Seismic Cycles 6 - Fluids and Poroelasticity
Earthquake cycle simulations with creep compaction and dilatancy
The goal of this study is to examine how porosity changes from dilation and compaction of the fault influence the occurrences of SSEs and earthquakes. We introduce porosity evolution encapsulating elastic, plastic and viscous deformation of the porous space, fully coupled to fault slip and pore pressure changes in a unified earthquake sequence simulation model. This is done in 2D antiplane shear for a planar, permeable rate-and-state fault in a homogeneous elastic solid. For fluid transport, we consider a mature fault zone with a well-developed damage zone. The damage zone is much more permeable than the fault core, and the modeled fault is a line, a 1D idealization of the damage zone which has a width varying from decameters to kilometers. Fluids are confined to the fault with along-fault diffusion in the damage zone. There is a constant fluid source at the bottom of the domain to approximate fluids produced from dehydration reactions of hydrous minerals. Porosity and permeability evolve with slip, with permeability related to porosity via a power-law relation. The SSEs are driven by the interaction between pore compaction which raises fluid pressure and weakens the fault, as well as pore dilation which decreases fluid pressure and limits the slip instability. We propose that the dynamics of pore compaction and dilatancy and the associated fluid pressure cycling, as well as velocity weakening friction likely have important implications for slow slip events across different tectonic settings.
Camilia Cattania, MIT
|When:||Friday 17 June, 2022, 9:00 am - 10:00 am PDT|