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 Seismicity recorded in hematite fault mirrors in the Rio Grande rift

Geosphere ◽  
2021 ◽  
Author(s):  
M.L. Odlum ◽  
A.K. Ault ◽  
M.A. Channer ◽  
G. Calzolari
Keyword(s):  
High Temperature ◽  
Fault Zone ◽  
Temperature Rise ◽  
Rio Grande ◽  
Fault Slip ◽  
Fault Reactivation ◽  
Rio Grande Rift ◽  
Seismogenic Zone ◽  
Size Dependent ◽  
Slip Surfaces

Exhumed fault rocks provide a textural and chemical record of how fault zone composition and architecture control coseismic temperature rise and earthquake mechanics. We integrated field, microstructural, and hematite (U-Th)/He (He) thermochronometry analyses of exhumed minor (square-centimeter-scale surface area) hematite fault mirrors that crosscut the ca. 1400 Ma Sandia granite in two localities along the eastern flank of the central Rio Grande rift, New Mexico. We used these data to characterize fault slip textures; evaluate relationships among fault zone composition, thickness, and inferred magnitude of friction-generated heat; and document the timing of fault slip. Hematite fault mirrors are collocated with and crosscut specular hematite veins and hematite-cemented cataclasite. Observed fault mirror microstructures reflect fault reactivation and strain localization within the comparatively weaker hematite relative to the granite. The fault mirror volume of some slip surfaces exhibits polygonal, sintered hematite nanoparticles likely created during coseismic temperature rise. Individual fault mirror hematite He dates range from ca. 97 to 5 Ma, and ~80% of dates from fault mirror volume aliquots with high-temperature crystal morphologies are ca. 25–10 Ma. These aliquots have grain-size–dependent closure temperatures of ~75–108 °C. A new mean apatite He date of 13.6 ± 2.6 Ma from the Sandia granite is consistent with prior low-temperature thermochronometry data and reflects rapid, Miocene rift flank exhumation. Comparisons of thermal history models and hematite He data patterns, together with field and microstructural observations, indicate that seismicity along the fault mirrors at ~2–4 km depth was coeval with rift flank exhumation. The prevalence and distribution of high-temperature hematite grain morphologies on different slip surfaces correspond with thinner deforming zones and higher proportions of quartz and feldspar derived from the granite that impacted the bulk strength of the deforming zone. Thus, these exhumed fault mirrors illustrate how evolving fault material properties reflect but also govern coseismic temperature rise and associated dynamic weakening mechanisms on minor faults at the upper end of the seismogenic zone.

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 Adsorption Studies on Magnetic Nanoparticles Functionalized with Silver to Remove Nitrates from Waters

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1757
Author(s):  
Yesica Vicente-Martínez ◽  
Manuel Caravaca ◽  
Antonio Soto-Meca ◽  
Miguel Ángel Martín-Pereira ◽  
María del Carmen García-Onsurbe
Keyword(s):  
Magnetic Nanoparticles ◽  
Nitrate Content ◽  
Adsorption Efficiency ◽  
Experimental Conditions ◽  
Dependent Behavior ◽  
Before And After ◽  
Naoh Solution ◽  
High Concentrations ◽  
Interference Studies

This paper presents a novel procedure for the treatment of contaminated water with high concentrations of nitrates, which are considered as one of the main causes of the eutrophication phenomena. For this purpose, magnetic nanoparticles functionalized with silver (Fe3O4@AgNPs) were synthesized and used as an adsorbent of nitrates. Experimental conditions, including the pH, adsorbent and adsorbate dose, temperature and contact time, were analyzed to obtain the highest adsorption efficiency for different concentration of nitrates in water. A maximum removal efficiency of 100% was reached for 2, 5, 10 and 50 mg/L of nitrate at pH = 5, room temperature, and 50, 100, 250 and 500 µL of Fe3O4@AgNPs, respectively. The characterization of the adsorbent, before and after adsorption, was performed by energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Nitrates can be desorbed, and the adsorbent can be reused using 500 µL of NaOH solution 0.01 M, remaining unchanged for the first three cycles, and exhibiting 90% adsorption efficiency after three regenerations. A deep study on equilibrium isotherms reveals a pH-dependent behavior, characterized by Langmuir and Freundlich models at pH = 5 and pH = 1, respectively. Thermodynamic studies were consistent with physicochemical adsorption for all experiments but showed a change from endothermic to exothermic behavior as the temperature increases. Interference studies of other ions commonly present in water were carried out, enabling this procedure as very selective for nitrate ions. In addition, the method was applied to real samples of seawater, showing its ability to eliminate the total nitrate content in eutrophized waters.

scholarly journals Experimental Study on the Water Selective Dense Membrane under an Absolute Pressure Difference with Simplified Test Method

2021 ◽  
Vol 11 (4) ◽  
pp. 1710
Author(s):  
Jinwook Lee ◽  
Hyo-Sun Kim ◽  
Donik Ku ◽  
Jihun Lim ◽  
Minkyu Jung ◽  
...  
Keyword(s):  
Measurement Methods ◽  
Test Method ◽  
Coefficient Of Performance ◽  
Absolute Pressure ◽  
Air Conditioner ◽  
Experimental Conditions ◽  
Simple Method ◽  
Performance Factors ◽  
Dense Membrane ◽  
Before And After

