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J.D. Byerlee

Publications and source records attributed to J.D. Byerlee.

At least 19 recordsLinked to original sources
USGS2012

Fault stability inferred from granite sliding experiments at hydrothermal conditions

Seismicity on crustal faults is concentrated in the depth interval 1–3 to 12–15km. Tse and Rice (1986) suggested that the lower bound on seismicity is due to a switch with increasing temperature from velocity weakening (destabilizing) to velocity strengthening (stabilizing) friction. They inferred this transition from friction data for dry granite; however, pore fluids exist at elevated temperatures throughout the crust, and may strongly influence strength and sliding behavior. We present new data from sliding experiments on granite at elevated T (23° to 600°) plus elevated PH 2 O (100 MPa),

Geophysical Research Letters↗
USGS2012

Coulomb plasticity within the fault zone

We represent a well‐developed fault by a layer of granular material (fault gouge) confined between two competent fault blocks. Slip on such a fault involves plastic shearing of the fault gouge. That is, the fault gouge behaves as a Coulomb material, and the plastic flow is accomplished by slip on the two sets of Coulomb shears appropriate to the stress state and the frictional properties of the gouge. Neither set of Coulomb shears is coplanar with the fault zone. Generally, the initial plastic flow is self arresting, and increased shear stress is required to drive further shear. But as the shear stress is increased a stress state is reached within the gouge in which the plane of maximum shear stress is parallel to the plane of the fault zone. Then the fault gouge shears at whatever rate is required to keep the shear stress across the fault from increasing further as was demonstrated experimentally by Mandl et al. [1977]. In a mature fault previous slip cycles have presumably left the fault gouge in a stress state such that the plane of maximum shear is parallel to the fault plane. Then, with additional shear loading, unlimited shear deformation is possible at the shear stress corresponding to the onset of Coulomb failure, and the fault appears to slip as if friction on the plane of the fault were less than on planes of other orientations. Slip on the fault does not imply that the fault plane coincides with a Coulomb shear as is sometimes assumed.

Geophysical Research Letters↗
USGS2012

Permeability of fault gouge under confining pressure and shear stress

The permeability of both clay-rich and non-clay gouges, as well as several pure clays, was studied as a function of confining pressures from 5 to 200 MPa and shear strain to 10. Permeability ranged over four orders of magnitude, from around 10 −22 to 10 −18 m 2 (1 darcy = 0.987 × 10 −12 m 2 ). The lowest values were characteristic of the montmorillonite-rich and finer grained non-clay gouges. Illite, kaolinite, and chlorite had intermediate permeabilities, while the highest values were typical of the serpentine and coarser grained non-clay gouges. Grain size was an important factor in determining permeability, particularly for the clay-rich samples. The coarse grained gouges were the most permeable and decreased in permeability after shearing. Conversely, the fine grained gouges had characteristically lower permeabilities that did not vary significantly after various amounts of shearing. The permeabilities of the non-clay samples were not significantly different than those of the clays. Therefore, comminuted rock flours can be equally as effective in reducing the flow of water as the characteristically low permeability clay gouges. The strengths of the samples were quite variable. The non-clay gouges were consistently the strongest, with yield points (beginning of nonelastic behavior) around 850 MPa, while montmorillonite had an anomalously low strength in relation to all the other gouges at 250 MPa. Strength of the saturated samples under drained (low pore pressure) conditions did not correlate with high or low permeability. However, the low permeabilities of these gouges could be a factor in the measured low shear stresses along fault regions if excess pore pressures were created as a result of shearing or compaction, and this pressure was unable to dissipate through a thick section of the material.

Journal of Geophysical Research Solid Earth↗
USGS2001

Rapid fluid disruption: A source for self-potential anomalies on volcanoes

Self-potential (SP) anomalies observed above suspected magma reservoirs, dikes, etc., on various volcanoes (Kilauea, Hawaii; Mount Unzen, Japan; Piton de la Fournaise, Reunion Island, Miyake Jima, Japan) result from transient surface electric fields of tens of millivolts per kilometer and generally have a positive polarity. These SP anomalies are usually attributed to electrokinetic effects where properties controlling this process are poorly constrained. We propose an alternate explanation that contributions to electric fields of correct polarity should be expected from charge generation by fluid vaporization/disruption. As liquids are vaporized or removed as droplets by gas transport away from hot dike intrusions, both charge generation and local increase in electrical resistivity by removal of fluids should occur. We report laboratory observations of electric fields in hot rock samples generated by pulses of fluid (water) through the rock at atmospheric pressure. These indicate the relative amplitudes of rapid fluid disruption (RFD) potentials and electrokinetic potentials to be dramatically different and the signals are opposite in sign. Above vaporization temperatures, RFD effects of positive sign in the direction of gas flow dominate, whereas below these temperatures, effects of negative sign dominate. This suggests that the primary contribution to observed self-potential anomalies arises from gas-related charge transport processes at temperatures high enough to produce vigorous boiling and vapor transport. At lower temperatures, the primary contribution is from electrokinetic effects modulated perhaps by changing electrical resistivity and RFD effects from high-pressure but low-temperature CO2 and SO2 gas flow ripping water molecules from saturated crustal rocks. If charge generation is continuous, as could well occur above a newly emplaced dike, positive static potentials will be set up that could be sustained for many years, and the simplest method for identifying these hot, active regions would be to identify the SP anomalies they generate.

