David A Lockner
David Lockner is a geophysicist in the Earthquake Science Center.
Science and Products
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Strengths of serpentinite gouges at elevated temperatures
Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughl
Authors
Diane E. Moore, D. A. Lockner, S. Ma, R. Summers, J. D. Byerlee
A test of the double-shearing model of flow for granular materials
The double-shearing model of flow attributes plastic deformation in granular materials to cooperative slip on conjugate Coulomb shears (surfaces upon which the Coulomb yield condition is satisfied). The strict formulation of the double-shearing model then requires that the slip lines in the material coincide with the Coulomb shears. Three different experiments that approximate simple shear deforma
Authors
J. C. Savage, D. A. Lockner
Failure in laboratory fault models in triaxial tests
A model of a fault in the Earth is a sand-filled saw cut in a granite cylinder subjected to a triaxial test. The saw cut is inclined at an angle a to the cylinder axis, and the sand filling is intended to represent gouge. The triaxial test subjects the granite cylinder to a constant confining pressure and increasing axial stress to maintain a constant rate of shortening of the cylinder. The requir
Authors
J. C. Savage, D. A. Lockner, J. D. Byerlee
Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault?
Chrysotile-bearing serpentinite is a constituent of the San Andreas fault zone in central and northern California. At room temperature, chrysotile gouge has a very low coefficient of friction (μ ≈ 0.2), raising the possibility that under hydrothermal conditions μ might be reduced sufficiently (to ≤0.1) to explain the apparent weakness of the fault. To test this hypothesis, we measured the friction
Authors
Diane E. Moore, D. A. Lockner, R. Summers, M. Shengli, J. D. Byerlee
Is internal friction friction?
Mogi [1974] proposed a simple model of the incipient rupture surface to explain the Coulomb failure criterion. We show here that this model can plausibly be extended to explain the Mohr failure criterion. In Mogi's model the incipient rupture surface immediately before fracture consists of areas across which material integrity is maintained (intact areas) and areas across which it is not (cracks).
Authors
J. C. Savage, J. D. Byerlee, D. A. Lockner
Sample characterizations and strength measurements of serpentinite gouges
No abstract available.
Authors
Diane E. Moore, D. A. Lockner, R. Summers, J. D. Byerlee
High-temperature permeability studies; 1, Permeability of granite and novaculite at 300 degrees to 500 degrees C
No abstract available.
Authors
Diane E. Moore, L.Q. Liu, D. A. Lockner, R.S. Summers, J. D. Byerlee
Frictional slip of granite at hydrothermal conditions
To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0
Authors
M.L. Blanpied, D. A. Lockner, J. D. Byerlee
An earthquake instability model based on faults containing high fluid-pressure compartments
It has been proposed that large strike-slip faults such as the San Andreas contain water in seal-bounded compartments. Arguments based on heat flow and stress orientation suggest that in most of the compartments, the water pressure is so high that the average shear strength of the fault is less than 20 MPa. We propose a variation of this basic model in which most of the shear stress on the fault i
Authors
D. A. Lockner, J. D. Byerlee
The role of microcracking in shear-fracture propagation in granite
Microcracking related to the formation of a laboratory shear fracture in a cylinder of Westerly granite has been investigated using image-analysis computer techniques. Well away from the fracture, the deformed granite has about twice the crack density of undeformed granite. The microcrack density increases dramatically in a process zone that surrounds the fracture tip, and the fracture tip itself
Authors
Diane E. Moore, D. A. Lockner
Reduction of permeability in granite at elevated temperatures
The addition of hydrothermal fluids to heated, intact granite leads to permeability reductions in the temperature range of 300?? to 500??C, with the rate of change generally increasing with increasing temperature. The addition of gouge enhances the rate of permeability reduction because of the greater reactivity of the fine material. Flow rate is initially high in a throughgoing fracture but event
Authors
Diane E. Moore, D. A. Lockner, J. D. Byerlee
Triaxial testing of Lopez Fault gouge at 150 MPa mean effective stress
Triaxial compression experiments were performed on samples of natural granular fault gouge from the Lopez Fault in Southern California. This material consists primarily of quartz and has a self-similar grain size distribution thought to result from natural cataclasis. The experiments were performed at a constant mean effective stress of 150 MPa, to expose the volumetric strains associated with she
Authors
D.R. Scott, D. A. Lockner, J. D. Byerlee, C.G. Sammis
Science and Products
Filter Total Items: 13
No Result Found
Filter Total Items: 113
Strengths of serpentinite gouges at elevated temperatures
Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughl
Authors
Diane E. Moore, D. A. Lockner, S. Ma, R. Summers, J. D. Byerlee
A test of the double-shearing model of flow for granular materials
The double-shearing model of flow attributes plastic deformation in granular materials to cooperative slip on conjugate Coulomb shears (surfaces upon which the Coulomb yield condition is satisfied). The strict formulation of the double-shearing model then requires that the slip lines in the material coincide with the Coulomb shears. Three different experiments that approximate simple shear deforma
Authors
J. C. Savage, D. A. Lockner
Failure in laboratory fault models in triaxial tests
A model of a fault in the Earth is a sand-filled saw cut in a granite cylinder subjected to a triaxial test. The saw cut is inclined at an angle a to the cylinder axis, and the sand filling is intended to represent gouge. The triaxial test subjects the granite cylinder to a constant confining pressure and increasing axial stress to maintain a constant rate of shortening of the cylinder. The requir
Authors
J. C. Savage, D. A. Lockner, J. D. Byerlee
Strength of chrysotile-serpentinite gouge under hydrothermal conditions: Can it explain a weak San Andreas fault?
