An empirically based steady state friction law and implications for fault stability

Spagnuolo, Elena; Nielsen, S. B.; Violay, Marie; Toro, Giulio Di

doi:10.1002/2016gl067881

Cited by 40 publications

(36 citation statements)

References 62 publications

(95 reference statements)

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“…Frictional weakening with increasing slip velocity is observed in fast sliding experiments of rocks (Di Toro et al, ; Spagnuolo et al, ; Wang et al, ; Yao et al, ) and invoked to explain key features of earthquake and landslide (Di Toro et al, ; Lucas et al, ). Our results show that the apparent friction coefficient drops from 0.56 to 0.34 as velocity increases to 19.7 m/s during the first accelerating cycle, and then remains at 0.3~0.34 with velocity continuously increasing during the second accelerating cycle (Figure e).…”

Section: Discussionmentioning

confidence: 99%

“…The apparent friction coefficient is considered as the effects of both true friction coefficient ( μ ′ ) and basal fluid pressure ( P ; Iverson, ):

μ σ_{n} = μ^{'} ((), σ_{n} - P)

where σ n is the normal stress at the base of the sliding mass. Based on this hypothesis, considering true friction coefficients of different rock categories are greater than 0.6 (e.g., Byerlee, ; Di Toro et al, ; Spagnuolo et al, ), this low apparent friction coefficient suggests that basal fluid pressures were at least 43% of basal normal stress. During two months before the Xinmo landslide occurred, the antecedent rainfall in Diexi town reaches 200 mm, which is 42% more than the same periods in previous years (Fan, Xu, et al, ; Wang et al, ).…”

Section: Discussionmentioning

confidence: 99%

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Chain‐Style Landslide Hazardous Process: Constraints From Seismic Signals Analysis of the 2017 Xinmo Landslide, SW China

Chen

et al. 2019

JGR Solid Earth

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Landslides generally involve rapid acceleration and deceleration of huge mass in just several minutes, and their unpredictability have made real‐time detections of their rapid processes difficult. Seismic signals generated by landslides provide an excellent opportunity to obtain the time‐dependent observations on landslide's processes. We invert the force‐time function by fitting long‐period seismic signals generated by Xinmo landslide on 23 June 2017, SW China, and determine three‐stage dynamic processes within 104‐s duration of this event. Constrained by the field observed runout distance, we deduce the landslide's mass of about 9 × 109 kg with corresponding maximum velocity and acceleration of 58.8 m/s and 4.38 m/s2, respectively. Combining dynamic parameters, apparent friction coefficient, and seismic signal features, we depict a dynamic landslide process initiated by high‐position rockslide, traveled by rapid long runout debris, and deposited over an old landslide's deposition fan. The rapid process of the landslide is affected by multiple preconditions such as the structure, topography, and meteorology of the site, which is characteristic of a typical chain‐style landslide hazard and could be helpful to recognize potential slope instabilities.

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Section: Discussionmentioning

confidence: 99%

“…The apparent friction coefficient is considered as the effects of both true friction coefficient ( μ ′ ) and basal fluid pressure ( P ; Iverson, ):

μ σ_{n} = μ^{'} ((), σ_{n} - P)

Section: Discussionmentioning

confidence: 99%

Chain‐Style Landslide Hazardous Process: Constraints From Seismic Signals Analysis of the 2017 Xinmo Landslide, SW China

Chen

et al. 2019

JGR Solid Earth

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“…In the last 20 years, the advent of the so called high-speed rotary shear machines, allowed us to reproduce deformation conditions that approach those achieved at the rupture front during seismic slip [4]. From these experiments it became clear that more or less independently of the lithology, fault rocks undergo profound weakening when a critical slip rate V w of 0.01-0.1 m/s is exceeded [2,5,6].…”

Section: Introductionmentioning

confidence: 99%

Dislocation Motion and the Microphysics of Flash Heating and Weakening of Faults during Earthquakes

