Predicting the propagation and interaction of frontal accretionary thrust faults with work optimization

McBeck, Jessica; Cooke, Michele L.; Fattaruso, Laura

doi:10.1016/j.tecto.2020.228461

Cited by 6 publications

(6 citation statements)

References 34 publications

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“…(2017) found that after the first pop‐up structure forms ahead of the main wedge, the formation of new forward‐vergent thrusts optimizes energy more than the formation of a backward‐vergent thrust in conjugate thrust pairs. A similar analysis in McBeck, Cooke, and Fattaruso (2020) showed that the backward‐vergent thrust generally forms before the forward‐vergent pair as occurs in Mechanism 2 in our simulations because of the higher shear stress and failure potential near the top of the sandpack at the backthrust nucleation point, relative to other areas of the wedge. The surface slope inflection from the adjacent and partially overlying sand wedge (or thrust sheet) was responsible for generating this zone of higher stress concentration.…”

Section: Discussionsupporting

confidence: 80%

Strain Localization Patterns and Thrust Propagation in 3‐D Discrete Element Method (DEM) Models of Accretionary Wedges

et al. 2023

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High‐resolution three‐dimensional discrete element method (DEM) simulations of sandbox‐scale models of accretionary wedges suggest thrusts follow a variety of propagation processes and orientations depending on a number of factors. These include the stage of development of the wedge (precritical vs. critical), basal friction, and type of thrust (forward vs. backward‐vergent). In terms of propagation processes, two clear mechanisms are identified. The first involves propagation from the décollement to the wedge top, similar to the standard model of thrust propagation seen in many kinematic models, and in the second, thrusts grow downward from an initial nucleation point just below the top surface of the wedge as well as upward from the décollement joining in the middle. In terms of orientation, forward‐vergent thrusts initially form at Roscoe (θR = 45° − Ψ/2) or Arthur orientations (θA = 45° − (ϕ + Ψ)/4), and over greater shortening, rotate into Coulomb orientations (θC = 45° − ϕ/2). To arrive at these results, a wide array of continuum parameters and fields were extracted from the DEM simulations, including stress, strain, strain rate, kinetic energy, Mohr‐Coulomb parameters, and proximity to yielding using the Drucker‐Prager criterion to visualize thrust nucleation and propagation. Lastly, the advantages and disadvantages of these continuum proxies for discerning failure in the granular assembly are considered, and the spatial and temporal relationship between proximity to yielding and strain localization (both pre‐peak and subsequent persistent shear banding) in the granular model of an accretionary wedge is explored.

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Section: Discussionsupporting

confidence: 80%

Strain Localization Patterns and Thrust Propagation in 3‐D Discrete Element Method (DEM) Models of Accretionary Wedges

et al. 2023

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“…Previous analyses have used some of these metrics to predict the direction of fracture growth from a preexisting fracture tip (e.g., Olson and Cooke, 2005;Okubo and Schulz, 2005;Fattaruso et al, 2016). However, these metrics can lead to conflicting predictions about both the sites of new fracture nucleation and the direction of fracture growth (e.g., Madden et al, 2017;McBeck et al, 2017McBeck et al, , 2020b. If preexisting fracture propagation is the dominant mode of development rather than fracture nucleation, then metrics that determine the conditions under which preexisting fractures will grow, such as the critical stress intensity factor (Isida, 1971), and the direction of fault growth, such as Coulomb shear stress, tensile stress, and energy optimization (e.g., Pollard and Aydin, 1988;Müller, 1998;Mary et al, 2013;Madden et al, 2017;McBeck et al, 2017), may provide more accurate predictions of fault network development than nucleation criteria.…”

Section: Introductionmentioning

confidence: 99%

The competition between fracture nucleation, propagation, and coalescence in dry and water-saturated crystalline rock