Chrysotile-bearing serpentinite is a constituent of the San Andreas fault zone in central and northern California. At room temperature, chrysotile gouge has a very low coefficient of friction (μ ≈ 0.2), raising the possibility that under hydrothermal conditions μ might be reduced sufficiently (to ≤0.1) to explain the apparent weakness of the fault. To test this hypothesis, we measured the friction
Authors
Diane E. Moore, D. A. Lockner, R. Summers, M. Shengli, J. D. Byerlee
Is internal friction friction?
Mogi [1974] proposed a simple model of the incipient rupture surface to explain the Coulomb failure criterion. We show here that this model can plausibly be extended to explain the Mohr failure criterion. In Mogi's model the incipient rupture surface immediately before fracture consists of areas across which material integrity is maintained (intact areas) and areas across which it is not (cracks).
Authors
J. C. Savage, J. D. Byerlee, D. A. Lockner
Sample characterizations and strength measurements of serpentinite gouges
No abstract available.
Authors
Diane E. Moore, D. A. Lockner, R. Summers, J. D. Byerlee
High-temperature permeability studies; 1, Permeability of granite and novaculite at 300 degrees to 500 degrees C
No abstract available.
Authors
Diane E. Moore, L.Q. Liu, D. A. Lockner, R.S. Summers, J. D. Byerlee
Frictional slip of granite at hydrothermal conditions
To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0
Authors
M.L. Blanpied, D. A. Lockner, J. D. Byerlee
An earthquake instability model based on faults containing high fluid-pressure compartments
It has been proposed that large strike-slip faults such as the San Andreas contain water in seal-bounded compartments. Arguments based on heat flow and stress orientation suggest that in most of the compartments, the water pressure is so high that the average shear strength of the fault is less than 20 MPa. We propose a variation of this basic model in which most of the shear stress on the fault i
Authors
D. A. Lockner, J. D. Byerlee
The role of microcracking in shear-fracture propagation in granite
Microcracking related to the formation of a laboratory shear fracture in a cylinder of Westerly granite has been investigated using image-analysis computer techniques. Well away from the fracture, the deformed granite has about twice the crack density of undeformed granite. The microcrack density increases dramatically in a process zone that surrounds the fracture tip, and the fracture tip itself
Authors
Diane E. Moore, D. A. Lockner
Reduction of permeability in granite at elevated temperatures
The addition of hydrothermal fluids to heated, intact granite leads to permeability reductions in the temperature range of 300?? to 500??C, with the rate of change generally increasing with increasing temperature. The addition of gouge enhances the rate of permeability reduction because of the greater reactivity of the fine material. Flow rate is initially high in a throughgoing fracture but event
Authors
Diane E. Moore, D. A. Lockner, J. D. Byerlee
Triaxial testing of Lopez Fault gouge at 150 MPa mean effective stress
Triaxial compression experiments were performed on samples of natural granular fault gouge from the Lopez Fault in Southern California. This material consists primarily of quartz and has a self-similar grain size distribution thought to result from natural cataclasis. The experiments were performed at a constant mean effective stress of 150 MPa, to expose the volumetric strains associated with she
Authors
D.R. Scott, D. A. Lockner, J. D. Byerlee, C.G. Sammis