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Simulating the Formation and Evolution of Complex Fracture Patterns Arising From Shallow Strike-Slip Faulting With Finite and Discrete Element Analyses

Description: 

Shallow strike-slip faulting generates complex distributions of deformation that range from networks of

en-echelon fractures and contractional and extensional structures to through-going shear zones expressed

at Earth’s surface. Distributed inelastic deformation accommodated by these features affects the amount

of fault slip that reaches Earth’s surface, thereby biasing slip estimates used for probabilistic seismic

hazard and fault displacement hazard analyses. These well-documented fractures and shear structures

have been studied in laboratory, field, and numerical analyses, but field interpretations are typically

limited to 2D perspectives, and numerical investigations often cannot resolve discrete, localized shear

structures.

In this investigation, we use 3D finite element method (FEM) and 3D discrete element method (DEM)

models to examine how changes in shallow fault zone structure, material properties, and strike-slip

loading conditions affect the predicted distributions of fault slip and strain. We use the unique advantages

of FEM models (e.g., computational efficiency and straight-forward material parameterizations) and

DEM models (e.g., improved resolving power in capturing discrete shear-zone structure development and

evolution) to understand how material properties of the shallow crust, such as the internal angle of

friction, cohesion, and dilatancy, affect the shallow fault zone fracture patterns in strike-slip faulting

regimes. Our models suggest that DEM particle-packing densities and inferred material dilatancy strongly

influence the complexity of shallow shear zones, where branching shear structures that develop within

dilatant materials contrast with subvertical, planar structures that form in non-dilatant materials. In these

models, the evolution of material dilatancy with increasing fault slip also influences the expression of

fault zone deformation as fault slip continues to accrue. We compare our results with data-constrained

field sites to understand how these models may inform surface displacement and deformation distribution

predictions surrounding strike-slip faults.

Session: Characteristics and Mechanics of Fault Zone Rupture Processes, from Micro to Macro Scales - II

Type: Oral

Date: 5/2/2024

Presentation Time: 11:30 AM (local time)

Presenting Author: Curtis

Student Presenter: No

Invited Presentation: 

Authors