Hawai'i↗
USGS2001

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 the temperature range 350–450°C. Brucite has a sheeted crystal structure, and its low frictional strength may be attributed to the relatively weak bonds between the layers. In addition, the temperature dependence of μ to ≈300°C can be explained in terms of the anomalously large coefficient of thermal expansion of brucite, which will further weaken the interlayer bonds. Brucite is a common constituent of serpentinite, and at ≈300°C, where brucite is weakest, all the major serpentine minerals have μ ≥ 0.5. The maximum expected brucite content of a serpentinite is close to 20% by weight or volume. That amount of disseminated brucite will lower the coefficient of friction of serpentinite by ≤10–15% in the deeper parts of the seismogenic zone. However, the effect will be much greater if shear can be concentrated along brucite-lined slip surfaces in the serpentinite body.

Open-File Report↗
USGS1996

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 α 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 required axial stress increases at a decreasing rate to a maximum, beyond which a roughly constant axial stress is sufficient to maintain the constant rate of shortening. Such triaxial tests were run for saw cuts inclined at angles α of 20°, 25°, 30°, 35°, 40°, 45°, and 50° to the cylinder axis, and the apparent coefficient of friction μ a (ratio of the shear stress to the normal stress, both stresses resolved onto the saw cut) at failure was determined. Subject to the assumption that the observed failure involves slip on Coulomb shears (orientation unspecified), the orientation of the principal compression axis within the gouge can be calculated as a function of μ a for a given value of the coefficient of internal friction μ i . The rotation of the principal stress axes within the gouge in a triaxial test can then be followed as the shear strain across the gouge layer increases. For μ i ∼ 0.8, an appropriate value for highly sheared sand, the observed values μ a imply that the principal axis of compression within the gouge rotates so as to approach being parallel to the cylinder axis for all saw cut angles (20° < α < 50°). In the limiting state (principal compression axis parallel to cylinder axis) the stress state in the gouge layer would be the same as that in the granite cylinder, and the failure criterion would be independent of the saw cut angle.

Journal of Geophysical Research B: Solid Earth↗
USGS1996

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 frictional strength of a pure chrysotile gouge at temperatures to 290 °C and axial-shortening velocities as low as 0.001 μm/s. As temperature increases to ≈ 100 °C, the strength of the chrysotile gouge decreases slightly at low velocities, but at temperatures ≥200 °C, it is substantially stronger and essentially independent of velocity at the lowest velocities tested. We estimate that pure chrysotile gouge at hydrostatic fluid pressure and appropriate temperatures would have shear strength averaged over a depth of 14 km of 50 MPa. Thus, on the sole basis of its strength, chrysotile cannot be the cause of a weak San Andreas fault. However, chrysotile may also contribute to low fault strength by forming mineral seals that promote the development of high fluid pressures.

Geology↗
USGS1995

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 is supported by a small number of compartments where the pore pressure is relatively low. As a result, the fault gouge in these compartments is compacted and lithified and has a high undisturbed strength. When one of these locked regions fails, the system made up of the neighboring high and low pressure compartments can become unstable. Material in the high fluid pressure compartments is initially underconsolidated since the low effective confining pressure has retarded compaction. As these compartments are deformed, fluid pressure remains nearly unchanged so that they offer little resistance to shear. The low pore pressure compartments, however, are overconsolidated and dilate as they are sheared. Decompression of the pore fluid in these compartments lowers fluid pressure, increasing effective normal stress and shear strength. While this effect tends to stabilize the fault, it can be shown that this dilatancy hardening can be more than offset by displacement weakening of the fault (i.e., the drop from peak to residual strength). If the surrounding rock mass is sufficiently compliant to produce an instability, slip will propagate along the fault until the shear fracture runs into a low-stress region. Frictional heating and the accompanying increase in fluid pressure that are suggested to occur during shearing of the fault zone will act as additional destabilizers. However, significant heating occurs only after a finite amount of slip and therefore is more likely to contribute to the energetics of rupture propagation than to the initiation of the instability. We present results of a one-dimensional dynamic Burridge-Knopoff-type model to demonstrate various aspects of the fluid-assisted fault instability described above. In the numerical model, the fault is represented by a series of blocks and springs, with fault rheology expressed by static and dynamic friction. In addition, the fault surface of each block has associated with it pore pressure, porosity and permeability. All of these variables are allowed to evolve with time, resulting in a wide range of phenomena related to fluid diffusion, dilatancy, compaction and heating. These phenomena include creep events, diffusion-controlled precursors, triggered earthquakes, foreshocks, aftershocks, and multiple earthquakes. While the simulations have limitations inherent to 1-D fault models, they demonstrate that the fluid compartment model can, in principle, provide the rich assortment of phenomena that have been associated with earthquakes. ?? 1995 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗
USGS1994

