Growth of molten zone as a mechanism of slip weakening of simulated faults in gabbro during frictional melting

Hirose, Takehiro; Shimamoto, Toshihiko

doi:10.1029/2004jb003207

Cited by 339 publications

(523 citation statements)

References 35 publications

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“…It should be noted that Eq. 2 is identical to the definitions made by Hirose and Shimamoto (2005) and Mizoguchi et al (2007). Since we used solid cylindrical specimens without hollows, we set the inner radius of the specimen to zero in their formulation.…”

Section: High-velocity Rotary Shear Apparatusmentioning

confidence: 99%

Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate

Fukuyama

Mizoguchi

2009

Int J Fract

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To reproduce the dynamic rupture process of earthquakes, the fault geometry, initial stress distribution and a frictional constitutive law on the fault are important parameters as initial and boundary conditions of the system. Here, we focus on the frictional constitutive relation on the fault. During a high-speed rupture, fault strength decreases as slip develops which can be described by a slip weakening equation. To understand the physical process of stress breakdown during the dynamic rupture of earthquakes, we investigated the friction behavior of rocks in the laboratory by direct measurements of traction evolution with slip in response to a given slip history. We employed a highspeed rotary shear apparatus introduced at National Research Institute for Earth Science and Disaster Prevention (NIED). This apparatus has a capability of sliding with predefined variable velocities using a servo-controlled system. We used a pair of granite cylindrical specimens with a diameter of 25 mm. As an input signal, we used a regularized Yoffe function to investigate the scale dependence of fracture energy and slip weakening distance (D c ). We observed a positive correlation between D c and total slip, keeping the maximum slip velocity constant. These conditions correspond to those for earthquakes with the same stress drop and varying magnitudes. Finally, we used a

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Section: High-velocity Rotary Shear Apparatusmentioning

confidence: 99%

Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate

Fukuyama

Mizoguchi

2009

Int J Fract

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“…[3] Melting of crystalline rocks such as gabbro and tonalite has been studied in several high-velocity (order of m/s) rock-friction experiments (HVRFE) [Tsutsumi and Shimamoto, 1997;Hirose and Shimamoto, 2005;Di Toro et al, 2006a, 2006b]. These experimental data show a complex evolution of shear stresses prior to and after the onset of melting, and explained by coupled thermal-fluidmechanical models [Fialko and Khazan, 2005;Sirono et al, 2006;Nielsen et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of frictional melting of argillite at high slip rates: Implications for seismic slip in subduction‐accretion complexes

et al. 2009

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[1] Discovery of pseudotachylytes from exhumed accretionary complexes indicates that frictional melting occurred along illite-rich, argillite-derived slip zones during subduction earthquakes. We conducted high-velocity friction experiments on argillite at a slip rate of 1.13 m/s and normal stresses of 2.67-13.33 MPa. Experiments show slip weakening followed by slip strengthening. Slip weakening is associated with the formation and shearing of low-viscosity melt patches. The subsequent slip strengthening occurred despite the reduction in shear strain rate due to the growth (thickening) of melt layer, suggesting that the viscosity of melt layer increased with slip. Microstructural and chemical analyses suggest that the viscosity increase during the slip strengthening is not due to an increase in the volume fraction of solid grains and bubbles in the melt layer but could be caused primarily by dehydration of the melt layer. Our experimental results suggest that viscous braking can be efficient at shallow depths of subduction-accretion complexes if substantial melt dehydration occurs on a timescale of seismic slip. Melt lubrication can possibly occur at greater depths within subduction-accretion complexes because the ratio of viscous shear to normal stress decreases with depth. Argillite-derived natural pseudotachylytes formed at seismogenic depths in subduction-accretion complexes are more hydrous than the experimentally generated pseudotachylytes and may be evidence of nearly complete stress drop.

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“…[5] Extreme dynamic weakening at coseismic slip rates has been widely observed in high-velocity friction experiments [e.g., Tsutsumi and Shimamotom, 1997;Di Toro et al, 2004;Hirose and Shimamoto, 2005;Beeler et al, 2008;Goldsby and Tullis, 2011;Di Toro et al, 2011]. Planar faults governed by strongly rate-weakening friction laws support self-sustaining slip-pulse ruptures at background stress levels b around a critical stress level pulse 0.25 eff [Cochard and Madariaga, 1996;Beeler and Tullis, 1996;Zheng and Rice, 1998;Lapusta and Rice, 2003;Lykotrafitis et al, 2006;Noda et al, 2009], even with off-fault plasticity [Dunham et al, 2011a;Gabriel et al, 2013].…”

Section: Introductionmentioning

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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Growth of molten zone as a mechanism of slip weakening of simulated faults in gabbro during frictional melting

Cited by 339 publications

References 35 publications

Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate

Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate

Experimental investigation of frictional melting of argillite at high slip rates: Implications for seismic slip in subduction‐accretion complexes

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

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