Fast and Localized Temperature Measurements During Simulated Earthquakes in Carbonate Rocks

Abstract

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 measured the temperature evolution of the fault surface at the acquisition rate of 1 kHz and over a spatial resolution of ∼40 µm with an optical fiber conveying the infrared radiation to a two‐color pyrometer. Temperatures up to 1,250°C and low coseismic fault shear strength are compatible with the activation of grain size dependent viscous creep.

Fault Friction During Simulated Seismic Slip Pulses

“…It is also important to consider that if flash processes occur during initial fault weakening, temperature may be locally higher than predicted from GSS models. An initial flux of heat resulting from asperity‐scale processes may be sustained throughout the test duration (Aretusini et al., 2021), which would allow larger grain sizes to give quantitative agreement with the experimental data. We also note that in Violay et al.…”

Determination of Parameters Characteristic of Dynamic Weakening Mechanisms During Seismic Faulting in Cohesive Rocks

“…For the flash temperature, various percentages of the real contact area were taken into consideration. (a) Measured temperature (black line) with 5% error on the measurements (gray area) (Aretusini, Núñez‐Cascajero, et al., 2021) for the entire experiments compared with the diffusion bulk temperature used for the diffusion creep model only (green line). (b) Zoom on the first 0.4 m of slip.…”

“… Temperature evolution for experiment s1684: measured temperature with optical fibers (black line, Aretusini, Núñez‐Cascajero, et al., 2021) compared with the estimated temperature for flash heating and diffusion creep model (green line). For the flash temperature, various percentages of the real contact area were taken into consideration.…”

“…In the case of calcitic marble, optical fibers were used to measure the temperature at high spatial (ca. 20 μm) and temporal (1 kHz) resolution in the slipping zone (Aretusini, Núñez‐Cascajero, et al., 2021). This new data set allowed us to discuss temperature estimates and the thermal control of the transition from flash heating to bulk‐scale weakening processes (diffusion creep in that case).…”

“…Flash heating and bulk melting are investigated for silicate‐built rocks, while flash heating and dislocation creep or flash heating and diffusion creep are investigated for calcite‐built rocks. Furthermore, we present a novel way to model and interpret the measured temperature at high acquisition rates with optical fibers inside the slipping zone (Aretusini, Núñez‐Cascajero, et al., 2021). This approach helps to validate the assumptions made when modeling temperature from the mechanical data and interpret the possible contribution to the temperature rise of the investigated weakening mechanism.…”