About

Judith Chester is a professor at Texas A&M University College of Arts and Sciences, specializing in Geology and Geophysics. She has held the title of Mollie B. & Richard A. Williford Professor in Petroleum Geology from 2019 to 2023 and serves as Vice Chair of the Science Planning Committee for the Southern California Earthquake Center (SCEC) since 2014. Her research interests focus on deformation and alteration reactions during faulting, emphasizing their importance to earthquake nucleation and rupture propagation in the continental crust. She investigates mechanisms of creep compaction of reservoir rock and the mechanics of fold-fault interaction in anisotropic rock. Her projects include geologic constraints on earthquake physics and structural-petrologic characterization of fault zones, such as the San Andreas Fault Zone. Dr. Chester holds a Ph.D., M.S., and B.S. in Geology from Texas A&M University and the University of California at Los Angeles. Her notable awards include the Paul G. Silver Award for Outstanding Scientific Service from the AGU in 2019 and the El Paso Energy Foundation Faculty Achievement Award from Texas A&M University in 2003.

Research topics

• Materials science
• Composite material
• Geotechnical engineering
• Geology
• Metallurgy
• Thermodynamics
• Mechanics

Selected publications

• Investigating Dynamic Weakening in Laboratory Faults Using Multi‐Scale Flash Heating Coupled With mm‐Scale Contact Evolution

  Journal of Geophysical Research Solid Earth · 2023-12-01 · 6 citations

  articleOpen accessSenior author

  Abstract Flash‐weakening models typically show good agreement with the total magnitude of weakening in high‐speed rock friction experiments, however deviations during the acceleration and deceleration phases, and at low and intermediate sliding velocities, remain unresolved. Here, we incorporate inhomogeneous mm‐scale normal stress evolution into a model for flash heating and weakening to resolve outstanding transient and hysteretic friction observed in laboratory experiments and to identify unique solutions to constitutive parameters. We conduced 37 rock friction experiments on Westerly granite using a high‐speed biaxial apparatus outfitted with a high‐speed infrared camera. We initiated velocity steps from quasi‐static rates of 1 mm/s to sliding velocities ranging from 300 to 900 mm/s and conducted both constant‐ and decreasing‐velocity tests following the velocity step. Two sliding surfaces geometries were used to control mm‐scale life‐times and rest‐times. Constant‐strength sliding is achieved within 2–3 mm of initiating the velocity step in all constant‐velocity experiments. Macroscopic surface temperature is inhomogeneous and increases with slip distance, velocity, and decreasing rest‐time. Weakening increases with sliding velocity and decreasing rest‐time. We combine thermal models with measured surface temperatures to constrain the evolution of local normal stress at the mm‐scale and incorporate this evolution into a flash‐weakening model that considers weakening at both the µm‐ and mm‐scale. The flash‐weakening model improves when the effects of mm‐scale wear processes are incorporated and multi‐scale weakening is considered, however some transient friction remains undescribed. Models will be advanced by further incorporating wear processes and by considering processes at the mm‐scale and above.

  PublisherOA PDFDOI

• Grain-boundary processes and semibrittle behavior of salt-rock

  2022-06-27

  book-chapter

  Grain-boundary microcracking, sliding, indentation, and healing have been shown to impact salt-rock bulk deformation. An improved understanding of the combined action of grain-boundary processes is necessary for accurate interpretation of salt-rock mechanical behavior in both natural and engineering contexts. We prepared granular, low-porosity, work-hardened salt-rocks (∼300 ppm water) for triaxial stress-cycling experiments at low confining pressure to investigate semibrittle behavior and effective stress. We used optical microscopy to characterize grain-scale structure. Semibrittle flow involves coupled grain-boundary sliding and wing-crack opening accommodated by indentation via intragranular dislocation glide. Grain-boundary sliding is frictional at higher strain rates, but the associated dispersion of water from fluid inclusions along boundaries can activate linear-viscous, fluid-assisted, diffusional sliding at lower strain rates (<10-8 s-1). The combined action of these mechanisms leads to pressureand time-dependent behaviors including anelasticity and hysteresis. In addition, we conducted cyclic poreand confining-pressure tests to demonstrate that during semibrittle flow, strength depends on differential pressure consistent with the Terzaghi’s effective stress law. This behavior may be explained by combined operation of pressure-independent intracrystalline-plastic mechanisms and transmission of pore pressure at grain boundaries via thin fluid films. Our study indicates coupled microprocesses are key to understanding semibrittle behavior of salt-rocks.

