Rempe, M;
Di Toro, G;
Mitchell, TM;
Smith, SAF;
Hirose, T;
Renner, J;
(2020)
Influence of effective stress and pore‐fluid pressure on fault strength and slip localization in carbonate slip zones.
Journal of Geophysical Research: Solid Earth
, 125
(11)
, Article e2020JB019805. 10.1029/2020jb019805.
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Abstract
The presence of pressurized fluids influences the mechanical behaviour of faults. To test the roles of normal stress and fluid pressure on shear strength and localization behaviour of calcite gouges, we conducted a series of rotary‐shear experiments with pore‐fluid pressures up to 10.5 MPa and difference between normal stress and fluid pressure up to 11.2 MPa. Calcite gouges were sheared for displacements of 0.3 m to several meters at slip rates of 1 mm/s and 1 m/s. Drainage conditions in experiments were constrained from estimates of the hydraulic diffusivity. Gouges were found to be drained at 1 mm/s, but possibly partially undrained during sliding at 1 m/s. Shear strength obeys an effective‐stress law with an effective‐stress coefficient close to unity with a friction coefficient of c. 0.7 that decreases to 0.19 due to dynamic weakening. The degree of comminution and slip localization constrained from experimental microstructures depends on the effective normal stress. Slip localization in calcite gouges does not occur at low effective normal stress. The presence of pore fluids lowers the shear strength of gouges sheared at 1 mm/s and causes an accelerated weakening at 1 m/s compared to dry gouges, possibly due to enhanced subcritical crack growth and intergranular lubrication. Thermal pressurization occurs only after dynamic weakening when friction is generally low and relatively independent of normal stress and therefore unaffected by thermal pressurization. The experimental results are consistent with the view that the presence of pressurized fluid in carbonate‐bearing faults can facilitate earthquake nucleation.
| Type: | Article |
|---|---|
| Title: | Influence of effective stress and pore‐fluid pressure on fault strength and slip localization in carbonate slip zones |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2020jb019805 |
| Publisher version: | https://doi.org/10.1029/2020jb019805 |
| Language: | English |
| Additional information: | This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
| Keywords: | Rotary‐shear experiments, calcite gouges, seismic slip rates, strain localization, effective‐pressure law, microstructures |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10112826 |
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