The stress- and fluid-pressure-driven frictional slip data for variably roughened fractures in Gonghe granite

We explore the impacts of stress- and fluid-pressure-driven frictional
slip on variably roughened fractures in Gonghe granite (Qinghai province,
China). Slip is on an inclined fracture under simple triaxial stresses
with concurrent fluid throughflow allowing fault permeability to be
measured both pre- and post-reactivation. Under stress-drive, smooth
faults are first slip-weakening and transition to slip-strengthening with
rough faults slip-strengthening, alone. A friction criterion accommodating
a change in friction coefficient and fault angle is able to fit the data
of stable-slip and stick-slip. Under fluid-pressure-drive, excess pore
pressures must be significantly larger than average pore pressures
suggested by the stress-drive-derived failure criterion. This overpressure
is conditioned by the heterogeneity of the pore pressure distribution in
radial flow on the fault and related to the change in permeability. Fault
roughness impacts both the coefficient of friction and the permeability
and therefore exerts important controls in fluid-injection-induced
earthquakes. The results potentially improve our ability to assess and
mitigate the risk of injection-induced earthquakes in EGS.