CESS Seminar - Fracture Mechanics of Faults with Rate-and-State Friction: from slow to fast slip

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Event details

Date 11.11.2022
Hour 12:1513:00
Speaker Prof. Dmitry I. Garagash, Dalhousie University (Halifax, Canada)
Location
Category Conferences - Seminars
Event Language English
Abstract
Numerical simulations show that propagation of slip transients on a fault governed by rate-and-state-dependent friction resembles a fracture whose near tip region is characterized by a large stress departure from the steady-state sliding strength. This observation holds for both slow-aseismic and fast-earthquake-like slip fronts. In this work, we develop a near fracture tip solution that describes the unsteady dynamics and allows to obtain a closed-form expression for the fracture energy $G_c$, associated with overcoming strength-excursion away from the frictional steady-state, as a function of the fracture front speed $v_r$. This allows us to apply the ‘small scale yielding’ concept of fracture mechanics to model rate-state slip transients as singular cracks characterized by the simplified, steady-state frictional resistance in the bulk of the fracture, and by a stress singularity at the fracture tip defined in terms of $G_c(v_r)$ [Garagash, PTRS 2021]. As a result, we develop an analytical equation of motion to study slip driven by a combination of uniform background stress and of a localized disturbance of the fault strength characterized by the net Coulomb force $\Delta T$. The framework can be used to study and forecast run-out of aseismic and seismic slip on faults under either natural (e.g. plate tectonics) or/and anthropogenic (e.g. fluid injection) forcing. For the case of a fluid injection into the subsurface in a fault's proximity, $\Delta T$ becomes a proxy for the injected fluid volume. We show in the case of ongoing fluid injection, that the propagation speed of an aseismic fault slip transient scales with the fluid injection rate. And, once the injection is stopped, the long-term, maximum slip run-out distance on the fault scales with the square of the injected fluid volume. We show that under typical injection scenarios, aseismic slip fronts far outrun the pore pressure diffusion fronts, thus, potentially explaining the triggering of distant seismicity on hydraulically stimulated faults.

Bio
Dr. Dmitry I. Garagash is Professor of Civil and Resource Engineering at Dalhousie University in Halifax, Canada.  He received his BS and MSc in Applied Mathematics and Mechanics from Moscow State University and PhD in Geological Engineering from the University of Minnesota.  In his research, Dr. Garagash applies mechanics and physics principles to problems in  Earth and environmental sciences and geo-energy engineering. He studies hydraulic fracture propagation as pertains to the stimulation of hydrocarbon reservoirs, geological sequestration of liquid waste, and associated fault slip transients and induced seismicity. His other research interests are in the broader physics of the earthquake source, from nucleation to fully developed dynamic rupture, and the underlying constitutive behavior of fault gouge at slow and fast slip.

Practical information

  • Informed public
  • Free

Organizer

  • Prof. Alex Alahi (VITA), Prof. Olga Fink (IMOS), Prof. Dusan Licina (HOBEL) and Prof. Alain Nussbaumer (RESSLab)

Contact

  • Prof. Brice Lecampion (GEL)

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CESS

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