  PublisherDOI

• Fabric evolution and crack propagation in salt during consolidation and cyclic compression tests

  Acta Geotechnica · 2021-01-02 · 7 citations

  article
  PublisherDOI

• Test of the Effective Stress Law for Semibrittle Deformation Using Isostatic and Triaxial Load Paths

  Journal of Geophysical Research Solid Earth · 2021-04-01 · 1 citations

  articleSenior author

  Abstract For brittle friction and rock deformation, the coefficient α in the general effective stress relation σ e = σ − αP p can be approximated as unity with sufficient accuracy. However, it is uncertain if α deviates from unity for semibrittle flow when both brittle and intracrystalline‐plastic deformation is involved. We conducted triaxial and isostatic compression experiments on synthetic salt‐rocks (∼300 ppm water) at room temperature to test the effective stress relation in the semibrittle regime using silicone oil and argon gas as pore fluids. Confining and pore pressures were cycled while their difference (differential pressure) was kept constant, such that changes in the mechanical behavior would indicate deviation of α from unity. Microstructural observations were used to determine the dependence of α on true area of grain contact from asperity yielding. In triaxial compression experiments, semibrittle flow involves grain boundary cracking and sliding, and intragranular dislocation glide and cracking. Flow strength remains constant for changes in pore fluid pressure of more than two orders of magnitude. In isostatic compression experiments, samples show combined processes of microcracking, grain boundary sliding, dislocation glide, and fluid‐assisted grain boundary migration recrystallization. Volumetric strain depends directly on the differential pressures (i.e., α equals one). Analysis of grain‐contact area in both experiments indicates that α is independent of the true area of contact defined by plastic yielding at grain boundaries. The observation of α effectively equals one may be explained by operation of pressure‐independent intracrystalline‐plastic mechanisms and transmission of pore pressure at grain boundaries through thin fluid films.

  PublisherDOI

• Characterizing the Distribution of Temperature and Normal Stress on Flash Heated Granite Surfaces at Seismic Slip Rates

  Journal of Geophysical Research Solid Earth · 2021-05-01 · 13 citations

  articleOpen accessSenior author

  Abstract At seismic slip rates, flash‐weakening can significantly reduce the coefficient of friction, and the magnitude of weakening increases with surface temperature. To quantify the distribution of flash temperature, high‐speed double‐direct shear experiments were conducted on Westerly granite blocks using velocity steps from 1 mm/s to 900 mm/s at 9 MPa normal stress. We employed a high‐speed infrared camera to measure surface temperatures on the moving block during sliding, and utilized a novel sliding‐surface geometry to control the mm‐scale contact history. Following the initial weakening upon the velocity step, the blocks slide at a constant coefficient of friction. Surface temperatures are inhomogeneously distributed across the sliding surface, and increase with displacement. To determine the local normal stress distribution at the mm‐scale, we combine a one‐dimensional thermal model with conventional flash‐weakening models that incorporate a surface temperature‐dependence informed by the controlled, mm‐scale contact history. Early contacts experience local normal stress exceeding 40 times the applied normal stress. As sliding progresses, the local normal stress at the hottest contacts decreases as contact area increases, leading to local normal stresses ranging from 2 to 6 times the applied normal stress on most contacts by 30 mm of slip. Increases in surface temperature, which would decrease the coefficient of friction, are buffered by wear processes that increase contact area and decrease the local normal stress. Treatments of flash heating are advanced by incorporating improved characterization of the state of the sliding surface at the mm and larger scales during sliding.

  PublisherOA PDFDOI

• Coupled Brittle and Viscous Micromechanisms Produce Semibrittle Flow, Grain‐Boundary Sliding, and Anelasticity in Salt‐Rock

  Journal of Geophysical Research Solid Earth · 2021 · 16 citations

  • Materials science
  • Composite material

  Abstract The operation of fracture, diffusion, and intracrystalline‐plastic micromechanisms during semibrittle deformation of rock is directly relevant to understanding mechanical behavior across the brittle‐plastic transition in the crust. An outstanding question is whether (1) the micromechanisms of semibrittle flow can be considered to operate independently, as represented in typical crustal strength profiles across the brittle to plastic transition, or (2) the micromechanisms are coupled such that the transition is represented by a distinct rheology with dependency on effective pressure, temperature, and strain rate. We employ triaxial stress‐cycling experiments to investigate elastic‐plastic and viscoelastic behaviors during semibrittle flow in two distinctly different monomineralic, polycrystalline, synthetic salt‐rocks. During semibrittle flow at high differential stress, granular, low‐porosity, work‐hardened salt‐rocks deform predominantly by grain‐boundary sliding and wing‐crack opening accompanied by minor intragranular dislocation glide. In contrast, fully annealed, near‐zero porosity salt‐rocks flow at lower differential stress by intragranular dislocation glide accompanied by grain‐boundary sliding and opening. Grain‐boundary sliding is frictional during semibrittle flow at higher strain rates, but the associated dispersal of water from fluid inclusions along boundaries can activate fluid‐assisted diffusional sliding at lower strain rates. Changes in elastic properties with semibrittle flow largely reflect activation of sliding along closed grain boundaries. Observed microstructures, pronounced hysteresis and anelasticity during cyclic stressing after semibrittle flow, and stress relaxation behaviors indicate coupled operation of micromechanisms leading to a distinct rheology (hypothesis 2 above).

