David A Lockner
David Lockner is a geophysicist in the Earthquake Science Center.
Science and Products
Filter Total Items: 13
No Result Found
Filter Total Items: 112
Fracture in Westerly granite under AE feedback and constant strain rate loading: Nucleation, quasi-static propagation, and the transition to unstable fracture propagation
New observations of fracture nucleation are presented from three triaxial compression experiments on intact samples of Westerly granite, using Acoustic Emission (AE) monitoring. By conducting the tests under different loading conditions, the fracture process is demonstrated for quasi-static fracture (under AE Feedback load), a slowly developing unstable fracture (loaded at a 'slow' constant strain
Authors
B.D. Thompson, R.P. Young, D. A. Lockner
Mineralogical characterization of protolith and fault rocks from the SAFOD Main Hole
Washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the San Andreas Fault Observatory at Depth (SAFOD). Both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology, P-T conditions, deformation mechanisms, and fluid composition and abundance. Regions of distinct neominerali
Authors
J.G. Solum, S.H. Hickman, D. A. Lockner, Diane E. Moore, B.A. van der Pluijm, A.M. Schleicher, J.P. Evans
Frictional strength of cuttings and core from SAFOD drillhole phases 1 and 2
We investigated the frictional properties of drill cuttings and core obtained from 1.85-3.1 km true vertical depth in the SAFOD scientific borehole in central California. Triaxial frictional sliding experiments were conducted on samples from primary lithologic traits and significant shear zones, including the inferred active trace of the San Andreas fault. The samples were deformed at room tempera
Authors
S. Tembe, D. A. Lockner, J.G. Solum, C.A. Morrow, T.-F. Wong, Diane E. Moore
Observations of premonitory acoustic emission and slip nucleation during a stick slip experiment in smooth faulted Westerly granite
To investigate laboratory earthquakes, stick-slip events were induced on a saw-cut Westerly granite sample by triaxial loading at 150 MPa confining pressure. Acoustic emissions (AE) were monitored using an innovative continuous waveform recorder. The first motion of each stick slip was recorded as a large-amplitude AE signal. These events source locate onto the saw-cut fault plane, implying that t
Authors
B.D. Thompson, R.P. Young, D. A. Lockner
High-pressure rock-physics laboratories investigate earthquake processes
No abstract available.
Authors
C.A. Morrow, D. A. Lockner
The coefficient of friction of chrysotile gouge at seismogenic depths
We report new strength data for the serpentine mineral chrysotile at effective normal stresses, σn between 40 and 200 MPa in the temperature range 25°-280°C. Overall, the coefficient of friction, μ (= shear stress/effective normal stress) of water-saturated chrysotile gouge increases both with increasing temperature and σn, but the rates vary and the temperature-related increases begin at ~100°C.
Authors
Diane E. Moore, D. A. Lockner, H. Tanaka, K. Iwata
Crystallographic controls on the frictional behavior of dry and water-saturated sheet structure minerals
We compare the frictional strengths of 17 sheet structure mineral powders, measured under dry and water-saturated conditions, to identify the factors that cause many of them to be relatively weak. The dry coefficient of friction μ ranges upward from 0.2 for graphite, leveling off at 0.8 for margarite, clintonite, gibbsite, kaolinite, and lizardite. The values of μ (dry) correlate directly with cal
Authors
Diane E. Moore, D. A. Lockner
Why earthquakes correlate weakly with the solid Earth tides: Effects of periodic stress on the rate and probability of earthquake occurrence
We provide an explanation why earthquake occurrence does not correlate well with the daily solid Earth tides. The explanation is derived from analysis of laboratory experiments in which faults are loaded to quasiperiodic failure by the combined action of a constant stressing rate, intended to simulate tectonic loading, and a small sinusoidal stress, analogous to the Earth tides. Event populations
Authors
N.M. Beeler, D. A. Lockner
Anisotropic changes in P-wave velocity and attenuation during deformation and fluid infiltration of granite
Fluid infiltration and pore fluid pressure changes are known to have a significant effect on the occurrence of earthquakes. Yet, for most damaging earthquakes, with nucleation zones below a few kilometers depth, direct measurements of fluid pressure variations are not available. Instead, pore fluid pressures are inferred primarily from seismic-wave propagation characteristics such as Vp/Vs ratio,
Authors
S. A. Stanchits, D. A. Lockner, A.V. Ponomarev
32 - Rock failure and earthquakes
This chapter summarizes experimental observations and related theoretical developments of faulted and intact rock properties related to earthquake nucleation, failure and dynamic slip. We will be concerned primarily with earthquakes occurring in the brittle crust. Intermediate and deep-focus earthquakes have unique mechanical considerations that are discussed in Section 7. We focus on repeatable l
Authors
David A. Lockner, Nicholas M. Beeler
Undrained poroelastic response of sandstones to deviatoric stress change
Deformation of porous crustal rock through diagenesis, tectonic loading, or other processes can change pore volume and affect fluid pressure. The largest stress-induced pore pressure changes occur when fluid is trapped in pores in an “undrained” condition. We have measured the undrained poroelastic response of two sandstones to changes in mean and deviatoric stress. Pore pressure was found to resp
Authors
D. A. Lockner, S. A. Stanchits
How brucite may affect the frictional properties of serpentinite
The frictional strength of brucite gouge has been measured at hydrothermal conditions to 450°C. At room temperature, brucite has a coefficient of friction, μ ≈ 0.30, making it one of the weakest minerals identified to date. With increasing temperature at a constant effective normal stress, the coefficient of friction of brucite decreases to a minimum of μ ≈ 0.20 near 300°C, and μ ≈ 0.22–0.24 in th
Authors
