scholarly journals Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

2014 ◽  
Vol 119 (11) ◽  
pp. 8107-8131 ◽  
Author(s):  
B. P. Proctor ◽  
T. M. Mitchell ◽  
G. Hirth ◽  
D. Goldsby ◽  
F. Zorzi ◽  
...  
Keyword(s):  
Slip Rates ◽  
Seismic Slip ◽  
Dynamic Weakening

scholarly journals Hematite (U-Th)/He thermochronometry detects asperity flash heating during laboratory earthquakes

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 514-518 ◽  
Author(s):  
Gabriele Calzolari ◽  
Alexis K. Ault ◽  
Greg Hirth ◽  
Robert G. McDermott
Keyword(s):  
High Temperatures ◽  
Temperature Rise ◽  
Thick Layer ◽  
Seismogenic Zone ◽  
Experimental Conditions ◽  
Slip Rates ◽  
Seismic Slip ◽  
Slip Surfaces ◽  
Before And After ◽  
Dynamic Weakening

Abstract Evidence for coseismic temperature rise that induces dynamic weakening is challenging to directly observe and quantify in natural and experimental fault rocks. Hematite (U-Th)/He (hematite He) thermochronometry may serve as a fault-slip thermometer, sensitive to transient high temperatures associated with earthquakes. We test this hypothesis with hematite deformation experiments at seismic slip rates, using a rotary-shear geometry with an annular ring of silicon carbide (SiC) sliding against a specular hematite slab. Hematite is characterized before and after sliding via textural and hematite He analyses to quantify He loss over variable experimental conditions. Experiments yield slip surfaces localized in an ∼5–30-µm-thick layer of hematite gouge with <300-µm-diameter fault mirror (FM) zones made of sintered nanoparticles. Hematite He analyses of undeformed starting material are compared with those of FM and gouge run products from high-slip-velocity experiments, showing >71% ± 1% (1σ) and 18% ± 3% He loss, respectively. Documented He loss requires short-duration, high temperatures during slip. The spatial heterogeneity and enhanced He loss from FM zones are consistent with asperity flash heating (AFH). Asperities >200–300 µm in diameter, producing temperatures >900 °C for ∼1 ms, can explain observed He loss. Results provide new empirical evidence describing AFH and the role of coseismic temperature rise in FM formation. Hematite He thermochronometry can detect AFH and thus seismicity on natural FMs and other thin slip surfaces in the upper seismogenic zone of Earth’s crust.

scholarly journals Frictional properties and microstructural evolution of dry and wet calcite–dolomite gouges

Solid Earth ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 595-612
Author(s):  
Matteo Demurtas ◽  
Steven A.F. Smith ◽  
Elena Spagnuolo ◽  
Giulio Di Toro
Keyword(s):  
Microstructural Evolution ◽  
Normal Load ◽  
Shear Zones ◽  
Slip Zone ◽  
Cyclic Process ◽  
Experimental Conditions ◽  
Slip Rates ◽  
Bearing Faults ◽  
Seismic Slip ◽  
Dynamic Weakening

Abstract. Calcite and dolomite are the two most common minerals in carbonate-bearing faults and shear zones. Motivated by observations of exhumed seismogenic faults in the Italian Central Apennines, we used a rotary-shear apparatus to investigate the frictional and microstructural evolution of ca. 3 mm thick gouge layers consisting of 50 wt % calcite and 50 wt % dolomite. The gouges were sheared at a range of slip rates (30 µm s−1–1 m s−1), displacements (0.05–0.4 m), and a normal load of 17.5 MPa under both room-humidity and water-dampened conditions. The frictional behaviour and microstructural evolution of the gouges were strongly influenced by the presence of water. At room humidity, slip strengthening was observed up to slip rates of 0.01 m s−1, which was associated with gouge dilation and the development of a 500–900 µm wide slip zone cut by Y-, R-, and R1-shear bands. Above a slip rate of 0.1 m s−1, dynamic weakening accompanied the development of a localised < 100 µm thick principal slip zone preserving microstructural evidence for calcite recrystallisation and dolomite decarbonation, while the bulk gouges developed a well-defined foliation consisting of organised domains of heavily fractured calcite and dolomite. In water-dampened conditions, evidence of gouge fluidisation within a fine-grained principal slip zone was observed at a range of slip rates from 30 µm s−1 to 0.1 m s−1, suggesting that caution is needed when relating fluidisation textures to seismic slip in natural fault zones. Dynamic weakening in water-dampened conditions was observed at 1 m s−1, where the principal slip zone was characterised by patches of recrystallised calcite. However, local fragmentation and reworking of recrystallised calcite suggests a cyclic process involving formation and destruction of a heterogeneous slip zone. Our microstructural data show that development of well-defined gouge foliation under the tested experimental conditions is limited to high velocities (>0.1 m s−1) and room humidity, supporting the notion that some foliated gouges and cataclasites may form during seismic slip in natural carbonate-bearing faults.

