Earthquakes as a coupled shear stress‐high pore pressure dynamical system

Abstract

The migration, coalescence and localization of slip, seismicity, and zones of high pore pressure are modeled using a porosity reduction mechanism to drive pore pressure within a fault zone in excess of hydrostatic. Increased pore pressure in discrete cells creates zones of low effective stress, which induces slip that may propagate to surrounding cells depending on the local state of stress. At slip, stress is transferred using the solution for a rectangular dislocation in an elastic half‐space, and pore pressures are redistributed by conserving fluid mass. Using simple assumptions about fault rheology and permeability, it is shown that the interaction between shear stress and effective stress evolves to a state of earthquake clustering with repeated events, locked zones, and large variations in fault strength. The model evolves from a uniform shear stress state on a strong fault, to a heterogeneous shear stress state on a weak fault.

Introduction to Special Section: Stress Triggers, Stress Shadows, and Implications for Seismic Hazard

“…This is similar to many of the models currently in use: they determine where nucleation could occur, but do not a priori place a limit on the extent of rupture (magnitude), except as a statistical phenomenon [e.g., Dieterich, 1994]. One type of quasi-static model that does look at the potential maximum magnitude is that of Miller et al [1996]. In the Miller et al [1996] hypothesis the effect of a nearby earthquake reducing the normal stress on a fault is to delay a large earthquake from occurring, whereas small earthquakes could still occur.…”

Different styles of faulting deformation along the Dead Sea Transform and possible consequences for the recurrence of major earthquakes

“…Recent models of fault evolution propose a cyclic nature of earthquake faulting processes where faults act as seals during seismic quiescence and as conduit during earthquakes (e.g. Sibson, 1992;Rice, 1992;Sleep and Blanpied, 1992;Caine et al, 1996;Miller et al, 1996;Miller, 2002). The basic assumption is that pore pressure increases within the fault zone during tectonic loading and decreases during faulting.…”

A fluid‐rock interaction cellular automaton of volcano mechanics: Application to the Piton de la Fournaise

“…We just note that the power law exponent is generally a bit lower than that observed on the data. Such correlation in terms of frequency-size statistics between the simulated fluid flow avalanches and the real seismicity reinforces the presumptions for a coupling between the dynamics of fluid flow and induced seismicity processes [Byeflee, 1993;Miller et al, 1996].…”

“…In such a context, the good correlation between the PF Gutenberg-Richter distribution of earthquakes and the simulated size distribution of endogenous avalanches (Figure 8) is not a surprising result. This model provides a framework to understand the hierarchical organization of seismicity that is reported on most volcanoes [Grasso et al, 1994] and further argues for a coupling between fluid transfers and fluid-induced seismicity, elsewhere proposed for fault mechanics [Miller et al, 1996] or gas reservoir depletion [Grasso, 1993]. We thus have evidence for a rare universal process in terms of implied scales, allowed by the fact that the model control parameter (i.e., the fluid pressure) does not need to be re-normalized at each scale.…”