Off-fault plasticity controls the spectrum of fault slip: from slow to fast and from small to large

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

Published September 11, 2022, SCEC Contribution #12128, 2022 SCEC Annual Meeting Poster #135

Earthquakes are among nature’s deadliest and costliest hazards. Physics-based simulations are essential to complement the lack of data and elucidating the complex patterns of earthquakes. While significant progress has been made in understanding earthquake source processes in linear elastic domains, the response of the rocks near the fault is complex and likely to be inelastic due to the extreme stresses and deformations associated with fault slip. The effect of this more realistic fault zone response on seismic and aseismic fault slip is poorly understood. Here, using a hybrid finite element-spectral boundary integral scheme (FEBE), we simulate sequence of earthquakes and aseismic slip of a rate-and-state fault embedded in an elastoplastic bulk subject to slow tectonic loading. We show that off-fault plasticity significantly influences the source characteristics. Specifically, off-fault plasticity may lead to partial ruptures and emergence of spatial segmentation as well as temporal seismic clustering. Seismicity pattern changes from simple periodic to complex depending on the bulk yield strength and viscosity. We also observe small repeating earthquakes and slow slip for lower yield strength. When yield strength is further reduced, the fault remains locked and off-fault plastic deformation compensates for the slip deficit. Simulating a simple spring-slider model, we observe analogous features of different sliding pattern ranging stick-slip, slow slip, and locked depending on the stiffness and yield strength of the spring. These results highlight the implications of plasticity on frictional sliding and indicate the importance of characterizing the fault zone mechanical response beyond their elastic properties to better inform seismic hazard models.

Citation
Mia, M., Abdelmeguid, M., & Elbanna, A. E. (2022, 09). Off-fault plasticity controls the spectrum of fault slip: from slow to fast and from small to large. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)