Effect of Pressure Rate on Rate and State Frictional Slip

• Published in: Geophysical research letters 2020-11, Vol.47 (21), p.n/a
• Main Authors: Rudnicki, J. W., Zhan, Y.
• Format: Article
• Language: English
• Subjects: Earthquakes; failure; Fluid injection; Fluid pressure; Friction; Friction resistance; Frictional slip; instability; Laboratories; Laboratory experiments; Pore pressure; Pressure; Pressure dependence; Pressure effects; pressure rate; rate and state; Reservoirs; Seismic activity; Sliding; Slumping; Spring
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL089426

This paper analyzes the effects of pore pressure rate for a spring‐block system that is a simple model of a laboratory experiment. Pore pressure is increased at a constant rate in a remote reservoir, and slip is governed by rate and state friction. The frequency of rapid slip events increases with the increase of a nondimensional pressure rate that is the ratio of the time scale of frictional sliding to that for pressure increase. As the pressure rate increases, the more rapid increase of pore pressure on the slip surface quickly stabilizes slip events due to rate and state friction. Rate and state and pressure rate effects interact in a limited range of pressure rate and diffusivity. This range includes pressure rates and diffusivities representative of recent laboratory experiments. Plain Language Summary Recent field observations have identified fluid injection as an important factor in causing the dramatic increase of earthquakes in the central United States, and recent laboratory experiments have observed effects of fluid pressure rate on frictional sliding. This paper studies a simple model of a laboratory experiment: a block resting on a frictional surface and pulled by a spring. The frictional resistance to sliding depends on the rate and history of sliding. Fluid pressure is increased at a constant rate at a distance remote from the surface. The paper calculates the types and characteristics of rapid slip events and their dependence on the pressure rate and how fast fluid can diffuse from the reservoir to the frictional surface. Key Points Rapid slip events occur during the duration of a representative experiment in a limited range of pressure rate and diffusivity Above a certain pressure rate slip events are strongly damped by a rapid decrease of effective stress Interaction between fluid diffusion and pressure rate affects the type, frequency, and magnitude of slip events