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  • 1
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    Is frictional heating needed to cause dramatic weakening of nanoparticle gouge during seismic slip? Insights from friction experiments with variable thermal evolutions (2016)
    Wiley
    Details
    Publication Date: 2016-06-24
    Description: To examine whether faults can be lubricated by preexisting and newly-formed nanoparticles, we perform high-velocity friction experiments on periclase (MgO) nanoparticles and on bare surfaces of Carrara marble cylinders/slices, respectively. Variable temperature conditions were simulated by using host blocks of different thermal conductivities. When temperature rises are relatively low, we observe high friction in nano-MgO tests and unexpected slip strengthening following initial weakening in marble slice tests, suggesting that the dominant weakening mechanisms are of thermal origin. Solely the rolling of nanoparticles without significant temperature rise is insufficient to cause dynamic fault weakening. For nano-MgO experiments, comprehensive investigations suggest that flash heating is the most likely weakening mechanism. In marble experiments, flash heating controls the unique evolutions of friction, and the competition between bulk temperature rise and wear-induced changes of asperity-contact numbers seems to strongly affect the efficiency of flash heating.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    High-velocity frictional strength of Longmenshan fault gouge and its comparison with an estimate of friction from the temperature anomaly in WFSD-1 drill hole (2016)
    Wiley
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    Publication Date: 2016-06-28
    Description: This paper addresses the issue of whether high-velocity friction experiments yield frictional strengths of fault materials that are consistent with the level of friction estimated from the post-seismic temperature anomaly measured across a coseismic fault zone. Experiments were conducted on gouge (composed of quartz, dolomite, illite, albite and other clay minerals), collected from a large outcrop of the Yingxiu-Beichuan fault zone and from WFSD-1 (Wenchuan Earthquake Fault Scientific Drilling) drill cores in Hongkou, Sichuan province, China. This fault is a major fault of the Longmenshan fault system that caused the 2008 M w 7.9 Wenchuan earthquake. All experiments revealed dramatic weakening at high velocities with peak friction coefficient μ p of 0.07 ~ 0.35 and steady-state friction coefficient μ ss of 0.02 ~ 0.15 for wet gouge, as compared with μ p  = 0.49 ~ 0.86 and μ ss  = 0.12 ~ 0.21 for dry gouge. The average friction coefficients over a displacement of 5.5 m (coseismic displacement) extrapolated to the normal stress in the fault zones are 0.1 ~ 0.05 and 0.06 ~ 0.03 for dry and wet gouges, respectively. The average friction coefficients of dry and wet gouge are within the upper and lower bounds of friction coefficients estimated from the temperature profiles, and there are overall agreements between the two sets of data that are completely independent. Dry and wet gouges are characterized by highly-sheared slip zones often forming overlapping slip-zone structures and by broad shear zones, respectively. Wet gouge textures are perhaps closer to those of natural fault zone, but repeated slip experiments are needed to determine the textural evolution of wet gouge.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 3
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    Correction to “Low- to high-velocity frictional properties of the clay-rich gouges from the slipping zone of the 1963 Vaiont slide, northern Italy” (2011)
    Wiley
    Details
    Publication Date: 2011-11-09
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 4
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    Low- to high-velocity frictional properties of the clay-rich gouges from the slipping zone of the 1963 Vaiont slide, northern Italy (2011)
    Wiley
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    Publication Date: 2011-09-28
    Description: The final slip of about 450 m at about 30 m/s of the 1963 Vaiont landslide (Italy) was preceded by 〉3 year long creeping phase which was localized in centimeter-thick clay-rich layers (60–70% smectites, 20–30% calcite and quartz). Here we investigate the frictional properties of the clay-rich layers under similar deformation conditions as during the landslide: 1–5 MPa normal stress, 2 × 10−7 to 1.31 m/s slip rate and displacements up to 34 m. Experiments were performed at room humidity and wet conditions with biaxial, torsion and rotary shear apparatus. The clay-rich gouge was velocity-independent to velocity-weakening in both room humidity and wet conditions. In room humidity experiments, the coefficient of friction decreased from 0.47 at v 〈 5.0 × 10−5 m/s to 0.12 at 1.31 m/s. Microstructural and mineralogical analyses of the gouge after experiments indicate that the dramatic weakening results from thermo-chemical pressurization of pore fluids (smectite decomposition to illite-type clays) and powder lubrication. In wet experiments, the coefficient of friction decreased from 0.17 at v 〈 1.0 × 10−4 m/s to 0.0 at v 〉 0.70 m/s: full lubrication results from the formation of a continuous water film in the gouge. The Vaiont landslide occurred under wet to saturated conditions. The unstable behavior of the landslide is explained by the velocity-weakening behavior of the Vaiont clay-rich gouges. The formation of a continuous film of liquid water in the slipping zone reduced the coefficient of friction to almost zero, even without invoking the activation of thermal pressurization. This explains the extraordinary high velocity achieved by the slide during the final collapse.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