Membrane-based vacuum dehumidification technology is currently being actively studied. In most studies, the performance of the membrane-based systems is evaluated under the assumption that the membrane can achieve ideal separation, which results in ideal coefficient of performance (COP) values. However, the performance factors for membranes vary depending on the experimental conditions and measurement methods. Therefore, relevant values can only be calculated if the data are measured in an environment close to that of the application conditions. The cup measurement method is a simple method to measure the permeability, however, there are limitations regarding adding variables during the experiment. To overcome these limitations, a new experimental device was constructed that combines pressurized cell with the cup method. Using the device, the performance of polyethylene-amide-bonded dense membranes was evaluated under conditions where absolute pressure differentials occurred before and after the membrane, such as in air conditioner dehumidification systems.

Caffeine counteracts the ergogenic action of muscle creatine loading

1996 ◽  
Vol 80 (2) ◽  
pp. 452-457 ◽  
Author(s):  
K. Vandenberghe ◽  
N. Gillis ◽  
M. Van Leemputte ◽  
P. Van Hecke ◽  
F. Vanstapel ◽  
...  
Keyword(s):  
Intermittent Exercise ◽  
Creatine Supplementation ◽  
Knee Extensors ◽  
Caffeine Intake ◽  
Resonance Spectroscopy ◽  
Experimental Conditions ◽  
Before And After ◽  
And Performance ◽  
Exercise Fatigue ◽  
Voluntary Contractions

This study aimed to compare the effects of oral creatine (Cr) supplementation with creatine supplementation in combination with caffeine (Cr+C) on muscle phosphocreatine (PCr) level and performance in healthy male volunteers (n = 9). Before and after 6 days of placebo, Cr (0.5 g x kg-1 x day-1), or Cr (0.5 g x kg-1 x day-1) + C (5 mg x kg-1 x day-1) supplementation, 31P-nuclear magnetic resonance spectroscopy of the gastrocnemius muscle and a maximal intermittent exercise fatigue test of the knee extensors on an isokinetic dynamometer were performed. The exercise consisted of three consecutive maximal isometric contractions and three interval series of 90, 80, and 50 maximal voluntary contractions performed with a rest interval of 2 min between the series. Muscle ATP concentration remained constant over the three experimental conditions. Cr and Cr+C increased (P < 0.05) muscle PCr concentration by 4-6%. Dynamic torque production, however, was increased by 10-23% (P < 0.05) by Cr but was not changed by Cr+C. Torque improvement during Cr was most prominent immediately after the 2-min rest between the exercise bouts. The data show that Cr supplementation elevates muscle PCr concentration and markedly improves performance during intense intermittent exercise. This ergogenic effect, however, is completely eliminated by caffeine intake.

scholarly journals Running velocity at the ventilatory threshold and at VO2max, before and after the eight-week cardiovascular endurance training

2005 ◽  
Vol 58 (1-2) ◽  
pp. 27-31
Author(s):  
Stanimir Stojiljkovic ◽  
Sanja Mazic ◽  
Dejan Nesic ◽  
Sasko Velkovski ◽  
Dusan Mitrovic
Keyword(s):  
Endurance Training ◽  
Ventilatory Threshold ◽  
Exercise Program ◽  
Test Results ◽  
Final Test ◽  
Experimental Conditions ◽  
Cardiovascular Endurance ◽  
Before And After ◽  
Test Velocity ◽  
Male Subjects

Introduction The purpose of this research was to compare changes in running velocity at ventilatory threshold with the veliocity at VO2max, before and after the eight-week exercise program. Material and methods 32 male subjects (age: 22.3? 2.5 years, height: 179.8? 7.6 cm, body mass: 76.8? 9.0 kg) performed a progressive test for ventilatory threshold (VT) measurement and VO2max on treadmill. After 8 weeks of endurance training (3 times per week, 30 to 70 min, in different zones in respect to the ventilatory threshold) the performed the same test. Results Running velocity at ventilatory threshold increased significantly (p=0.000I), between initial and final measurements (10.88?2.09, 12.94? 1.90 km/h, respectively): as well as at VO2max H4.63?1.86, 16.44?1.59 km/h, respectively). At the initial test, velocity at ventilatory threshold was 74.11% of VO2max. At the final test, velocity at ventilatory threshold was 78.43% of VO2max. Running velocity at ventilatory threshold has significantly increased at final test (p=0.001). Discussion Running velocity at ventilatory threshold has significantly increased after eight weeks of endurance training (p -0.001), when expressed in absolute values and percentage of velocity at vo2max. Conclusion Comparison between the initial and final test demonstrated a significant increase of observed variables, under experimental conditions: at final test running velocity has increased at ventilatory threshold, in respect to absolute values and expressed as percentage at VO2max. .

Sign in / Sign up

Export Citation Format

Share Document