RSFit3000: A MATLAB GUI-Based Program for Determining Rate and State Frictional Parameters from Experimental Data

Skarbek, R. M.; Savage, H. M.

doi:10.31223/osf.io/tf32k

Cited by 18 publications

(23 citation statements)

References 25 publications

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“…(b) Zoom on a velocity step. The experimental curve is presented in black, and the model inversion using the Skarbek and Savage () software is presented in red.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Fault Reactivation During Fluid Pressure Oscillations: Transition From Stable to Unstable Slip

et al. 2019

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High-pressure fluid injection in deep georeservoirs can induce earthquakes. Recent observations suggest that cyclic injections might trigger less seismicity than monotonic injections. Here, we report triaxial laboratory experiments conducted on faulted quartz-rich sandstone that provide new insight into the physics of fault-fluid interactions subjected to cyclic fluid pressure variations. The experiments were performed at 30 and 45 MPa confining pressure, imposing constant or sinusoidal fluid pressure oscillations of amplitudes ranging from 0 to 8 MPa in addition to a far-field constant loading rate (10 −4 and 10 −3 mm s −1 ). The results show that (i) in agreement with the Mohr-Coulomb theory, faults reactivate at the static friction criterion, which is generally reached at the maximum fluid pressure during oscillations. (ii) Oscillating fluid pressure perturbations promote seismic behavior rather than aseismic slip, and (iii) increasing the oscillation's amplitude enhances the onset of seismic activity along the fault. We demonstrate that this behavior is caused by slip rate variations resulting from the fluid pressure oscillations. Without fluid pressure oscillations, increasing the far-field loading rate also promotes seismic activity. Our experiments demonstrate that the seismicity intensification due to cyclic fluid injections could be promoted at shallow depth, where confining pressure is relatively low, resulting in large strain rate perturbations.

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“…(b) Zoom on a velocity step. The experimental curve is presented in black, and the model inversion using the Skarbek and Savage () software is presented in red.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Fault Reactivation During Fluid Pressure Oscillations: Transition From Stable to Unstable Slip

et al. 2019

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“…To determine the velocity dependence of friction, data were fit with the rate‐and‐state friction relation using an iterative least squares inversion method (Reinen & Weeks, ) and the RS3000 code developed for triaxial deformation apparatus (Skarbek & Savage, ). Individual rate‐steps were de‐trended using a linear fit to the 300 μm before the rate‐step to correct for slip hardening, and the 400 μm following each rate‐step was used to model the evolution of friction.…”

Section: Methodsmentioning

confidence: 99%

“…Sample stiffness is an important parameter which controls whether velocity‐weakening materials stably slide or exhibit stick‐slip behavior (Leeman et al, ; Scuderi et al, ). Sample stiffness has been shown to evolve by > 50% during experiments due to compaction, comminution, and shear localization (Leeman et al, ; Skarbek & Savage, ). Following the suggestions of Skarbek and Savage (), we treat sample stiffness as a fitting parameter, and find that sample stiffness ranges from 5 × 10 −4 to 5 × 10 −3 μm −1 (Δμ/Δx) in our experiments (Table S1).…”