  PublisherDOI

• Micromechanical modeling for rate‐dependent behavior of salt rock under cyclic loading

  International Journal for Numerical and Analytical Methods in Geomechanics · 2020 · 11 citations

  • Materials science
  • Composite material
  • Geotechnical engineering

  Summary The dependence of rock behavior on the deformation rate is still not well understood. In salt rock, the fundamental mechanisms that drive the accumulation of irreversible deformation, the reduction of stiffness, and the development of hysteresis during cyclic loading are usually attributed to intracrystalline plasticity and diffusion. We hypothesize that at low pressure and low temperature, the rate‐dependent behavior of salt rock is governed by water‐assisted diffusion along grain boundaries. Accordingly, a chemo‐mechanical homogenization framework is proposed in which the representative elementary volume (REV) is viewed as a homogeneous polycrystalline matrix that contains sliding grain‐boundary cracks. The slip is related to the mass of salt ions that diffuse along the crack surface. The relationship between fluid inclusion‐scale and REV‐scale stresses and strains is established by using the Mori–Tanaka homogenization scheme. It is noted from the model that a lower strain rate and a larger number of sliding cracks enhance stiffness reduction and hysteresis. Thinner sliding cracks (i.e., thinner brine films) promote stiffness reduction and accelerate stress redistributions. The larger the volume fraction of the crack inclusions, the larger the REV deformation and the larger the hysteresis. Results presented in this study shed light on the mechanical behavior of salt rock that is pertinent to the design of geological storage facilities that undergo cyclic unloading, which could help optimize the energy production cycle with low carbon emissions.

  PublisherDOI

• Mechanisms of Anisotropy in Salt Rock Upon Microcrack Propagation

  Rock Mechanics and Rock Engineering · 2020 · 27 citations

  Senior authorCorresponding
  • Materials science
  • Mechanics
  • Geotechnical engineering
  PublisherDOI

• Changes in anelasticity and grain boundary processes with stress cycling in semibrittle salt-rocks

  2020-05-28

  preprintOpen access

  The coupled operation of fracture, diffusion, and intracrystalline-plastic micromechanisms during semibrittle deformation of rock is directly relevant to understanding crustal processes such as earthquake rupture at the base of the seismogenic zone and failure of salt caverns for energy storage. Triaxial stress-cycling experiments are used to investigate elastic-plastic and viscoelastic behaviors in two synthetic salt-rocks deformed at room temperature and low confinement. During semibrittle flow at high differential stress, porous, granular, work-hardened samples deform predominantly by grain boundary sliding and opening accompanied by minor intragranular cracking and dislocation glide. In contrast, fully annealed, near-zero porosity samples deform at lower differential stress by dislocation glide, grain-boundary sliding and opening accompanied by minor intragranular cracking. During high-stress cycling and semibrittle flow, grain boundary sliding is predominantly frictional; but, associated dispersal of water previously trapped in fluid inclusions can activate fluid-assisted diffusional sliding along grain boundaries at low strain rates. Young’s modulus and Poisson’s ratio are largely controlled by the behavior of closed grain boundaries. Grain boundary sliding accommodated by fluid-assisted diffusion leads to nearly complete stress relaxation after semibrittle flow, and in subsequent low-stress cycling both viscoelasticity and pronounced hysteresis are observed. However, such time-dependent effects vanish with grain boundary healing over days-long holds at low differential stress. Experimental results suggest that within the semibrittle regime, high-stress events can lead to significant transient reduction in viscosity and related phenomena.

  PublisherDOI

• Test of the effective stress law for semibrittle flow in synthetic salt-rock

  AGU Fall Meeting Abstracts · 2019-12-01

  articleSenior author
  Publisher

Recent grants

• Geologic Constraints on Fracture Energy of the San Andreas Fault

  NSF · $303k · 2005–2011

• Collaborative Research: Influence of Structure, Composition and Fluid-Rock Chemistry on Mode of Slip in the San Andreas Fault Zone at SAFOD

  NSF · $201k · 2007–2012

• EarthScope SAFOD Management Office for Physical Samples

  NSF · $532k · 2013–2020

Frequent coauthors

• F. M. Chester

  Texas A&M University

  71 shared

• A. K. Kronenberg

  Texas A&M University

  16 shared

• Jihui Ding

  Nanjing Forestry University

  14 shared

• Chloé Arson

  Georgia Institute of Technology

  13 shared

• O. Dor

  11 shared

• Xianda Shen

  Tongji University

  10 shared

• Stephen L. Karner

  ExxonMobil (United States)

  10 shared

• Melodie French

  Rice University

  9 shared

Education

• Ph.D., Geology

  University of Texas at Austin

  1990

• M.S., Geology

  University of Texas at Austin

  1985

• B.S., Geology

  University of Texas at Austin

  1983

Awards & honors

• Paul G. Silver Award for Outstanding Scientific Service, AGU…
• National Science Foundation EarthScope Speaker (2008-2009)
• El Paso Energy Foundation Faculty Achievement Award, College…
• Montague-Center for Teaching Excellence Scholar, Texas A&M U…