Testing constitutive equations for brittle‐ductile deformation associated with faulting in granitic rock

Nevitt, J. M.; Warren, J. M.; Pollard, David D.

doi:10.1002/2017jb014000

Cited by 46 publications

(7 citation statements)

References 119 publications

(191 reference statements)

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“…Schematic “Christmas tree” diagram of mineral flow laws in granitoid rock illustrating the transition from brittle to semibrittle to ductile bulk deformation. Modified from Jammes et al () and Nevitt et al ().…”

Section: Introductionmentioning

confidence: 99%

The Impact of Rheology on the Transition From Stick‐Slip to Creep in a Semibrittle Analog

Birren

Reber

2019

JGR Solid Earth

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Faults can release energy via a variety of different slip mechanisms ranging from steady creep to fast and destructive earthquakes. Tying the rheology of the crust to various slip dynamics is important for our understanding of plate tectonics and earthquake generation. Here we propose that the interplay of fractures and viscous flow leads to a spectrum between stick‐slip and creep. We use an elasto‐visco‐plastic rock analog (Carbopol U‐21) where we vary the yield stress to investigate its impact on slip dynamics in shear experiments. The experiments are performed using a simple shear apparatus, which provides distributed shear across the entire width of the experiment and allows in situ observations of deformation. We record force and displacement during deformation and use time lapse photography to document fracture development. A low yield stress (25 Pa) leads to creep dynamics in the absence of fractures. An intermediate yield stress (144 Pa) leads to the development and interaction of opening (mode I) and shear (mode II) fractures. This interaction leads to a spectrum in slip dynamics ranging from creep to stick‐slip. A high yield stress (357 Pa) results in the development of many mode I fractures and a deformation signal dominated by stick‐slip. These results show that bulk yield stress, fracture formation, and slip dynamics are closely linked and can lead to a continuum between creep and stick‐slip. We suggest that rheology should be considered as an additional mechanism to explain the broad range of slip dynamics in natural faults.

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Section: Introductionmentioning

confidence: 99%

The Impact of Rheology on the Transition From Stick‐Slip to Creep in a Semibrittle Analog

Birren

Reber

2019

JGR Solid Earth

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“…Although there are many implicit simplifications when using a numerical model to approximate geologic textures, it is worthwhile to help establish constitutive laws in natural faults (e.g., Nevitt et al, , ). The single clast‐in‐matrix mesh geometry, simplifications of deformation mechanisms from field observations, and scaled natural parameters represent the main limitations of this model.…”

Section: Discussionmentioning

confidence: 99%

Fault Initiation in Serpentinite

Melosh

2019

Geochem Geophys Geosyst

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Serpentinite fault rheology is fundamental to tectonic and earthquake processes, yet links between deformation textures and strength evolution during fault initiation are poorly constrained. Here I present field and petrographic microstructural observations of unsheared and sheared serpentinite that demonstrate a progression of fault development. I compliment observations with a clast‐size distribution analysis to investigate the evolution of fault rigidity and a numerical model to query the stress distribution of a clast‐in‐matrix geometry. Unsheared microstructures reveal well‐aligned, elongate serpentine in the matrix and short, randomly oriented serpentine in clasts. Sheared matrix displays cataclastic textures, discrete brittle surfaces, dissolution bands, and ductile textures defined by anastomosing networks of well‐aligned, fine‐grained serpentine. During fault initiation, matrix serpentine anisotropy promotes slip on basal planes or fiber aggregates, and clast‐on‐clast interactions drive a high bulk viscosity prone to stick‐slip behavior. As deformation progresses, clast fracturing is focused at clast tips, and smaller clasts are preferentially removed by dissolution‐precipitation processes, increasing the relative abundance of matrix and promoting fault creep. Strain is continually focused in the matrix and as clast content reduces the bulk viscosity drops. This study reveals that viscosity contrasts formed by primary serpentinization textures are a major driver for the development and strength evolution of faults. On a continental‐scale, similar processes may govern earthquake distributions, fault growth, and segmentation patterns on young, serpentinite‐hosted faults.

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“…Plasticity Criterion. Considering the influence of the microstructure on rock mechanical strength, the von Mises yield criterion has been widely applied in the microscale deformation-fracture process of the rock, which are adopted for determining the plastic deformation of the rock skeleton [37][38][39]. e criterion states that yielding begins when the elastic energy of distortion reaches a critical value [40].…”

Section: Mathematical Modelmentioning

confidence: 99%

Effects of Pore Structure on Sandstone Mechanical Properties Based on Micro‐CT Reconstruction Model

Song

Zheng

Wang

et al. 2020

Advances in Civil Engineering

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As porous, heterogeneous, and anisotropic material, the microscopic structure of the rock has a significant influence on its mechanical properties. Rare studies were devoted to this area using pore scale modeling and simulations. In this paper, different types of sandstones are imaged using micro-CT technology. The rock porosity is obtained by filtering, binarization, and threshold segmentation. The texture coefficient (TC) and the tortuosity of the rock skeleton are calculated by open source program, where the tortuosity of the rock skeleton is firstly used to characterize the microscopic structure of the rock. Combining with the rock mechanics parameters obtained in the laboratory, the simulation of uniaxial compression is performed on the reconstructed pore scale rock finite element mesh model by ANSYS software. Young’s modulus, compressive strength, yield strength, shear modulus, and other related parameters obtained by numerical simulation are adopted to determine the optimal representative volume element (RVE) size. Moreover, the effects of microscopic structure characteristics on the mechanical properties of the rock are studied quantitatively. The results indicate that the averaged von Mises stress distribution, displacement field, and plastic strain field of rocks show anisotropy and heterogeneity. The stress concentration and the X-shaped conjugate plastic shear zone are investigated. The samples of S1∼S4 reach the elastic limit and enters the plastic yield state, when the strain is about 0.5%. And the critical yield strain of samples S5300-1∼S5400-2 is about 1%. Then, the quantitative relationships between porosity, TC, tortuosity of rock skeleton and rock mechanics parameters of digital rock samples are established and analyzed. The tortuosity of the rock skeleton is highly correlated with the mechanical parameters of the rock, i.e., Young’s modulus (R2 = 0.95), compressive strength (R2 = 0.94), yield strength (R2 = 0.92), and shear modulus (R2 = 0.94), which is believed to be more feasible to reveal the impacts of the microstructure of the rock on its mechanical properties.

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Testing constitutive equations for brittle‐ductile deformation associated with faulting in granitic rock

Cited by 46 publications

References 119 publications

The Impact of Rheology on the Transition From Stick‐Slip to Creep in a Semibrittle Analog

The Impact of Rheology on the Transition From Stick‐Slip to Creep in a Semibrittle Analog

Fault Initiation in Serpentinite

Effects of Pore Structure on Sandstone Mechanical Properties Based on Micro‐CT Reconstruction Model

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