2021

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Abstract. The continuum of behavior that emerges during fracture network development in crystalline rock may be categorized into three end-member modes: fracture nucleation, isolated fracture propagation, and fracture coalescence. These different modes of fracture growth produce fracture networks with distinctive geometric attributes, such as clustering and connectivity, that exert important controls on permeability and the extent of fluid–rock interactions. To track how these modes of fracture development vary in dominance throughout loading toward failure and thus how the geometric attributes of fracture networks may vary under these conditions, we perform in situ X-ray tomography triaxial compression experiments on low-porosity crystalline rock (monzonite) under upper-crustal stress conditions. To examine the influence of pore fluid on the varying dominance of the three modes of growth, we perform two experiments under nominally dry conditions and one under water-saturated conditions with 5 MPa of pore fluid pressure. We impose a confining pressure of 20–35 MPa and then increase the differential stress in steps until the rock fails macroscopically. After each stress step of 1–5 MPa we acquire a three-dimensional (3D) X-ray adsorption coefficient field from which we extract the 3D fracture network. We develop a novel method of tracking individual fractures between subsequent tomographic scans that identifies whether fractures grow from the coalescence and linkage of several fractures or from the propagation of a single fracture. Throughout loading in all of the experiments, the volume of preexisting fractures is larger than that of nucleating fractures, indicating that the growth of preexisting fractures dominates the nucleation of new fractures. Throughout loading until close to macroscopic failure in all of the experiments, the volume of coalescing fractures is smaller than the volume of propagating fractures, indicating that fracture propagation dominates coalescence. Immediately preceding failure, however, the volume of coalescing fractures is at least double the volume of propagating fractures in the experiments performed at nominally dry conditions. In the water-saturated sample, in contrast, although the volume of coalescing fractures increases during the stage preceding failure, the volume of propagating fractures remains dominant. The influence of stress corrosion cracking associated with hydration reactions at fracture tips and/or dilatant hardening may explain the observed difference in fracture development under dry and water-saturated conditions.

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“…GROW accurately simulates the propagation path and linkage of two nearby fracture tips separated by a releasing step [63], the propagation of wing cracks from inclined fractures observed in uniaxial and biaxial compression experiments [46], the coalescence of hundreds of fractures observed in uniaxial compression experiments [64], and the development of thrust faults in accretionary prisms [65].…”

Section: Numerical Model Designmentioning

confidence: 99%

“…Recent work describes in detail the key algorithms of GROW [64,65]. In summary, in the single run mode of fracture growth, the fracture tip that grows during a given time step is the tip with the highest sum of the absolute value of the mode-I and mode-II stress intensity factors.…”

Section: Numerical Model Designmentioning

confidence: 99%

Deformation evolves from shear to extensile in rocks due to energy optimization

McBeck

Cordonnier

Cooke

et al. 2023

Preprint

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Determining how fracture network development leads to macroscopic failure in heterogeneous materials may help estimate the timing of failure in rocks in the upper crust as well as in engineered structures. The proportion of extensile and shear deformation produced by fracture development indicates the appropriate failure criteria to apply, and thus is a key constraint in such an effort. Here, we measure the volume proportion of extensile and shear fractures using the orientation of the fractures that develop in triaxial compression experiments in which fractures are identified using dynamic in situ synchrotron X-ray imaging. The fracture orientations transition from shear to extensile approaching macroscopic, system-size failure. Numerical models suggest that this transition occurs because the fracture networks evolve in order to optimize the total mechanical efficiency of the system. Our results provide a physical interpretation of the empirical internal friction coefficient in rocks.

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Predicting the propagation and interaction of frontal accretionary thrust faults with work optimization

Cited by 6 publications

References 34 publications

Strain Localization Patterns and Thrust Propagation in 3‐D Discrete Element Method (DEM) Models of Accretionary Wedges

Strain Localization Patterns and Thrust Propagation in 3‐D Discrete Element Method (DEM) Models of Accretionary Wedges

The competition between fracture nucleation, propagation, and coalescence in dry and water-saturated crystalline rock

Deformation evolves from shear to extensile in rocks due to energy optimization

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