rupture velocities become more uniform due to the stabilizing tendency of the pore fluids in the fault gouge. The previously observed tendency for ruptures to accelerate and decelerate at releasing and restraining bends respectively can be reversed.
Intellectual Merit The undrained gouge plasticity can significantly affect rupture dynamics on rough faults. Current rough fault models only consider off-fault plasticity in the damage zone and found that rupture tends to accelerate at releasing bends and decelerate at restraining bends. However, we found that with undrained gouge plasticity these behaviors can be reversed and in general rupture dynamics is more stabilized and high-frequency radiation reduced. There is an urgent need in considering fault gouge plasticity in SCEC 5.
Broader Impacts This project helps to educate a graduate student in modeling earthquake rupture dynamics.
Exemplary Figure Figure 4