Understanding rate effects in injection-induced earthquakes.

Area of Science:

• Geophysics
• Earthquake Science
• Subsurface Engineering

Background:

• Understanding the physical mechanisms linking fluid injection and seismicity is crucial for managing seismic risk in subsurface technologies.
• Poroelastic models are key to analyzing earthquake nucleation and frictional instability.

Purpose of the Study:

• To develop a poroelastic model of earthquake nucleation based on rate-and-state friction.
• To analyze conditions for stick-slip frictional instability using linear stability analysis and nonlinear simulations.

Main Methods:

• Development of a poroelastic model incorporating rate-and-state friction.
• Linear stability analysis to determine conditions for instability.
• Nonlinear simulations to observe system dynamics.

Main Results:

• The likelihood of triggering earthquakes is primarily dependent on the rate of pore pressure increase, not its magnitude.
• Constant-rate fluid injection initially promotes seismic rupture, followed by aseismic creep.
• Abrupt high-rate injection protocols increase seismic risk compared to gradual step-up protocols for the same fluid volume.

Conclusions:

• Pore pressure increase rate is a critical factor in fluid-induced seismicity.
• Injection protocols significantly impact seismic risk; gradual increases are safer.
• Model findings offer insights for mitigating seismic hazards associated with fluid injection.