Elevated temperatures promote frictional instability in kaolinite-quartz fault gouges
Year: 2025
Type: article
Abstract: Large earthquakes nucleate on crustal faults that have accumulated significant slip displacement, and field observations show that these faults are ubiquitously rich in clay minerals. Earthquake nucleation and propagation requires a reduction in shear resistance for instability to develop and then to continue. Room temperature laboratory friction measurements indicate that only stable fault creep should typically occur in clay-rich faults; a result at odds with observations of widespread earthquake behaviour on mature faults in nature. A suite of frictional velocity step experiments was designed to test the notion that temperature may reduce the stability of clay-rich faults, measured by the friction parameter ( a-b ), up to 180 °C. The stability of synthetic kaolinite clay-bearing fault gouges was found to decrease systematically with elevated temperatures commensurate with those found at typical earthquake depths, at an effective pressure of 90 MPa. In materials containing 25–50 % clay, the stability of slip decreased with increasing temperature so that the gouges displayed unstable slip at temperatures between 100 and 180 °C. At room temperature the same materials showed stable slip and velocity strengthening characteristics. The reduction in stability with increasing temperature coincides with a greater degree of shear localization observed in the gouge microstructure and is hypothesized to result from progressive loss of water adsorbed on the clay surfaces. These results indicate that clay-bearing fault rocks can nucleate unstable slip at conditions common to the clay-bearing brittle crust – an outcome in line with the observation that mature clay-bearing faults in nature can nucleate and propagate earthquakes.
Institution: University of Liverpool
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,670
OpenAlex ID: W7090860467