Exciting news! We're transitioning to the Statewide California Earthquake Center. Our new website is under construction, but we'll continue using this website for SCEC business in the meantime. We're also archiving the Southern Center site to preserve its rich history. A new and improved platform is coming soon!

SCEC2022 Plenary Talk, Fault and Rupture Mechanics (FARM)

Modeling co-evolution of slip and fault zones in a Sequence of Earthquakes and Aseismic Slip (SEAS) model with off-fault plasticity

Mohamed Abdelmeguid, Md Shumon Mia, & Ahmed E. Elbanna

Oral Presentation

2022 SCEC Annual Meeting, SCEC Contribution #12495
Geological and seismological observations of fault zones suggest the existence of a damaged core that has different properties from those of the surrounding host rock. However, modeling long term damage evolution within fault zones remains challenging numerically due to the conundrum of spatial and temporal scales that govern the physics. To address this computational challenge, we present a coupled finite element -spectral boundary integral equation framework for modeling SEAS on 2-D plane strain RSF faults embedded within a bulk with visco-plastic response. The exact domain truncation enabled by the spectral boundary integral formulation reduces the overall discretized volume, and conseque...ntly, reduces the computational cost and enable higher resolution. We use a rate-dependent pressure-sensitive non-associative Drucker-Prager plasticity model to approximate the inelastic response of the fault zone.
When considering a single fault, our results suggest that bulk plasticity plays an important role in the co-evolution of fault zones and seismicity with strong feedback on the local stress fields. Aseismic deformation and aseismic plastic strain accumulation evolve the stress field and bias plasticity accumulation during dynamic ruptures leading to damage patterns that deviate from the traditional off-fault fan-like distribution observed in single dynamic rupture simulations and emphasizes the significance of long-term deformation in interpreting observations. We tie our findings with field observations regarding the scaling of damage zone width with respect to distance from the fault and slip. Furthermore, we observe that weak fault zones, as parametrized by lower values of yield strength, may favor rupture segmentation and complex spatio-temporal seismicity, while stronger fault zones show reduced complexity and quasi periodic earthquake pattern. This underscores the critical role of the time-dependent partitioning of deformation between fault slip and bulk plasticity. Moreover, when incorporating increased geometrical complexity through a model of compressional fault step-over, as an example, we demonstrate that plastic strain accumulation in the overlapping region may enhance fault interaction resulting in additional seismic events. Our on-going work contributes to understanding the interaction between nearby faults with nonlinear off-fault bulk rheology and complement the development of next generation physics-based seismic hazard models.