Transition From Slow to Fast Injection‐Induced Slip of an Experimental Fault in Granite Promoted by Elevated Temperature

The influence of elevated temperature on injection‐induced fault slip is poorly constrained. In this study, at steady‐state elevated temperatures, triaxial shear‐flow experiments on a sawcut fault in granite were conducted to simulate injection‐induced slip of a critically stressed fault. Our results suggest that an elevated temperature favors a more uniform fluid pressure distribution over the fault surface mainly by reducing water viscosity. At temperatures above ambient, a larger perturbation force from the injected fluid is required to reactivate the fault primarily because of the enhanced thermally activated fault healing processes, resulting in a faster fault slip rate upon failure. This study may partially explain the causal link between higher reservoir temperature and higher maximum magnitude of injection‐induced earthquakes in geothermal systems, and the observation that larger magnitude seismic events concentrate near the deeper part of the reservoir, where temperature is higher.