Nonplanar Faults: Mechanics of Slip and Off-fault Damage

Dieterich, James H.; Smith, D. E.

doi:10.1007/s00024-009-0517-y

Cited by 126 publications

(141 citation statements)

References 35 publications

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“…Self-affinity, or non-uniform scaling in shape and spatial trajectory along a geometric profile (Addison, 1997), has also been observed on natural faults and fractures over more than twelve orders of magnitude (Power et al, 1987;Power et al, 1988;Power and Tullis, 1991;Candela et al, 2011b;Renard et al, 2013). The geometry of fractal faults can be parameterized using the Hurst exponent, H, and an amplitude factor, β (e.g., Dieterich and Smith, 2009). These represent the degree of selfaffinity of the fault profile and the root mean square (rms) slope of fault elements, respectively.…”

Section: Fractal Descriptions Of 2d Fault Roughnessmentioning

confidence: 96%

“…1. Dieterich and Smith (2009) assert that H = 0.5-1.0 for natural fault surfaces, and that β = 0.02-0.10 for faults on the order of L ≥ 1 km. Candela et al (2009) suggest that values of β and H can be used to characterize the amount of mechanical wear of a fault surface at various scales, with these fractal parameters used to describe the level to which asperities have been worn down and removed from a fault surface.…”

Section: Fractal Descriptions Of 2d Fault Roughnessmentioning

confidence: 99%

“…Fault roughness has also been shown to have an appreciable effect on patterns of seismicity on faults of many scales (Candela et al, 2011a;Powers and Jordan, 2010). In addition to causing stress heterogeneity around faults (Chester and Chester, 2000;Nielsen and Knopoff, 1998;Saucier et al, 1992), fault roughness has been demonstrated to impede slip on faults (Dieterich and Smith, 2009;Fang and Dunham, 2013;Nielsen and Knopoff, 1998). Together, such heterogeneity in slip, slip rate, and normal stress may lead to heterogeneous frictional weakening processes during slip events, including fault opening (Griffith et al, 2010).…”

Section: Introductionmentioning

confidence: 95%

See 2 more Smart Citations

The work budget of rough faults

Newman

Griffith

2014

Tectonophysics

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Section: Fractal Descriptions Of 2d Fault Roughnessmentioning

confidence: 96%

Section: Fractal Descriptions Of 2d Fault Roughnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

The work budget of rough faults

Newman

Griffith

2014

Tectonophysics

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“…A similar resistance arises during the sliding of glaciers and ice sheets over rough beds [Nye, 1969[Nye, , 1970. Dieterich and Smith [2009] were the first to recognize the importance of this effect for faulting; they called it the back stress, though in this study we adopt the more specific term "roughness drag," denoted as drag . Using a two-dimensional static, linear elastic boundary element model with constant friction coefficient, Dieterich and Smith [2009] found that roughness reduces fault slip below that occurring on planar faults.…”

Section: Effects Of Roughness On Fault Mechanicsmentioning

confidence: 99%

“…Dieterich and Smith [2009] were the first to recognize the importance of this effect for faulting; they called it the back stress, though in this study we adopt the more specific term "roughness drag," denoted as drag . Using a two-dimensional static, linear elastic boundary element model with constant friction coefficient, Dieterich and Smith [2009] found that roughness reduces fault slip below that occurring on planar faults. They proposed that the otherwise ever-growing roughnessinduced stress perturbations are instead relaxed via brittle failure processes (off-fault seismicity and secondary faulting) within the off-fault material.…”

Section: Effects Of Roughness On Fault Mechanicsmentioning

confidence: 99%

Additional shear resistance from fault roughness and stress levels on geometrically complex faults