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 shear failure. The failure strength is parameterized by the coefficient of internal friction ??, based on the Mohr-Coulomb failure criterion. Samples of remoulded Lopez gouge have internal friction ??=0.6??0.02. In experiments where the ends of the sample are constrained to remain axially aligned, suppressing strain localisation, the sample compacts before failure and dilates persistently after failure. In experiments where one end of the sample is free to move laterally, the strain localises to a single oblique fault at around the point of failure; some dilation occurs but does not persist. A comparison of these experiments suggests that dilation is confined to the region of shear localisation in a sample. Overconsolidated samples have slightly larger failure strengths than normally consolidated samples, and smaller axial strains are required to cause failure. A large amount of dilation occurs after failure in heavily overconsolidated samples, suggesting that dilation is occurring throughout the sample. Undisturbed samples of Lopez gouge, cored from the outcrop, have internal friction in the range ??=0.4-0.6; the upper end of this range corresponds to the value established for remoulded Lopez gouge. Some kind of natural heterogeneity within the undisturbed samples is probably responsible for their low, variable strength. In samples of simulated gouge, with a more uniform grain size, active cataclasis during axial loading leads to large amounts of compaction. Larger axial strains are required to cause failure in simulated gouge, but the failure strength is similar to that of natural Lopez gouge. Use of the Mohr-Coulomb failure criterion to interpret the results from this study, and other recent studies on intact rock and granular gouge, leads to values of ?? that depend on the loading configuration and the intact or granular state of the sample. Conceptual models are advanced to account for these descrepancies. The consequences for strain-weakening of natural faults are also discussed. ?? 1994 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗
USGS1994

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 eventually drops to the level of intact granite. These results support the fault-valve model for the development of mesothermal ore deposits, in which seals are formed at the base of the seismogenic zone of high-angle thrust faults. The lower temperature results yield varying estimates of mineral-sealing rates at shallower depths in fault zones, although they generally support the hypothesis that such seals develop in less time than the recurrence interval for moderate to large earthquakes on the San Andreas fault.

California↗
USGS1993

How geometrical constraints contribute to the weakness of mature faults

Increasing evidence that the San Andreas fault has low shear strength 1 has fuelled considerable discussion regarding the role of fluid pressure in controlling fault strength. Byerlee 2,3 and Rice 4 have shown how fluid pressure gradients within a fault zone can produce a fault with low strength while avoiding hydraulic fracture of the surrounding rock due to excessive fluid pressure. It may not be widely realised, however, that the same analysis 2–4 shows that even in the absence of fluids, the presence of a relatively soft 'gouge' layer surrounded by harder country rock can also reduce the effective shear strength of the fault. As shown most recently by Byerlee and Savage 5 , as the shear stress across a fault increases, the stress state within the fault zone evolves to a limiting condition in which the maximum shear stress within the fault zone is parallel to the fault, which then slips with a lower apparent coefficient of friction than the same material unconstrained by the fault. Here we confirm the importance of fault geometry in determining the apparent weakness of fault zones, by showing that the apparent friction on a sawcut granite surface can be predicted from the friction measured in intact rock, given only the geometrical constraints introduced by the fault surfaces. This link between the sliding friction of faults and the internal friction of intact rock suggests a new approach to understanding the microphysical processes that underlie friction in brittle materials.

Nature↗
USGS1992

Observations of quasistatic fault growth from acoustic emissions

The location of acoustic emission (AE) sources during deformation of rock has proven to be a useful non-destructive analytic technique. We present experimental results,based on AE observations, that show the nucleation and growth of macroscopic fault planes in granite and sandstone samples. By controlling axial stress to maintain constant AE rate rather than more conventional loading conditions such as constant strain rate or constant stress, we have been successful in retarding the failure process in triaxial experiments. As a result, the post-failure stress curve has been followed quasistatically, extending to minutes or hours the fault growth process that normally would occur violently in a fraction of a second. In addition to this novel control system, three-dimensional locations of AE events were determined by analyzing the relative arrival times of AE pulses recorded on a network of transducers attached to the sample. In this manner, as many as 40 000 AE events were located in the course of a single experiment. While the details of fault formation varied from experiment to experiment, a number of features were consistently observed. In all three granite experiments, the fault plane nucleated abruptly at a point on the sample surface soon after reaching peak stress. Prior to fault nucleation, microcrack growth was distributed evenly throughout the granite samples. From the nucleation site, the fault plane grew across the sample, accompanied by a gradual drop in axial stress. AE locations showed that the fault propagated as a fracture front (process zone) with in-plane dimension of 10-50 mm. As the fracture front passed, the AE from a given region would drop to a low level. If allowed to progress to completion, stress eventually dropped to the frictional sliding strength. Sandstone samples showed somewhat different response. In these experiments, a diffuse damage zone appeared prior to peak strength and gradually localized into an incipient fault plane. After passing through peak stress, this plane grew, as in the granite samples, to eventually bisect the sample.