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    A Friction to flow constitutive law and its application to a 2D-modeling of earthquakes (2014)
    Wiley
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    Publication Date: 2014-10-14
    Description: Establishment of a constitutive law from friction to high-temperature plastic flow has long been a challenging task for solving problems such as modeling earthquakes and plate interactions. Here we propose an empirical constitutive law that describes this transitional behavior using only friction and flow parameters, with good agreements with experimental data on halite shear zones. The law predicts steady-state and transient behaviors, including the dependence of the shear resistance of fault on slip rate, effective normal stress and temperature. It also predicts a change in velocity-weakening to velocity-strengthening with increasing temperature, similar to the changes recognized for quartz and granite gouge under hydrothermal conditions. A slight deviation from the steady-state friction law due to the involvement of plastic deformation can cause a large change in the velocity dependence. We solved seismic cycles of a fault across the lithosphere with the law using a 2D spectral boundary integral equation method, revealing dynamic rupture extending into the aseismic zone and rich evolution of interseismic creep including slow slip prior to earthquakes. Seismic slip followed by creep is consistent with natural pseudotachylytes overprinted with mylonitic deformation. Overall fault behaviors during earthquake cycles are insensitive to transient flow parameters. The friction-to-flow law merges “Christmas-tree” strength profiles of the lithosphere and rate-dependency fault models used for earthquake modeling on a unified basis. Strength profiles were drawn assuming a strain rate for the flow regime, but we emphasize that stress distribution evolves reflecting the fault behavior. A fault-zone model was updated based on the earthquake modeling.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Triggering and runaway processes of catastrophic Tsaoling landslide induced by the 1999 Taiwan Chi-Chi earthquake, as revealed by high-velocity friction experiments (2014)
    Wiley
    Details
    Publication Date: 2014-03-19
    Description: Pliocene sedimentary rocks of about 130 Mm 3 in volume slid along bedding planes dipping by 14°, with an average speed of about 35 m/s, during the Tsaoling landslide. We conducted friction experiments to reproduce the initiation processes of this landslide, by idealizing landslide movements during the earthquake as accelerating/decelerating motion. Experiments were done on shale from the field, at 3 MPa normal stress corresponding to the overburden pressure. Results indicate that the accelerating/decelerating motion causes weakening and strengthening at each oscillation cycle and results in overall slip weakening which can be approximated as an exponential slip weakening. Behaviors during oscillatory slip are fairly similar to those during sliding at constant slip rates. Newmark analysis with measured frictional properties reveals that the landslide can be triggered with wet gouge properties, but the landslide motion stops with parameters for dry shale gouge. Delayed initiation of the landslide is consistent with a survivor's witness.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Graphite as a lubricating agent in fault zones: an insight from low- to high-velocity friction experiments on a mixed graphite–quartz gouge (2013)
    Wiley
    Details
    Publication Date: 2013-04-04
    Description: [1]  Graphite is a very low-friction material, often enriched within fault zones due to mechanical or chemical processes. The effects of weak minerals on the strength of faults have been examined by friction experiments on bimineralic mixtures. However, previous experiments were conducted with limited shear strains, even though applied shear strains and textural developments had already been signaled as significant factors in the weakening of faults. We therefore conducted large-displacement, low- to high-velocity friction experiments with graphite–quartz gouges, to determine how much graphite is needed to reduce frictional strength, and to examine how textures contribute to the strength reduction of a mature fault at various slip rates. We found that the coefficients of friction of the gouges decrease non-linearly with increasing graphite fraction for any given shear strain and slip rate, decreasing first with 5–20 vol% graphite, then reaching similar frictional levels to pure graphite with 30–50 vol% graphite. The non-linear weakening trends can be fitted by sigmoidal curves. The weakening with 10–30 vol% graphite is associated with zones of slip-localization and the development of a graphite-lubricated penetrative slip surface(s). With increasing shear strain, the relationship between strength and graphite fraction evolves abruptly from an early gentle curve to a sigmoidal curve, and the frictional strength drops significantly even with small amounts of graphite (ca. 10 vol%). Our results highlight the importance of shear strain and textural developments on weak faults, not only with respect to graphite, but also other fault lubricants such as the phyllosilicates.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 8