Section: Methodsmentioning

confidence: 99%

Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes

et al. 2020

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Earthquakes are expected to nucleate within velocity‐weakening materials; however, at the updip limit of the subduction seismogenic zone, the principal lithologies exhibit velocity‐strengthening behavior. At an exhumed analogue for present‐day subduction at Nankai (the Mugi Mélange, Japan) two examples of paleoseismic features occur within altered basalts, suggesting that they may be velocity‐weakening. We shear altered basalt and shale matrix from the mélange in the triaxial saw cut configuration at in situ conditions of deformation (Pc = 120 MPa, T = 150 °C) for two pore fluid factors (λ = 0.36, 0.7). The shale matrix exhibits a coefficient of friction between 0.4 and 0.5, and velocity‐strengthening behavior. Altered basalt exhibits Byerlee friction and velocity‐weakening behavior. In most experiments deformation was partitioned into Riedel shears, which have a lower percentage of clasts, clast size distributions with higher fractal dimensions, and shape factors indicating rounder clasts compared to the matrix between Riedel shears. We hypothesize that earthquakes preferentially nucleate within altered basalt at the updip limit of the seismogenic zone. More complex forms of deformation (e.g., shallow very low frequency earthquakes) may occur by mixing velocity‐weakening altered basalt into the velocity‐strengthening shale matrix. In subduction zones where the matrix is composed of shale, this complex behavior is limited to shallow depths (T < ~250 °C), above the updip transition to velocity‐weakening behavior for the matrix. Altered basalt is a ubiquitous subducting material, and future studies on its behavior through a range of subduction zone conditions are required for a full understanding of the mechanical behavior of subduction zones.

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“…

\frac{d θ_{i}}{italicdt} = 1 - \frac{V θ_{i}}{D_{italicci}}, normali = 1, 2

where a , b 1 , and b 2 are dimensionless parameters, θ 1 and θ 2 are state variables (units of time), and D c 1 and D c 2 are critical slip distances over which friction evolves to a new steady‐state value (Dieterich, 1979, 1981). In order to extract these parameters, we fit our experimental friction data with an inverse model that combines Equations 3 and 4 and an expression for system stiffness (Reinen & Weeks, 1993; Saffer & Marone, 2003; Skarbek & Savage, 2019) (Figure 2c). We employ the two state variable version of Equations 3 and 4 (defining b = b 1 + b 2 ) (Blanpied et al, 1998; Reinen & Weeks, 1993), which for our data provides a better fit to the data than using one state variable.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Commonly, experimental friction data are superimposed by a small background trend of slip hardening or slip weakening (e.g., Blanpied et al, 1998; Ikari et al, 2013). When modeling our experimental data, we remove these long‐term slip‐dependent friction trends (e.g., Skarbek & Savage, 2019) as needed in order to avoid biasing and to separate the friction velocity dependence from effects of friction slip dependence (Ikari et al, 2013; Ito & Ikari, 2015).…”

Section: Experimental Methodsmentioning

confidence: 99%

Frictional Strengthening Explored During Non‐Steady State Shearing: Implications for Fault Stability and Slip Event Recurrence Time

et al. 2020

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On natural faults that host repeating slip events, the inter-event loading time is quite large compared to the slip event duration. Since most friction studies focus on steady-state frictional behavior, the fault loading phase is not typically examined. Here, we employ a method specifically designed to evaluate fault strength evolution during active loading, under shear driving rates as low as 10 −10 m/s, on natural fault gouge samples from the Waikukupa Thrust in southern New Zealand. These tests reveal that in the early stages of loading following a slip event, there is a period of increased stability, which fades with accumulated slip. In the framework of rate-and state-dependent friction laws, this temporary stable phase exists as long as slip is less than the critical slip distance and the elapsed time is less than the value of the state variable at steady state. These observations indicate a minimum earthquake recurrence time, which depends on the field value of the critical slip distance and the background slip rate. We compare estimates of minimum earthquake recurrence times with the recurrence times of repeating large earthquakes on the Alpine Fault in southern New Zealand and repeating small-magnitude earthquakes on the San Andreas Fault system in California. We find that the observed recurrence times are mostly longer than the predicted minimum values, and exceptions in the San Andreas system may be explained by elevated slip rates due to larger earthquakes in this region.

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RSFit3000: A MATLAB GUI-Based Program for Determining Rate and State Frictional Parameters from Experimental Data

Cited by 18 publications

References 25 publications

Fault Reactivation During Fluid Pressure Oscillations: Transition From Stable to Unstable Slip

Fault Reactivation During Fluid Pressure Oscillations: Transition From Stable to Unstable Slip

Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes

Frictional Strengthening Explored During Non‐Steady State Shearing: Implications for Fault Stability and Slip Event Recurrence Time

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