Diane E. Moore, David A. Lockner, K. Iwata, H. Tanaka, J. D. Byerlee
Science and Products
Filter Total Items: 13
No Result Found
Filter Total Items: 112
Fracture in Westerly granite under AE feedback and constant strain rate loading: Nucleation, quasi-static propagation, and the transition to unstable fracture propagation
New observations of fracture nucleation are presented from three triaxial compression experiments on intact samples of Westerly granite, using Acoustic Emission (AE) monitoring. By conducting the tests under different loading conditions, the fracture process is demonstrated for quasi-static fracture (under AE Feedback load), a slowly developing unstable fracture (loaded at a 'slow' constant strain
Authors
B.D. Thompson, R.P. Young, D. A. Lockner
Mineralogical characterization of protolith and fault rocks from the SAFOD Main Hole
Washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the San Andreas Fault Observatory at Depth (SAFOD). Both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology, P-T conditions, deformation mechanisms, and fluid composition and abundance. Regions of distinct neominerali
Authors
J.G. Solum, S.H. Hickman, D. A. Lockner, Diane E. Moore, B.A. van der Pluijm, A.M. Schleicher, J.P. Evans
Frictional strength of cuttings and core from SAFOD drillhole phases 1 and 2
We investigated the frictional properties of drill cuttings and core obtained from 1.85-3.1 km true vertical depth in the SAFOD scientific borehole in central California. Triaxial frictional sliding experiments were conducted on samples from primary lithologic traits and significant shear zones, including the inferred active trace of the San Andreas fault. The samples were deformed at room tempera
Authors
S. Tembe, D. A. Lockner, J.G. Solum, C.A. Morrow, T.-F. Wong, Diane E. Moore
Observations of premonitory acoustic emission and slip nucleation during a stick slip experiment in smooth faulted Westerly granite
To investigate laboratory earthquakes, stick-slip events were induced on a saw-cut Westerly granite sample by triaxial loading at 150 MPa confining pressure. Acoustic emissions (AE) were monitored using an innovative continuous waveform recorder. The first motion of each stick slip was recorded as a large-amplitude AE signal. These events source locate onto the saw-cut fault plane, implying that t
Authors
B.D. Thompson, R.P. Young, D. A. Lockner
High-pressure rock-physics laboratories investigate earthquake processes
No abstract available.
Authors
C.A. Morrow, D. A. Lockner
The coefficient of friction of chrysotile gouge at seismogenic depths
We report new strength data for the serpentine mineral chrysotile at effective normal stresses, σn between 40 and 200 MPa in the temperature range 25°-280°C. Overall, the coefficient of friction, μ (= shear stress/effective normal stress) of water-saturated chrysotile gouge increases both with increasing temperature and σn, but the rates vary and the temperature-related increases begin at ~100°C.
Authors
Diane E. Moore, D. A. Lockner, H. Tanaka, K. Iwata
Crystallographic controls on the frictional behavior of dry and water-saturated sheet structure minerals
We compare the frictional strengths of 17 sheet structure mineral powders, measured under dry and water-saturated conditions, to identify the factors that cause many of them to be relatively weak. The dry coefficient of friction μ ranges upward from 0.2 for graphite, leveling off at 0.8 for margarite, clintonite, gibbsite, kaolinite, and lizardite. The values of μ (dry) correlate directly with cal
Authors
Diane E. Moore, D. A. Lockner
Why earthquakes correlate weakly with the solid Earth tides: Effects of periodic stress on the rate and probability of earthquake occurrence
We provide an explanation why earthquake occurrence does not correlate well with the daily solid Earth tides. The explanation is derived from analysis of laboratory experiments in which faults are loaded to quasiperiodic failure by the combined action of a constant stressing rate, intended to simulate tectonic loading, and a small sinusoidal stress, analogous to the Earth tides. Event populations
Authors
N.M. Beeler, D. A. Lockner
Anisotropic changes in P-wave velocity and attenuation during deformation and fluid infiltration of granite
Fluid infiltration and pore fluid pressure changes are known to have a significant effect on the occurrence of earthquakes. Yet, for most damaging earthquakes, with nucleation zones below a few kilometers depth, direct measurements of fluid pressure variations are not available. Instead, pore fluid pressures are inferred primarily from seismic-wave propagation characteristics such as Vp/Vs ratio,
Authors
S. A. Stanchits, D. A. Lockner, A.V. Ponomarev
32 - Rock failure and earthquakes
This chapter summarizes experimental observations and related theoretical developments of faulted and intact rock properties related to earthquake nucleation, failure and dynamic slip. We will be concerned primarily with earthquakes occurring in the brittle crust. Intermediate and deep-focus earthquakes have unique mechanical considerations that are discussed in Section 7. We focus on repeatable l
Authors
David A. Lockner, Nicholas M. Beeler
Undrained poroelastic response of sandstones to deviatoric stress change
Deformation of porous crustal rock through diagenesis, tectonic loading, or other processes can change pore volume and affect fluid pressure. The largest stress-induced pore pressure changes occur when fluid is trapped in pores in an “undrained” condition. We have measured the undrained poroelastic response of two sandstones to changes in mean and deviatoric stress. Pore pressure was found to resp
Authors
D. A. Lockner, S. A. Stanchits
How brucite may affect the frictional properties of serpentinite
The frictional strength of brucite gouge has been measured at hydrothermal conditions to 450°C. At room temperature, brucite has a coefficient of friction, μ ≈ 0.30, making it one of the weakest minerals identified to date. With increasing temperature at a constant effective normal stress, the coefficient of friction of brucite decreases to a minimum of μ ≈ 0.20 near 300°C, and μ ≈ 0.22–0.24 in th
Authors
Diane E. Moore, David A. Lockner, K. Iwata, H. Tanaka, J. D. Byerlee