On the possibility of earthquake rupture through clay-rich faults

Daniel Faulkner, Marieke Rempe, John Bedford, C Sanchez-Roa, C Boulton, & S den Hartog

Submitted August 17, 2018, SCEC Contribution #8840, 2018 SCEC Annual Meeting Talk on Tue 08:30

Many mature, large-displacement fault zones exhibit a clay-rich fault core. This low porosity, low permeability material inhibits the migration of fluid and consequently small changes in porosity produce pore pressure transients that take significant time to dissipate. Despite most clay-rich fault gouges displaying velocity strengthening frictional characteristics, variations in pore-fluid pressure can result in a wide range of behaviour including apparent velocity weakening leading to possibility of these rocks hosting instabilities. We present laboratory constraints of the frictional properties of clay-rich fault gouge both at low slip velocity, commensurate with earthquake nucleation and at higher slip velocity, equivalent to that during rupture propagation. We show that small amounts of compaction can result in large strength changes and apparent velocity weakening behaviour at slow slip velocity. At higher slip velocity, experimental results suggest thermal pressurization in clay-rich fault gouge is an efficient process that produces weakening over small slip displacements. Accounting for pore-fluid pressure effects during slip predicts a wide variety of behaviour including enhanced fault creep, slip transients, and even the possibility of rupture propagation on clay-rich fault zones.

Citation
Faulkner, D., Rempe, M., Bedford, J., Sanchez-Roa, C., Boulton, C., & den Hartog, S. (2018, 08). On the possibility of earthquake rupture through clay-rich faults. Oral Presentation at 2018 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)