The Impact of Fault Zone Plasticity on Sequences of Earthquakes and
Aseismic Slip: The Role of Stress Orientation and Bulk Cohesion
- Mohamed Abdelmeguid
, - Ahmed Elbanna

Mohamed Abdelmeguid

University of Illinois at Urbana Champaign, University of Illinois at Urbana Champaign
Corresponding Author:meguid@illinois.edu
Author ProfileAhmed Elbanna

University of Illinois at Urbana Champaign, University of Illinois at Urbana Champaign
Author ProfileAbstract
We present a coupled finite element spectral boundary integral framework
for modeling sequences of earthquakes and aseismic slip on a 2-D planar
rate-and-state fault with off-fault visco-plastic response in the plane
strain approximation. The model resolves both slow aseismic deformation
and inertia effects during rapid slip. We perform two sets of
simulations with different choices of cohesion. The first set implements
a relatively large value of the cohesion parameter, which results in
limiting inelastic strain accumulation to dynamic rupture phases. The
second set implements a smaller cohesion, allowing for plastic strain to
accumulate in both the seismic and aseismic phases of the earthquake
cycle. For the first model, our results indicate that the extent and
distribution of plastic strain depend on the angle of maximum
compressive principal stress. At larger angles, inelastic strain
accumulates on the extensional side of a dynamically propagating
rupture. At smaller angles, the extent of plasticity is limited to the
compressional side of the domain. At smaller cohesion values, off-fault
plasticity may occur during the aseismic phases of the earthquake cycle,
which alter the nucleation and earthquake sequence pattern. Furthermore,
our results at lower cohesion values indicate that plastic strain
accumulation may occur in both the extensional and compressional sides
of the off-fault bulk even at higher angles. This produces damage
patterns that deviate from the traditional off-fault fan-like
distribution observed in dynamic rupture simulations and emphasizes the
significance of long-term deformation in interpreting observations.