2013

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[1] The majority of crustal faults host earthquakes when the ratio of average background shear stress b to effective normal stress eff is b / eff 0.6. In contrast, mature plate-boundary faults like the San Andreas Fault (SAF) operate at b / eff 0.2. Dynamic weakening, the dramatic reduction in frictional resistance at coseismic slip velocities that is commonly observed in laboratory experiments, provides a leading explanation for low stress levels on mature faults. Strongly velocity-weakening friction laws permit rupture propagation on flat faults above a critical stress level pulse / eff 0.25. Provided that dynamic weakening is not restricted to mature faults, the higher stress levels on most faults are puzzling. In this work, we present a self-consistent explanation for the relatively high stress levels on immature faults that is compatible with low coseismic frictional resistance, from dynamic weakening, for all faults. We appeal to differences in structural complexity with the premise that geometric irregularities introduce resistance to slip in addition to frictional resistance. This general idea is quantified for the special case of self-similar fractal roughness of the fault surface. Natural faults have roughness characterized by amplitude-to-wavelength ratios˛between 10 -3 and 10 -2 . Through a second-order boundary perturbation analysis of quasi-static frictionless sliding across a band-limited self-similar interface in an ideally elastic solid, we demonstrate that roughness induces an additional shear resistance to slip, or roughness drag, given by drag = 8 3˛2 G * / min , for G * = G/(1 -) with shear modulus G and Poisson's ratio , slip , and minimum roughness wavelength min . The influence of roughness drag on fault mechanics is verified through an extensive set of dynamic rupture simulations of earthquakes on strongly rate-weakening fractal faults with elastic-plastic off-fault response. The simulations suggest that fault rupture, in the form of self-healing slip pulses, becomes probable above a background stress level b pulse + drag . For the smoothest faults (˛ 10 -3 ), drag is negligible compared to frictional resistance, so that b pulse 0.25 eff . However, on rougher faults (˛ 10 -2 ), roughness drag can exceed frictional resistance. We expect that drag ultimately departs from the predicted scaling when roughness-induced stress perturbations activate pervasive off-fault inelastic deformation, such that background stress saturates at a limit ( b 0.6 eff ) determined by the finite strength of the off-fault material. We speculate that this strength, and not the much smaller dynamically weakened frictional strength, determines the stress levels at which the majority of faults operate.Citation: Fang, Z., and E. M. Dunham (2013), Additional shear resistance from fault roughness and stress levels on geometrically complex faults,

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Off-fault long-term damage: A condition to account for generic, triangular earthquake slip profiles

Cappa

Perrin

Manighetti

et al. 2014

Geochem. Geophys. Geosyst.

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Natural earthquake slip profiles have a generic triangular shape which the available rupture dynamics models fail to reproduce. Long-term faults are embedded in long-damaged crustal material, and the properties of the long-term damage vary both across and along the faults. We examine the effects of the predamaged state of the medium on the earthquake slip distributions. We simulate long-term damage by the decrease in the elastic modulus of the medium around the fault. We model the dynamic crack-like rupture of a slip-weakening planar, right-lateral strike-slip fault, and search which geometries and elastic properties of the long-term damage produce a triangular slip profile on the rupture. We find that such a profile is produced only when a laterally heterogeneous preexisting damage zone surrounds the ruptured fault. The highest on-fault slip develops in the most compliant region of the damage zone, and not necessarily above the earthquake hypocenter. The coseismic slip decreases in zones of stiffer damage. The amount of coseismic slip dissipated in the damage zone is large, at least 25-40% of maximum on-fault slip, and can occur over large distances from the fault. Our study thus emphasizes that off-fault preexisting damage should be considered for an accurate description of earthquake ruptures. It also motivates a reformulation of the available earthquake source inversion models since most of them do not include the inelastic deformations that occur in the near field of the earthquake ruptures.

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Nonplanar Faults: Mechanics of Slip and Off-fault Damage

Cited by 126 publications

References 35 publications

The work budget of rough faults

The work budget of rough faults

Additional shear resistance from fault roughness and stress levels on geometrically complex faults

Off-fault long-term damage: A condition to account for generic, triangular earthquake slip profiles

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