Multimechanism friction constitutive model for ultrafine quartz gouge at hypocentral conditions

Abstract

Occurrence of instability in crustal faults depends in part on the small-magnitude dependence of frictional strength on slip rate and slip history. Rate dependence of friction reflects the operation of thermally activated mechanisms at points of contact along fault surfaces and is expected to change in space and time owing to variations in environmental conditions and slip rams during the seismic cycle. Several lines of evidence suggest solution-precipitation processes in fault zones may be activated during interseismic periods when slip rates are small and may contribute to fault healing. We develop a constitutive model for faulting at hypocentral conditions that is capable of describing the variation in frictional properties as different slip mechanisms are activated in response to changes in temperature or slip rate. This model is based on the assumption that slip mechanisms are thermally activated and follow an Arrhenius relationship between temperature and slip rate, which allows the addition of temperature dependence to existing rate-and state-dependent friction constitutive laws. Multiple slip mechanisms are treated as operating independently and concurrently, where each mechanism is described by the rate-, state-, and temperature-dependent friction constitutive relation. The constitutive model is used to analyze tdaxial friction experiments on ultrafine-grained quartz gouge at temperatures to 600øC, effective confining pressure of 150 MPa, and water-saturated or room-dry conditions. These experiments investigated the stress relaxation response and slip history effects during slide-hold-slide tests with hold times up to 105 s. The microstructure of the deformed quartz gouge and the transient friction behavior define at least two distinct frictional slip regimes: a low-temperature regime characterized by cataclastic mechanisms with significant slip history effects, and a high-temperature regime characterized by solution-precipitation-aided cataclastic flow with large-magnitude rate dependence and insignificant slip history effects. In the model the parameters of the friction constitutive relation (e.g., a, b, and L) are treated as constants for each slip mechanism but are different for the different mechanisms. This model accurately describes the frictional behavior within each regime and across the transition between regimes. The analysis suggests that the greatest-magnitude rate weakening behavior occurs at 100 ø to 300øC under wet conditions at laboratory slip rates. Significant solution-precipitation is activated at temperatures above 300øC at laboratory slip rates or at lower slip-rates and lower temperatures. The high-temperature solution-precipitation regime is described by a large-magnitude rate strengthening (a -b = 0.03) and an apparent activation energy of ap-kJ moF . The constitutive analysis suggests that the solution-precipitation-aided flow mecha-proximately 44 nism could be important during interseismic periods at hypocentral conditions and low shear stress but apparently is not characterize...

Quantitative measure of the variation in fault rheology due to fluid‐rock interactions

“…The rates of those thermally activated mechanisms vary with temperature through an Arrhenius relation, and it is reasonable to speculate that the value of a constitutive parameter varies linearly with inverse temperature within the conditions of dominance of a given deformation mechanism. Similar, though mathematically distinct, reasoning was earlier employed by Chester [ 1988Chester [ , 1994 and Chester and Higgs [1992], who developed a temperaturedependent constitutive law by adding Arrhenius-like terms to Ruina's equations for friction (2) and the evolution of state (3), using a single state variable. We have highlighted trends in Figure 7 by piecewise linear regression to the mean values for wet gouge.…”

“…Blanpied et al [1991,1995] inferred that one or more unspecified fluid-activated deformation processes were active in this second regime. Shearing tests on quartzite powder at hydrothermal conditions, accompanied by microstructural evidence [Higgs, 1981;Chester and Higgs, 1992], show that solution-transport of silica can accompany cataclasis at conditions similar to those in the second, hydrothermal, regime. Thus solution-transport creep in quartz is one candidate mechanism to explain the reduced strength at hydrothermal conditions.…”

Effects of slip, slip rate, and shear heating on the friction of granite

“…It has been shown for quartz and granite that changes in temperature affect the frictional strength, the velocity dependence of friction, and the stability of sliding [Stesky, 1978;Lockner et al, 1986;Chester and Higgs, 1992;Chester, 1994;Btanpied et at., 1991Btanpied et at., , 1995. For dry rocks, and for temperatures below about 300øC, the dependence of friction on temperature is slight and can be of either sign.…”

Multistable slip of a one-degree-of-freedom spring-slider model in the presence of thermal-pressurized slip-weakening friction and viscosity

“…When fluids are present and temperature changes in faults, thermal pressurization will yield resistance on the fault plane and thus play a significant role in earthquake rupture (Sibson, 1973;Lachenbruch, 1980;Chester and Higgs, 1992;Fialko, 2004;Fialko and Khzan, 2005;Bizzari and Cocco, 2006a, b;Rice, 2006;Wang, 2000Wang, , 2006Wang, , 2009Wang, , 2011Wang, , 2013Wang, , 2016bWang, , 2017Bizzarri, 2010Bizzarri, , 2011a. Rice (2006) proposed two end-member models for thermal pressurization: the adiabatic-undrained-deformation (AUD) model and the slip-on-a-plane (SOP) model.…”