International Geophysics↗
USGS1992

An earthquake mechanism based on rapid sealing of faults

Recent seismological, heat flow and stress measurements in active fault zones such as the San Andreas have led to the suggestion 1,2 that such zones can be relatively weak. One explanation for this may be the presence of overpressured fluids along the fault 3–5 , which would reduce the shear stress required for sliding by partially 'floating' the rock. Although several mechanisms have been proposed for overpressurizing fault fluids 3,4,6,7 , we recall that 'pressure seals' are known to form in both sedimentary 8 and igneous 9 rocks by the redistribution of materials in solution; the formation of such a seal along the boundaries of a fault will prevent the communication of fluids between the porous, deforming fault zone and the surrounding country rock. Compaction of fault gouge, under hydrostatic loading and/or during shear, elevates pore pressure in the sealed fault and allows sliding at low shear stress. We report the results of laboratory sliding experiments on granite, which demonstrate that the sliding resistance of faults can be significantly decreased by sealing and compaction. The weakening that results from shear-induced compaction can be rapid, and may provide an instability mechanism for earthquakes.

Nature↗
USGS1991

Quasi-static fault growth and shear fracture energy in granite

The failure process in a brittle granite sample can be stabilized by controlling axial stress to maintain a constant rate of acoustic emission. As a result, the post-failure stress curve can be followed quasistatically, extending to hours the fault growth process which normally would occur violently in a fraction of a second. Using a procedure originally developed to locate earthquakes, acoustic emission arrival-time data are inverted to obtain three-dimensional locations of microseisms. These locations provide a detailed view of fracture nucleation and growth.

Nature↗
USGS1991

Comparative geometry of the San Andreas Fault, California, and laboratory fault zones

Textural examination of fault gouge deformed in triaxial friction experiments has revealed differences in the orientations of secondary shear sets between the stably sliding and stick-slip samples. In order to determine whether such differences can be identified in natural faults, maps of recently active breaks along the San Andreas fault from Point Arena to Cajon Pass, California, were examined to compare the types and orientations of secondary structures mapped in the creeping and locked sections. The fault zone was divided into 52 geometrically defined segments of uniform strike, which were then grouped into 7 sections: 4 straight and 2 curved sections, and Cholame Valley. One of the straight sections is the creeping section between San Juan Bautista and Cholame in central California; the rest of the sections are locked. Many of the gross geometric characteristics of the individual segments, such as length, width, and stepover size, reflect their position in either a straight or a curved section. In contrast, with respect to the orientations of the recent breaks within the segments, the single creeping section differs from all of the locked sections, both straight and curved, as follows: (1) the traces of recent breaks with a more west-ward orientation than the local strike of the fault zone (P traces) dominate over those with a more northward orientation (R traces) in the creeping section, whereas the opposite relationship holds in the locked sections, and (2) the more northward-oriented (R) traces make larger angles to the local strike of the fault zone in the locked sections than in the creeping section. The latter result is consistent with the orientations of R shears in our various laboratory samples. The former result was unexpected, because of the predominance of R shears in most laboratory samples, but a small number of samples are analogous to the creeping section in terms of their P-shear abundances, R-shear orientations, and sliding behavior. The causes of these distinguishing characteristics are not yet understood.

California↗
USGS1991

A note on the frictional strength of laumontite from Cajon Pass, California

Laumontite mineralization is pervasive in joints and shear zones encountered in the Cajon Pass drillhole in southern California. In order to determine whether a gouge composed of this hydrated mineral affects shear strength in a manner similar to low-strength, clay-rich fault gouges, frictional sliding experiments were performed under dry, saturated and high pore pressure conditions at effective pressures up to 450 MPa. Coefficients of friction ranged between 0.66 and 0.84, consistent with most crustal rocks and well above the values typical of clay-rich San Andreas fault gouges. Saturation state had no effect on strength or sliding stability. These results suggest that the presence of laumontite in shear zones at Cajon Pass will not affect the shear strength of the rock in a way that can account for the inferred low ambient shear stresses. -Authors

Geophysical Research Letters↗