et al. 2016

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Abstract:Earthquakes are the result of slip along faults and are due to the decrease of rock frictional strength (dynamic weakening) with increasing slip and slip rate. Friction experiments simulating the abrupt accelerations (>>10 m/s 2 ), slip rates (~1 m/s), and normal stresses (>>10 MPa) expected at the passage of the earthquake rupture along the front of fault patches, measured large fault dynamic weakening for slip rates larger than a critical velocity of 0.01-0.1 m/s. The dynamic weakening corresponds to a decrease of the friction coefficient (defined as the ratio of shear stress vs. normal stress) up to 40%-50% after few millimetres of slip (flash weakening), almost independently of rock type. The microstructural evolution of the sliding interfaces with slip may yield hints on the microphysical processes responsible for flash weakening. At the microscopic scale, the frictional strength results from the interaction of micro-to nano-scale surface irregularities (asperities) which deform during fault sliding. During flash weakening, the visco-plastic and brittle work on the asperities results in abrupt frictional heating (flash heating) and grain size reduction associated with mechano-chemical reactions (e.g., decarbonation in CO 2 -bearing minerals such as calcite and dolomite; dehydration in water-bearing minerals such as clays, serpentine, etc.) and phase transitions (e.g., flash melting in silicate-bearing rocks). However, flash weakening is also associated with grain size reduction down to the nanoscale. Using focused ion beam scanning and transmission electron microscopy, we studied the micro-physical mechanisms associated with flash heating and nanograin formation in carbonate-bearing fault rocks. Experiments were conducted on pre-cut Carrara marble (99.9% calcite) cylinders using a rotary shear apparatus at conditions relevant to seismic rupture propagation. Flash heating and weakening in calcite-bearing rocks is associated with a shock-like stress release due to the migration of fast-moving dislocations and the conversion of their kinetic energy into heat. From a review of the current natural and experimental observations we speculate that this mechanism tested for calcite-bearing rocks, is a general mechanism operating during flash weakening (e.g., also precursory to flash melting in the case of silicate-bearing rocks) for all fault rock types undergoing fast slip acceleration due to the passage of the seismic rupture front.

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“…To illustrate the effect of the velocity dependence in (3.16) on fault stability, we can compute the corresponding critical frictional stiffness (again assuming that we are close to the steady state and that inertia is negligible). Taking the indicative value p = 1 in (3.16), we obtain where we retrieve k c as of (3.15) in the limit V V c , but here the critical stiffness varies and peaks substantially in the vicinity of V = V c , as argued in [72]. This indicates that fault instability is enhanced if the experimentally observed velocity weakening is allowed to kick in.…”

Section: Challenging Observations (A) Dissipation: Is It Only Friction?mentioning

confidence: 75%

“…The experimental foundation for such an empirical formulation was subsequently demonstrated by Spagnuolo et al [72] based on high velocity, rotary shear experiments on slica-built and carbonate-built cohesive rocks. Such formulation can be synthetized as follows:…”

Section: Challenging Observations (A) Dissipation: Is It Only Friction?mentioning

confidence: 99%

From slow to fast faulting: recent challenges in earthquake fault mechanics

Nielsen

2017

Phil. Trans. R. Soc. A.

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Faults—thin zones of highly localized shear deformation in the Earth—accommodate strain on a momentous range of dimensions (millimetres to hundreds of kilometres for major plate boundaries) and of time intervals (from fractions of seconds during earthquake slip, to years of slow, aseismic slip and millions of years of intermittent activity). Traditionally, brittle faults have been distinguished from shear zones which deform by crystal plasticity (e.g. mylonites). However such brittle/plastic distinction becomes blurred when considering (i) deep earthquakes that happen under conditions of pressure and temperature where minerals are clearly in the plastic deformation regime (a clue for seismologists over several decades) and (ii) the extreme dynamic stress drop occurring during seismic slip acceleration on faults, requiring efficient weakening mechanisms. High strain rates (more than 10 4 s −1 ) are accommodated within paper-thin layers (principal slip zone), where co-seismic frictional heating triggers non-brittle weakening mechanisms. In addition, (iii) pervasive off-fault damage is observed, introducing energy sinks which are not accounted for by traditional frictional models. These observations challenge our traditional understanding of friction (rate-and-state laws), anelastic deformation (creep and flow of crystalline materials) and the scientific consensus on fault operation. This article is part of the themed issue ‘Faulting, friction and weakening: from slow to fast motion’.

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An empirically based steady state friction law and implications for fault stability

Cited by 40 publications

References 62 publications

Chain‐Style Landslide Hazardous Process: Constraints From Seismic Signals Analysis of the 2017 Xinmo Landslide, SW China

Chain‐Style Landslide Hazardous Process: Constraints From Seismic Signals Analysis of the 2017 Xinmo Landslide, SW China

Dislocation Motion and the Microphysics of Flash Heating and Weakening of Faults during Earthquakes

From slow to fast faulting: recent challenges in earthquake fault mechanics

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