scholarly journals Fast and localized temperature measurements during simulated earthquakes in carbonate rocks

2021 ◽  
Author(s):  
Giulio Di Toro ◽  
Stefano Aretusini ◽  
Arántzazu Núñez-Cascajero ◽  
Elena Spagnuolo ◽  
Alberto Tapetado ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Seismic Velocity ◽  
Frictional Heating ◽  
Temperature Measurements ◽  
Temperature Evolution ◽  
Earthquake Physics ◽  
Fault Surface ◽  
Total Displacement ◽  
Fault Strength ◽  
Marble Rock

<p>The understanding of earthquake physics is hindered by the poor knowledge of fault strength and temperature evolution during seismic slip. Experiments reproducing seismic velocity (~1 m/s) allow us to measure both the evolution of fault strength and the associated temperature increase due to frictional heating. However, temperature measurements were performed with techniques having insufficient spatial and temporal resolution. Here we conduct high velocity friction experiments on Carrara marble rock samples sheared at 20 MPa normal stress, velocity of 0.3 and 6 m/s, and 20 m of total displacement. We measure the temperature evolution of the fault surface at the acquisition rate of 1 kHz and over a spatial resolution of ~40 µm<sup></sup>with optical fibers conveying the infrared radiation to a two-color pyrometer. Temperatures up to 1250 °C and low coseismic fault shear strength are compatible with the activation of grain size dependent viscous creep.</p>

Pore-fluid pressures and frictional heating on a fault surface

1985 ◽  
Vol 122 (2-4) ◽  
pp. 583-607 ◽  
Author(s):  
Charles W. Mase ◽  
Leslie Smith
Keyword(s):  
Frictional Heating ◽  
Pore Fluid ◽  
Fault Surface

Temperature measurements in the core of active optical fibers under lasing conditions

2010 ◽  
Vol 53 (6) ◽  
pp. 853-859 ◽  
Author(s):  
V. V. Gainov ◽  
R. I. Shaidullin ◽  
O. A. Ryabushkin
Keyword(s):  
Optical Fibers ◽  
Temperature Measurements ◽  
The Core

Surface Temperatures in Sliding Systems—A Finite Element Analysis

1981 ◽  
Vol 103 (1) ◽  
pp. 90-96 ◽  
Author(s):  
F. E. Kennedy
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Frictional Heating ◽  
Temperature Measurements ◽  
Experimental Temperature ◽  
Element Analysis ◽  
Material Parameters ◽  
Surface Temperatures ◽  
Good Agreement

Finite element equations are developed for studying surface temperatures resulting from frictional heating in sliding systems. The equations include the effect of velocity of moving components, an effect which is found to be quite significant, even at low sliding velocities. A program was written using the equations and it was applied to the study of surface temperatures in two different sliding systems: dry or boundary lubricated sleeve bearings and a labyrinth gas path seal configuration. Very good agreement was achieved between analytical predictions using the program and experimental temperature measurements. The program was used to study the influence of various material parameters on surface temperatures in the two sliding systems.

The role of heterogeneity in fault zone weakening and stability

2020 ◽  
Author(s):  
John Bedford ◽  
Daniel Faulkner ◽  
Nadia Lapusta
Keyword(s):  
Friction Coefficient ◽  
Shear Bands ◽  
Fault Gouge ◽  
Stress Concentrations ◽  
Plate Interface ◽  
Stick Slip ◽  
Fine Grained ◽  
Total Displacement ◽  
Fault Strength ◽  
Frictional Strength

<p>Heterogeneity is abundant in crustal fault zones from the micron-scale to the plate interface scale. Despite this, it is still uncertain how different scales of heterogeneity interact and influence the mechanical properties of natural faults. Here we present experimental results where heterogeneous faults are simulated in the laboratory by placing patches of different fault gouge materials next to each other in a direct shear arrangement. These laterally heterogeneous experimental faults (50 mm in total length) are then sheared and the frictional strength evolution is measured with increasing displacement. Two types of fault gouge are used: (1) a fine-grained quartz gouge which obeys Byerlee friction (coefficient of friction = 0.6-0.7) and is rate weakening, and (2) a clay gouge comprised predominantly of kaolinite which has a low friction coefficient (approx. 0.25) and is rate strengthening. We find that with the addition of only a small amount of clay gouge the bulk fault strength weakens considerably after only a few millimetres of slip. Although clay is preferentially smeared along localized Y-shear bands, the observed weakening cannot be explained by clay smear as the total displacement on the fault is far too small for the clay to be smeared through the entire length of the quartz patches. Instead we propose stress concentrations at the boundary between clay and quartz patches, driven by slip on the weaker clay patch, produce enhanced weakening and shear at an overall low stress within the quartz patches.</p><p>The scale of heterogeneity also controls the frictional stability of the experimental fault. When clay patches are small and comprise <20% of the total fault area, instabilities occur within the unstable quartz gouge leading to stick-slip behaviour. However when patches of clay comprise >20% of the total sliding area, instabilities within the quartz are supressed leading to stable sliding. In this case, the bulk fault also becomes increasingly rate-strengthening with slip, tending towards the behaviour of a fault comprised of 100% clay. These results demonstrate how natural geological heterogeneity and the interplay between different geologic materials can help explain fault weakness and also control the seismogenic potential of tectonic faults.</p>

scholarly journals Frictional heating in a thick fault zone with empirical slip-weakening friction: implications for slip parameter estimation from temperature observations in deep fault drilling

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Shunya Kaneki
Keyword(s):  
Shear Stress ◽  
Analytical Solution ◽  
Heat Source ◽  
Fault Zone ◽  
Frictional Heating ◽  
Temperature Measurements ◽  
Heat Diffusion ◽  
Deep Fault ◽  
Temperature Anomalies ◽  
Temperature Observations

AbstractThe strain energy released during an earthquake is consumed by processes related to seismic radiation or dissipation. Deep fault drilling and subsequent temperature measurements in a thick fault zone immediately after an event have provided important insights into this dissipation process. By employing an analytical solution to the heat conduction problem, which involves the sudden injection of an infinitesimally thin heat source into an infinite medium, previous drilling projects have estimated the strength of the heat source and the level of shear stress from observed temperature anomalies. However, it is unclear under what conditions this analytical source solution can be regarded as a good approximation for the thick fault problem, a situation which has led to uncertainty of the approximation error in these previous studies. In this study, I first derived an analytical solution for the thick fault problem that accounted for experimentally derived slip-weakening friction. I then validated the derived solution both analytically and numerically. Using the derived thick solution, I next demonstrated that the thick, planar, and source solutions can be considered equivalent under the typical conditions of the previous drilling projects. Therefore, the slip parameters estimated by using the source solution obtained by these studies are appropriate. These results suggest that coseismic information with spatio-temporal extent, such as shear stress and friction coefficient, are lost due to heat diffusion when the temperature observations are conducted; thus, they cannot be inferred directly from observed temperature anomalies. These results also suggest that for most drilling projects, including future ones, the observed temperature distribution can be well explained by using the source solution instead of the thick solution as long as coseismic slip is not markedly delocalized and the spatial extent of the temperature measurements is not significantly larger than the diffusion length.

Combined strain and temperature measurements using optical fibers

1995 ◽  
Author(s):  
W. Craig Michie ◽  
Brian Culshaw ◽  
Maria Konstantaki ◽  
Graham Thursby
Keyword(s):  
Optical Fibers ◽  
Temperature Measurements
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