Dilatancy of quartz gouge in pure shear

Raleigh, Barry; Marone, Chris

doi:10.1029/gm036p0001

Cited by 9 publications

(2 citation statements)

References 19 publications

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“…In experiments [e.g., Teufel, 1981;Raleigh and Marone, 1986;Marone et al, 1990] the slip on a frictional surface is often accompanied by a plastic dilatancy inside the sheared zone. Although the existence and magnitude of this behavior in field processes is largely an unresolved issue, several analyses [Rudnicki and Chen, 1988;Segall and Rice, 1995] have shown that this dilatancy has a strong influence on the stability of the slip.…”

Section: Plastic Porosity Changesmentioning

confidence: 99%

Effects of normal stress variations on frictional stability of a fluid‐infiltrated fault

Chambon

Rudnicki²

2001

J. Geophys. Res.

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Abstract. This paper extends the spring-slider model of Segall and Rice [ 1995] for dilating fluid-infiltrated faults to include geometry-induced normal stress variations. Because of the coupling between normal and shear stresses on a dipping plane the shear stress drop accompanying slip is associated with a decrease in normal stress for reverse faulting and with an increase for normal faulting. This coupling stabilizes frictional sliding on normal faults and destabilizes it on reverse faults. When a fluid phase is present, these normal stress variations during slip events also trigger, through poroelastic coupling, compensating pore pressure changes: stabilizing pressure decreases for reverse geometry and destabilizing increases for normal geometry. Fault stability is quantitatively studied using two parameters: the critical spring stiffness kcr separating the stable and unstable slip domains and, when numerical simulations exhibit stick-slip cycles, the stress drop during the slip phases At. As expected, geometric coupling is found to reduce kcr and Ar for normal faults (in comparison with Segal! and Rice's [1995] strike-slip geometry) and to increase these parameters for reverse faults. Poroelastic coupling shows opposite consequences. The combined effect of shear-induced dilatancy and poroelastic coupling is stabilizing for reverse geometry but can be either stabilizing or destabilizing for normal geometry, depending on the dilatancy magnitude. Nevertheless, the stability differences between the types of faults are primarily controlled by the geometric coupling between shear and normal stresses: For all the parameters we investigated, normal faults exhibit lower stress drops (and critical stiffnesses) than reverse faults. Finally, extrema appearing in the graphs featuring A r or kcr versus the diffusion rate demonstrate that the influence of the fluid effects is not maximum in the undrained case. Surprisingly, their influence is maximum at a point intermediate between the drained and undrained limits, when the diffusion time is roughly equal to the frictional relaxation time associated with stick phases. This phenomenon is presumably caused by subtle second-order mechanisms involving the instantaneous pore pressure changes induced by the poroelastic coupling in response to instantaneous friction changes and the interseismic pressure recovery process.

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Section: Plastic Porosity Changesmentioning

confidence: 99%

Effects of normal stress variations on frictional stability of a fluid‐infiltrated fault

Chambon

Rudnicki²

2001

J. Geophys. Res.

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“…Chinnery (1966a,b) also considered strikeslip movements in regions of pure shear and extension. Rayleigh & Marone (1986) suggested that, 'ideally', strike-slip faults are driven to failure by pure shear loading. Bombolakis (1976, fig.…”

Section: Introductionmentioning

confidence: 99%

Fracture mechanics model of a fault termination zone

Rabinovitch

Friedman²,

Bahat

2011

Geol. Mag.

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A fault termination zone from Middle Eocene chalks near Beer Sheva, Israel, is analysed via a fracture mechanical technique. The zone consists of the end of the primary fault, three secondary faults and joints associated with these structures. We demonstrate that the shape of the first secondary fault can be obtained from theoretical fracture mechanical calculations. This shape also enables us to obtain the set of conditions which induced the observed structures. The technique reveals the relative importance of the different variables that appear in the theory. The most significant parameters in determining the shape of the first secondary fault are the vertical dimension of the primary fault, the ratio of the two horizontal differential stresses and the initiation angle of the secondary fault. Results indicate that the fault termination zone was created under an almost pure shear load. The true lateral displacement of the primary fault is unknown; hence, exact calculation of the stresses leading to the secondary fault is hardly possible. However, an estimation, based on a partial conversion of this displacement to an uplift, yields σ1 and σ3 values at initiation of between 3.8 and 7.6 MPa and 3.65 and 7.3 MPa, respectively.

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Deformation of Earth Materials: Six Easy Pieces

Evans

Dresen

1991

Reviews of Geophysics

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Detailed knowledge of rheology is critical to understanding tectonic processes. Laboratory experiments to determine the strength of rocks have provided quantitative bounds on the strength of the crust and mantle. This knowledge has allowed computation of large scale deformation in the asthenosphere, given guidance in interpreting field structures, and improved our knowledge of the earthquake process. Progress has been particularly rapid in some areas: the effect of point defect chemistry on high temperature strength; the effect of water on rock strength, recrystallization and grain boundary processes; deformation processes in two‐phase materials; the application of linear elastic fracture mechanics; and the physics of rock friction and instability. Further progress requires increased knowledge of the effect of fluids and fluid flow on strength; of the ways in which chemical reactions and deformation interact, and of the physics and kinetics of deformation mechanisms

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Dilatancy of quartz gouge in pure shear

Abstract: Dilatancy in artificial fault gouge consisting of quartz sand is produced under pure shear loading conditions at shear stresses of about 1/2 the frictional shear failure strength.

Cited by 9 publications

References 19 publications

Effects of normal stress variations on frictional stability of a fluid‐infiltrated fault

Effects of normal stress variations on frictional stability of a fluid‐infiltrated fault

Fracture mechanics model of a fault termination zone

Deformation of Earth Materials: Six Easy Pieces

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