Modeling Aseismic and Seismic Slip Induced by Fluid Injection on Pre-existing Faults Governed by Rate-and-state Friction

Abstract:

Pore fluid pressure evolution on pre-existing faults in the vicinity of fluid injection activity has been postulated as a key factor for inducing both moderate size earthquakes and aseismic slip. In this study, we develop a numerical model incorporating rate-and-state friction properties to investigate fault slip initiated by various perturbations, including fluid injection and transient dynamic stress changes. In the framework of rate-and-state friction, external stress perturbations and their spatiotemporal variation can be coupled to fault frictional strength evolution in a single computational procedure. Hence it provides a quantitative understanding of the source processes (i.e., slip rate, rupture area, triggering threshold) of a spectrum of slip modes under the influence of anthropogenic and natural perturbations. Preliminary results show both the peak and cumulative Coulomb stress change values can affect the transition from aseismic to seismic slip and the amount of slip.

We plan to apply the physics-based slip model to induced earthquakes in western Canada sedimentary basins. In particular, we will focus on the Fox Creek sequences in north Alberta, where two earthquakes of M_L4.4 (2015/01/23) and M_w4.6 (2015/06/13) were potentially induced by nearby hydraulic fracturing activity. The geometry of the seismogenic faults of the two events will be constrained by relocated seismicity as well as their focal mechanism solutions. Rate-and-state friction parameters and ambient stress conditions will be constrained by identifying dynamic triggering criteria using a matched-filter approach. A poroelastic model will be used to estimate the pore pressure history resolved onto the fault plane due to fluid injection. By comparing modeled earthquake source parameters to those estimated from seismic analysis, we aim to quantitatively discern the nucleation conditions of injection-induced versus dynamically triggered earthquakes, and aseismic versus seismic slip modes.