Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip

Abstract

Fluids influence fault zone strength and the occurrence of earthquakes, slow slip events, and aseismic slip. We introduce an earthquake sequence model with fault zone fluid transport, accounting for elastic, viscous, and plastic porosity evolution, with permeability having a power-law dependence on porosity. Fluids, sourced at a constant rate below the seismogenic zone, ascend along the fault. While the modeling is done for a vertical strike-slip fault with 2D antiplane shear deformation, the general behavior and processes are anticipated to apply also to subduction zones. The model produces large earthquakes in the seismogenic zone, whose recurrence interval is controlled in part by compaction-driven pressurization and weakening. The model also produces a complex sequence of slow slip events (SSEs) beneath the seismogenic zone. The SSEs are initiated by compaction-driven pressurization and weakening and stalled by dilatant suctions. Modeled SSE sequences include long-term events lasting from a few months to years and very rapid short-term events lasting for only a few days; slip is ˜1-10 cm. Despite ˜1-10 MPa pore pressure changes, porosity and permeability changes are small and hence fluid flux is relatively constant except in the immediate vicinity of slip fronts. This contrasts with alternative fault valving models that feature much larger changes in permeability from the evolution of pore connectivity. Our model demonstrates the important role that compaction and dilatancy have on fluid pressure and fault slip, with possible relevance to slow slip events in subduction zones and elsewhere.

Linking 3D Long‐Term Slow‐Slip Cycle Models With Rupture Dynamics: The Nucleation of the 2014 Mw 7.3 Guerrero, Mexico Earthquake

“…Future work may explore the additional effects of dilatancy that may stabilize co‐seismic slip (Segall et al., 2010) and may affect the overall slip budget at the downdip limit of the seismogenic zone (Y. Liu & Rubin, 2010; Y. J. Liu, 2013). The effects of dilatancy and permeability enhancement in highly permeable fault zones may alter aseismic slip (Yang & Dunham, 2023). Dal Zillo et al., 2020 consider dilatancy to model SSEs in a planar Cascadia model and find slightly slower down‐dip rupture speed and longer event durations, which may affect megathrust earthquake nucleation.…”

“…By coupling porosity and permeability evolution to elastic fault deformation, Yang and Dunham (2023) demonstrate the potentially critical role of pore fluid transportation and permeability evolution on slow slip and seismic cycles in a 2D antiplane fault model. Using a two‐phase flow model that couples solid rock deformation and pervasive fluid flow, dal Zilio et al.…”

“…Integrated modeling of long‐term tectonic loading and coseismic rupture advances the understanding of the dynamics of interseismic and coseismic slip, as well as their interplay (Cattania, 2019; Kaneko et al., 2011; Liu et al., 2020). While a few implementations have been developed to integrate long‐term slow interseismic loading and fast coseismic rupture (Cattania & Segall, 2021; Segall et al., 2010; Yang & Dunham, 2023), they typically omit inertia effects during the interseismic period. Liu et al.…”