Abstract
Fault-zone fluids control effective normal stress and fault strength. While most earthquake models assume a fixed pore fluid pressure distribution, geologists have documented fault valving behavior, that is, cyclic changes in pressure and unsteady fluid migration along faults. Here we quantify fault valving through 2-D antiplane shear simulations of earthquake sequences on a strike-slip fault with rate-and-state friction, upward Darcy flow along a permeable fault zone, and permeability evolution. Fluid overpressure develops during the interseismic period, when healing/sealing reduces fault permeability, and is released after earthquakes enhance permeability. Coupling between fluid flow, permeability and pressure evolution, and slip produces fluid-driven aseismic slip near the base of the seismogenic zone and earthquake swarms within the seismogenic zone, as ascending fluids pressurize and weaken the fault. This model might explain observations of late interseismic fault unlocking, slow slip and creep transients, swarm seismicity, and rapid pressure/stress transmission in induced seismicity sequences.
Highlights
Fault-zone fluids control effective normal stress and fault strength
We test the viability of fault valving and explore phenomena that arise from the coupling between fluids and faulting processes. This is done in an earthquake sequence model that accounts for the coupling between fault zone fluid flow, pore pressure and permeability evolution, and elastic stress transfer from fault slip
The purpose of this study is to introduce a quantitative simulation framework in which to explore the two-way coupling between fluid transport, pore pressure evolution, and fault slip over the earthquake cycle
Summary
Fault-zone fluids control effective normal stress and fault strength. While most earthquake models assume a fixed pore fluid pressure distribution, geologists have documented fault valving behavior, that is, cyclic changes in pressure and unsteady fluid migration along faults. The intermittency of fluid pressurization and release, a concept known as fault valving[30,31], is a consequence of feedback between fault slip and deformation, which typically elevate permeability[32,33,34], and healing and sealing processes, like pressure solution transfer, that reduce permeability[35,36,37,38,39] These feedback effects are amplified by nonlinear dependence of permeability on effective normal stress due to mechanical compression of pores and microfractures[13,19,40]. The model predicts the spontaneous generation of fluid-driven aseismic slip and overpressure pulses near the base of the seismogenic zone and earthquake swarms within the seismogenic zone, as ascending fluids pressurize and weaken the fault These phenomena might explain many related observations, such as late interseismic fault unlocking, slow slip, swarm seismicity, and rapid pressure transmission along faults in induced seismicity sequences
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
