Healing and frictional behavior of the southern San Andreas fault reveals ability to host shallow slow slip events

Alexandra A. DiMonte, Alexis K. Ault, Srisharan Shreedharan, & Greg Hirth

Under Review October 30, 2024, SCEC Contribution #14092

The southern San Andreas fault is in its interseismic period, occasionally releasing some stored elastic strain during shallow slow slip events. Shallowly-exhumed, compositionally heterogeneous, clay-rich fault gouge defines the fault. To evaluate the influence of this material on shallow slip behavior, we characterize its frictional and healing properties with deformation experiments at room temperature, 10 MPa effective stress, and load rates <5 μm/s, and compare healing rates to natural slow slip events. Together with X-ray diffraction and microscopy, our results show the gouge is weak (coefficient of friction of 0.25-0.30 when water-saturated), exhibits a near-zero healing rate, and transitions from unstable to a stable behavior at slip rates above ~1 μm/s. Collective observations indicate clay influences the behavior of the southern San Andreas fault. At depth, the gouge could promote the nucleation of geodetically-observed shallow slow slip events and/or localize slip that facilitates earthquake rupture propagation to the surface.

Citation
DiMonte, A. A., Ault, A. K., Shreedharan, S., & Hirth, G. (2024). Healing and frictional behavior of the southern San Andreas fault reveals ability to host shallow slow slip events. Geophysical Research Letters, (under review).

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