Modeling fluid transfer along California faults when integrating pressure solution crack sealing and compaction processes

Abstract

[1] Several models pertaining to earthquake cycles imply intermittent fluid flow through fault. During the interseismic period, increase in fluid pressure from hydrostatic to lithostatic values is a crucial parameter in mechanisms leading to earthquakes. To achieve such pressures, geodynamic processes (gouge compaction, fluid flow) and changes in permeability are required. Previous models have postulated that changes in permeability (by self-healing) are faster than the effects of geodynamic processes. We consider the different mechanisms and rates of crack sealing near active fault on the examples of uplifted Californian faults. We find that natural crack sealing is normally not achieved by a rapid self-healing process. Pressure solution, with mass transfer from solution cleavage to cracks, appears to be a more important mechanism for crack sealing and creep during postseismic deformation. The geometry of transfer path and experimental data have been used to model crack sealing rates by pressure solution which are estimated to be rather slow, similar to the recurrence time of some earthquakes. Such slow changes in permeability may be crucial factors in controlling the increase in fluid pressure and, consequently, the mechanism of critical failure in faults. Then, numerical modeling of fluid pressure and transfer around active faults has been performed integrating a slow change in permeability by crack sealing, gouge compaction, and fluid flow from depth. This modeling shows various location and evolution of fluid overpressure during the interseismic period depending on these processes and allows one to estimate the amount of fluid transferred from depth during interseismic periods.

Compaction creep of wet granular calcite by pressure solution at 28°C to 150°C

“…Such microstructures are widely found in carbonate and sandstone rocks, often in association with evidence for grain scale microfracturing and cracking healing [Renard et al, 2000, Gratier et al, 2003. However, evidence for IPS and localized zones of pressure solution, such as stylolites, is perhaps most common in carbonate rocks [Bathurst, 1958;Tada and Siever, 1989;Renard et al, 2004].…”

“…In seismogenic fault zones, ongoing compaction by IPS may lead to the formation of sealed compartments in which the pore fluid pressure increases until fault rupture recurs, thus controlling the seismic cycle [Caine et al, 1996;Renard et al, 2000. Similarly, the compaction of basin sediments and gouge-filled fault zones by IPS can determine the evolution of fluid pressure and fluid flow on the basin scale [Miller et al, 1999;Yang, 2000;Gratier et al, 2003;Tuncay and Ortoleva, 2004].…”

Isotopic evidence for the infiltration of mantle and metamorphic CO2–H2O fluids from below in faulted rocks from the San Andreas Fault system

“…As we draw our conclusions from rocks sampled at the surface along the trace of the SAF, we cannot infer if the identified fluid pathways correspond with the seismically defined fault plane. Most likely, fluid channeling corresponded with highdeformation zones, including pressure solution and crack filling (Pili et al, 2002;Gratier et al, 2003), which may be more active during interseismic intervals rather than during earthquakes.…”

“…Faulkner and Rutter (2001) estimated that the flux over time of only mantle-derived CO 2 and water produced from dehydration reactions appears inadequate. A crustal source of fluid and matter has been taken into account by Gratier et al (2003) who integrated crack sealing by pressure solution and compaction processes. Fulton and Saffer (2009) evaluated the role of water derived from dehydration of a serpentinized mantle wedge in weakening the SAF but neglected CO 2 influx.…”

“…Veins developed as fractures during earthquakes or during the related interseismic deformation since their orientation are consistent with neighboring fault displacements. A comprehensive study of the geochemical and structural relationships between veins, gouges and host rocks is given by Pili et al (2002) and is modeled by Gratier et al (2003). We systematically sampled deformation zones, veins and host rocks across and along fault zones, with centimeter-to kilometer-scale profiles.…”