Spatiotemporal evolution of seismic and aseismic frictional sliding with bulk plasticity

Natural fault zones exhibit multiscale geometric and rheological complexity. They also show a wide range of seismicity patterns including slow slip, tremors. and large earthquakes. It is critical to understand the dynamics of these different events as they impact the structural reliability of the infrastructure and subsurface geo-energy activities. Traditionally, conditions governing the stability of frictional sliding and resulting seismicity patterns are often attributed to the on-fault frictional properties with idealized off-fault elastic response. However, fault slip may lead to the inelastic deformation in the bulk which in turn may influence the resulting slip patterns. Physics-based simulations of Sequences of Earthquakes and Aseismic Slip (SEAS) are essential to complement the lack of sufficient observational data, and to understand the complex patterns and source processes of earthquakes. This study focuses on simulating SEAS for complex fault zones incorporating off-fault plasticity. We simulate SEAS for different fault zone configurations including single fault, fault stepovers and fault networks. We also simulate injection induced SEAS with evolving pore pressure for different scenarios including single and multiple faults. We use rate-and-state friction to model the fault interfacial response and Dracker-Prager plasticity model to simulate the bulk inelastic material response. We employ a hybrid numerical framework, FEBE, that combines the finite element method (FEM) and the spectral boundary integral method (SBIM), and alternates between quasi-dynamics and dynamics solver. The hybrid scheme allows high resolution FEM discretization of the nonlinear fault zone and truncation of the remaining homogeneous elastic half spaces through SBIM. Alternating algorithms of quasi-dynamics and dynamics solvers capture full inertia effect during fast coseismic rupture and approximate the inertia through radiation damping during inter-seismic slow deformation. The simulation results for SEAS with off-fault plasticity show that interaction of fault slip and off-fault plasticity leads to rupture arrest and spatiotemporal clustering of seismicity. We also find emergence of a spectrum of slip patterns including locked fault, slow slip, and partial ruptures depending on bulk yield strength relative to fault frictional strength. For fault stepovers, we simulated SEAS for different configurations including tensile stepover and compressive stepover. Tensile stepover with off-fault plasticity shows more complex seismicity patterns including rupture segmentation and frequent rupture jumping from one fault to another. Evolution of off-fault plasticity depends on stepover gap, overlap, underlap, and whether the stepover is tensile or compressive. We also simulate a fault network that includes a primary fault and secondary faults with various orientations to represent a complex damage zone. We observe that the activation of these secondary faults may alter the seismicity pattern, leading initially to segmented ruptures that potentially evolve to a mature state with full fault-spanning events on the primary fault. The time it takes for a fault network to mature varies based on the secondary faults' frictional strength and size. Further considering fluid effects in these simulations, by incorporation of pore pressure perturbations due to fluid injection, we note both spatially distributed and temporally clustered induced seismic events that emulate real observations. These results contribute to understand the seismic source processes for complex fault zone and shed light on the coevolution of fault zone and seismicity. It may help in developing efficient seismic hazard models for improved societal preparedness.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Mia, Md Shumon

Contributors dc:contributor

• Elbanna, Ahmed
• Matlack, Kathryn
• Duarte, Armando
• Cattania, Camilla

• Friction
• Plasticity
• Earthquake Cycle
• Seismic Wave Propagation
• Finite Element Method
• Spectral Boundary Integral

Statement dc:rights

• Copyright 2024 Md Shumon Mia

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/124311

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F124311