EGU2020-16538
https://doi.org/10.5194/egusphere-egu2020-16538
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Exploring frictional velocity dependence as a mechanism for slow earthquake rupture

Julia Krogh and Chris Marone
Julia Krogh and Chris Marone
  • Department of Geosciences, Pennsylvania State University, University Park, PA, USA

Earthquakes fail through a spectrum of slip modes ranging from slow slip to fast elastodynamic rupture. Slow earthquakes, or slow-slip events, represent fault slip behaviors that involve quasi-dynamic, self-sustained rupture propagation. To better understand the mechanisms that limit the slip speed and propagation rates of slow slip, we focus on a particular parameter: the critical frictional weakening rate of the fault surface, kc. When kc is approximately equal to k, the elastic loading stiffness of the fault, complex fault slip behaviors including slow-slip events are observed. If kc has a negative dependence on slip velocity, acceleration during the coseismic phase could decrease kc until it approximates k, terminating in a slow earthquake. Here, we describe the results of laboratory experiments designed to quantify the dependence of kc on frictional slip velocity. We conducted double-direct shear experiments in a biaxial shearing apparatus with 3 mm-thick fault zones composed of quartz powder to simulate fault gouge. We focus on step decreases in slip velocity from 300 to 3 m/s that were performed for a range of normal stresses, from 10 to 20 MPa, which we know to be near the stability transition from stable to unstable sliding defined by k/kc ~ 1.0. Under stable conditions, rate-state friction modeling was used to determine kc for each velocity step. Our data provide direct insight on the stability transition associated with kc(V), including experiments for which slow-slip instabilities grew larger and faster throughout velocity-step sequences. Ultimately, both numerical modeling and observational data indicate that the velocity dependence of kc is an important parameter when considering the mechanisms of slow earthquake nucleation. 

How to cite: Krogh, J. and Marone, C.: Exploring frictional velocity dependence as a mechanism for slow earthquake rupture, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16538, https://doi.org/10.5194/egusphere-egu2020-16538, 2020

This abstract will not be presented.