scholarly journals Frictional properties and microstructural evolution of dry and wet calcite-dolomite gouges

2020 ◽  
Author(s):  
Matteo Demurtas ◽  
Steven A.F. Smith ◽  
Elena Spagnuolo ◽  
Giulio Di Toro
Keyword(s):  
Microstructural Evolution ◽  
Shear Zones ◽  
Slip Zone ◽  
Cyclic Process ◽  
Experimental Conditions ◽  
Slip Rates ◽  
Bearing Faults ◽  
Seismic Slip ◽  
Wide Range ◽  
Dynamic Weakening

Abstract. Calcite and dolomite are the two most common minerals in carbonate-bearing faults and shear zones. Motivated by field examples from exhumed seismogenic faults in the Italian Central Apennines, we investigated the frictional and microstructural evolution of gouge mixtures consisting of 50 wt % calcite and 50 wt % dolomite using a rotary-shear apparatus. The gouges were sheared at a range of slip rates (30 µm s−1–1 m s−1), displacements (0.05–0.4 m), and normal loads (17.5–26 MPa), under both room humidity and water-dampened conditions. The frictional behaviour and microstructural evolution of the gouges were strongly influenced by the presence of water. At room humidity, slip strengthening behaviour was observed up to slip rates of 0.01 m s−1, which was associated with gouge dilation and the development of a 500–900 µm wide slip zone cut by Y-, R-, and R1-shear bands. Above a slip rate of 0.1 m s−1, dynamic weakening accompanied the development of a localised <100 µm thick principal slip zone preserving microstructural evidence for calcite recrystallization and dolomite decarbonation, while the bulk gouges developed a well-defined foliation consisting of organized domains of heavily fractured calcite and dolomite. In water-dampened conditions, evidence of gouge fluidization within a fine-grained principal slip zone was observed at a wide range of slip-rates from 30 µm s−1 to 0.1 m s−1, suggesting that caution is needed when relating fluidization textures to seismic slip in natural fault zones. Dynamic weakening in water-dampened conditions was observed at 1 m s−1, where the principal slip zone was characterised by patches of recrystallized calcite. However, local fragmentation and reworking of recrystallized calcite suggests a cyclic process involving formation and destruction of a heterogeneous slip zone. Our microstructural data show that development of a well-defined gouge foliation at these experimental conditions is limited to high-velocity (>0.1 m s−1) and room humidity, supporting the notion that some foliated gouges and cataclasites may form during seismic slip in natural carbonate-bearing faults.

scholarly journals Frictional evolution, acoustic emissions activity, and off-fault damage in simulated faults sheared at seismic slip rates

2016 ◽  
Vol 121 (10) ◽  
pp. 7490-7513 ◽  
Author(s):  
François. X. Passelègue ◽  
Elena Spagnuolo ◽  
Marie Violay ◽  
Stefan Nielsen ◽  
Giulio Di Toro ◽  
...  
Keyword(s):  
Acoustic Emissions ◽  
Slip Rates ◽  
Seismic Slip

scholarly journals Flash weakening of serpentinite at near-seismic slip rates

2011 ◽  
Vol 116 (B3) ◽  
Author(s):  
Arjun H. Kohli ◽  
David L. Goldsby ◽  
Greg Hirth ◽  
Terry Tullis
Keyword(s):  
Slip Rates ◽  
Seismic Slip

Moisture-related weakening and strengthening of a fault activated at seismic slip rates

2006 ◽  
Vol 33 (16) ◽  
Author(s):  
Kazuo Mizoguchi ◽  
Takehiro Hirose ◽  
Toshihiko Shimamoto ◽  
Eiichi Fukuyama
Keyword(s):  
Slip Rates ◽  
Seismic Slip

Nanocrystalline slip zones in calcite fault gouge show intense crystallographic preferred orientation: Crystal plasticity at sub-seismic slip rates at 18–150 °C

Geology ◽  
2013 ◽  
Vol 41 (8) ◽  
pp. 863-866 ◽  
Author(s):  
Berend A. Verberne ◽  
Johannes H.P. de Bresser ◽  
André R. Niemeijer ◽  
Christopher J. Spiers ◽  
D.A. Matthijs de Winter ◽  
...  
Keyword(s):  
Crystal Plasticity ◽  
Fault Gouge ◽  
Preferred Orientation ◽  
Slip Rates ◽  
Crystallographic Preferred Orientation ◽  
Seismic Slip

Seismic slip rates in the Mediterranean and Middle East

Nature ◽  
1974 ◽  
Vol 252 (5484) ◽  
pp. 560-563 ◽  
Author(s):  
ROBERT G. NORTH
Keyword(s):  
Middle East ◽  
Slip Rates ◽  
Seismic Slip ◽  
The Mediterranean
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