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    Rapid post-seismic strength recovery of Pingxi fault gouge from the Longmenshan fault system: Experiments and implications for the mechanisms of high-velocity weakening of faults (2013)
    Wiley
    Details
    Publication Date: 2013-07-31
    Description: [1]  Slide-hold-slide (SHS) tests were conducted on gray blackish gouge (GBG) and yellowish gouge (YG) from Pingxi fault zone to see how rapidly the strength of Longmenshan fault recovers after the 2008 Wenchuan earthquake. Twenty dry runs were made at a normal stress of 0.8 MPa, at a seismic slip rate of 1.4 m/s and with hold time t h ranging 0.3 ~ 10 5  s. Results exhibit very rapid healing by more than 0.4 in friction coefficient μ in less than 5 ~ 10 s, followed by gradual healing in proportion to log( t h ). Healing rates, (increase in μ)/(log t h ), during rapid and slow healing are 0.188 and 0.015 for GBG and 0.154 and 0.016 for YG, respectively. The average temperature in the outer half of a 5 µm-thick slip zone decreases from 260 ~ 300 °C to 110 ~ 170 °C in 5 ~ 10 s and hence temperature drop appears to be correlated with the rapid healing. Previously-reported rapid healing at subseismic slip rates (85 ~ 90 mm/s) begins to occur in 10 ~ 300 s after the stop of sliding and this cannot be explained by the cooling of gouge. The difference in healing between subseismic slip rates (delayed and rapid healing) and seismic slip rates (immediate and rapid healing) suggests that the dominant weakening mechanism shifts from tribochemical processes at subseismic slip rates to frictional heating at seismic slip rates. Slip-zone structures are too complex and variable from run to run to reveal microscopic mechanisms for the strength recovery. Rapid healing following seismic slip can be a cause for reduced aftershocks along major coseismic faults.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative study of cataclastic rocks from a drill core and outcrops of the Nojima Fault zone on Awaji Island, Japan (2001)
    Melbourne, Australia : Blackwell Science Pty
    The @island arc 10 (2001), S. 0 
    Details
    ISSN: 1440-1738
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Cataclastic rocks found in the Disaster Prevention Research Institute, Kyoto University (DPRI) 500 m drill core and outcrops along the Nojima Fault zone on Awaji Island, southwest Japan, were examined at mesoscopic and microscopic scales. The damaged zone of this fault in granitic rocks, observed on the southeast side of the fault, is 50–60 m wide and is composed of fractured host rocks and cataclastic rocks including cataclasite, fault breccia, and fault gouge. The fault breccia and gouge of small scales are scattered in the damaged zone. Fault core (zone of extremely concentrated shearing deformation along a fault) consists of fault gouge measuring several tens to approximately 150 mm in width, as recognized both in the drill core and at outcrops of the Nojima Fault along which surface ruptures formed during the 1995 Kobe earthquake. Fault breccia, measuring a few meters wide, has developed pervasively in the damaged zone, just next to the fault core. Pseudotachylyte has been found interlayered with fault gouge within the fault core only at outcrops at Hirabarashi, not in the DPRI 500 m core. Petrological studies and powder X-ray diffraction analysis show that the pseudotachylyte and fault gouge are composed mainly of fine-grained angular clasts of the host granitic rocks, suggesting the pseudotachylyte is of ‘crush origin’. Foliated cataclasite is characterized by the preferred orientation of elongated biotite clasts and granular aggregates of quartz and feldspar clasts, and by the development of cataclastic shear bands. Unlike cataclastically deformed quartz and feldspar in the cataclasite, biotite in the foliated cataclasite shows combinations of brittle and plastic deformation, such as biotite ‘fish’, cleavage steps, bending and kinking. These textures suggest that the foliated cataclasite formed at a deeper level than the cataclasite, fault breccia and gouge, possibly before the Quaternary period during which the Nojima Fault has moved as a dextral strike–slip fault with some reverse movement resulting in the uplifting of Awaji Island. Examination of fault rocks from surface outcrops can yield similar results to those obtained from drill cores with regard to the internal structures of a fault zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1738.2001.00335.x
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  • 10
    Electronic Resource
    Electronic Resource
    Earthquake slip weakening and asperities explained by thermal pressurization (2005)
    [s.l.] : Nature Publishing Group
    Nature 436 (2005), S. 689-692 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] An earthquake occurs when a fault weakens during the early portion of its slip at a faster rate than the release of tectonic stress driving the fault motion. This slip weakening occurs over a critical distance, Dc. Understanding the controls on Dc in nature is severely ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03901
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