Journal ArticleDOI
Scaling of Rock Friction Constitutive Parameters: The Effects of Surface Roughness and Cumulative Offset on Friction of Gabbro
Chris Marone,Simon Cox +1 more
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In this paper, the authors describe experiments in which large blocks of gabbro were sheared in a direct shear apparatus at room temperature, 5 MPa normal stress, and slip velocities from 0.1 to 10 μm/s.Abstract:
We describe experiments in which large (14×40 cm nominal contact area) blocks of gabbro were sheared in a direct shear apparatus at room temperature, 5 MPa normal stress, and slip velocities from 0.1 to 10 μm/s. The apparatus was servocontrolled using a displacement feedback measurement made directly between the gabbro blocks. Two surface roughnesses were studied (rough, produced by sandblasting, and smooth, produced by lapping with #60 grit) and accumulated displacements reached 60 mm. Measurements of surface topography were used to characterize roughness and asperity dimensions. Step changes in loading velocity were used to interrogate friction constitutive properties. Both rough and smooth surfaces showed appreciable displacement hardening. The coefficient of friction μ for rough surfaces was about 0.45 for initial slip and 0.7 after sliding 50 mm. Smooth surfaces exhibited higher μ and a greater tendency for unstable slip. The velocity dependence of frictiona−b and the characteristic friction distanceD
c
show systematic variations with accumulated displacement. For rough surfacesa−b started out positive and became negative after about 50 mm displacement andD
c
increased from 1 to 4 μm over the same interval. For smooth surfaces,a−b began negative and decreased slightly with displacement andD
c
was about 2 μm, independent of displacement. For displacements <30 mm, rough surfaces exhibit a second state variable with characteristic distance about 20 μm. The decrease ina−b with displacement is associated with disappearance of the second state variable. Our data indicate thatD
c
is controlled by surface roughness in a complex way, including but not limited to the effect of roughness on contact junction dimensions for bare rock surfaces. The data show that simple descriptions of roughness, such as rms and peak-to-trough, are not sufficient to inferD
c
. Our observations are consistent with a model in whichD
c
scales with gouge thickness.read more
Citations
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Journal ArticleDOI
Laboratory-derived friction laws and their application to seismic faulting
TL;DR: In this article, a review of the relationship between friction and the properties of earthquake faults is presented, as well as an interpretation of the friction state variable, including its interpretation as a measure of average asperity contact time and porosity within granular fault gouge.
Journal ArticleDOI
Frictional and hydrologic properties of clay‐rich fault gouge
TL;DR: In this paper, the authors measured the strength, friction constitutive properties, and permeability of a suite of saturated clay-rich fault gouges, including: a 50:50% mixture of montmorillonite-quartz, powdered illite shale, and powdered chlorite schist.
Journal ArticleDOI
Friction of simulated fault gouge for a wide range of velocities and normal stresses
Karen Mair,Chris Marone +1 more
TL;DR: In this paper, the authors studied the friction of simulated fault gouge as a function of normal stress (σn = 25 to 70 MPa) and load point velocity (V = 0.001 to 10 mm/s).
Journal ArticleDOI
Constitutive relationships and physical basis of fault strength due to flash heating
TL;DR: In this article, the authors developed a model of fault strength loss resulting from phase change at asperity contacts due to flash heating that considers a distribution of contact sizes and nonsteady state evolution of the fault strength with displacement, and predicted slip speed for the onset of weakening is in the range of 0.05 to 2 m/s.
Journal ArticleDOI
Preslip and cascade processes initiating laboratory stick slip
TL;DR: In this article, the authors used a high dynamic range recording system to directly compare the seismic waves radiated during the stick-slip event to those radiated from tiny (M −6) discrete seismic events, commonly known as acoustic emissions (AEs), that occur in the seconds prior to each large stick slip.
References
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Book
The Mechanics of Earthquakes and Faulting
TL;DR: The connection between faults and the seismicity generated is governed by the rate and state dependent friction laws -producing distinctive seismic styles of faulting and a gamut of earthquake phenomena including aftershocks, afterslip, earthquake triggering, and slow slip events.
Journal ArticleDOI
Slip instability and state variable friction laws
TL;DR: In this paper, the dependence of the friction force on slip history is described by an experimentally motivated constitutive law where the friction forces are dependent on slip rate and state variables.
Journal ArticleDOI
Modeling of rock friction: 1. Experimental results and constitutive equations
TL;DR: In this paper, it is shown that the strength of the population of points of contacts between sliding surfaces determines frictional strength and that the number of contacts changes continuously with displacements.
Journal ArticleDOI
Spatio-temporal complexity of slip on a fault
TL;DR: In this article, a three-dimensional analysis of slip on a long vertical strike-slip fault between steadily driven elastic crustal blocks is presented, where the dynamics of the system are taken either as uniform along-strike at every depth or as perturbed modestly from uniformity.
Journal ArticleDOI
Stability of Steady Frictional Slipping
James R. Rice,Andy Ruina +1 more
TL;DR: In this article, the authors established linear stability conditions for slip surfaces at fixed normal stress, where the shear resistance of slipping surfaces is given by r = r( v,state) /iJV>O.