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

Abstract

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.