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Ylona Van Dinther - One of the best experts on this subject based on the ideXlab platform.
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An Invariant Rate‐ and State‐Dependent Friction Formulation for Viscoeastoplastic Earthquake Cycle Simulations
Journal of Geophysical Research: Solid Earth, 2018Co-Authors: Robert Herrendörfer, Taras Gerya, Ylona Van DintherAbstract:We present a 2-D numerical modeling approach for simulating a wide slip spectrum in a viscoelastoplastic continuum. The key new model component is an invariant reformulation of the classical rate- and state-Dependent Friction equations, which is designed for earthquake simulations along spontaneously evolving faults. Here we describe the methodology and demonstrate that it is accurate and stable in a setup consisting of a mature strike-slip fault zone. We show that the nucleation and propagation of an earthquake are well resolved, as supported by a good agreement with various analytical approximations, including those of the nucleation and cohesive zone lengths. Results generally converge with respect to grid size, time step, and other numerical parameters. The convergence rate with respect to grid size depends on the internodal averaging scheme, is influenced by wave reflections, and deteriorates for inclined faults. The simulated slip spectrum, ranging from stable sliding at the loading rate to periodic aseismic slip to periodic seismic slip as a function of nucleation size, is in general agreement with the literature. In this simple setup, dynamic pressure does not play a significant role. By analyzing the role of viscous deformation, we identify and confirm by our simulations a theoretical viscosity threshold below which earthquakes cannot nucleate. This threshold is shown to depend on the reference strength of rate- and state-Dependent Friction and the loading strain rate, which is in agreement with previous work on the brittle-ductile transition.
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an invariant rate and state Dependent Friction formulation for viscoeastoplastic earthquake cycle simulations
Journal of Geophysical Research, 2018Co-Authors: Robert Herrendörfer, Taras Gerya, Ylona Van DintherAbstract:We present a 2-D numerical modeling approach for simulating a wide slip spectrum in a viscoelastoplastic continuum. The key new model component is an invariant reformulation of the classical rate- and state-Dependent Friction equations, which is designed for earthquake simulations along spontaneously evolving faults. Here we describe the methodology and demonstrate that it is accurate and stable in a setup consisting of a mature strike-slip fault zone. We show that the nucleation and propagation of an earthquake are well resolved, as supported by a good agreement with various analytical approximations, including those of the nucleation and cohesive zone lengths. Results generally converge with respect to grid size, time step, and other numerical parameters. The convergence rate with respect to grid size depends on the internodal averaging scheme, is influenced by wave reflections, and deteriorates for inclined faults. The simulated slip spectrum, ranging from stable sliding at the loading rate to periodic aseismic slip to periodic seismic slip as a function of nucleation size, is in general agreement with the literature. In this simple setup, dynamic pressure does not play a significant role. By analyzing the role of viscous deformation, we identify and confirm by our simulations a theoretical viscosity threshold below which earthquakes cannot nucleate. This threshold is shown to depend on the reference strength of rate- and state-Dependent Friction and the loading strain rate, which is in agreement with previous work on the brittle-ductile transition.
Jean Philippe Avouac - One of the best experts on this subject based on the ideXlab platform.
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Slip-rate-Dependent Friction as a universal mechanism for slow slip events
Nature Geoscience, 2020Co-Authors: Demian M Saffer, Chris Marone, Jean Philippe AvouacAbstract:A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events (SSEs) and their wide range of depths, slip rates, durations, stress drops and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening Frictional sliding at low slip rates towards rate-neutral or rate-strengthening behaviour at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-Dependent transition quantitatively explains the experimental data for natural fault rocks representative of materials in the source regions of SSEs. With a standard constant-parameter rate-and-state Friction law, SSEs arise only near the threshold for slip instability. The inclusion of velocity-Dependent Friction parameters substantially broadens the range of conditions for slow slip occurrence, and produces a wide range of event characteristics, which include stress drop, duration and recurrence, as observed in nature. Upscaled numerical simulations that incorporate parameters consistent with laboratory measurements can reproduce geodetic observations of repeating SSEs on tectonic faults. We conclude that slip-rate-Dependent Friction explains the ubiquitous occurrence of SSEs in a broad range of geological environments. A transition from rate-weakening to rate-strengthening Frictional behaviour with increasing slip rate could explain the observed diversity of slow slip events on faults, according to numerical simulations.
Chris Marone - One of the best experts on this subject based on the ideXlab platform.
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Slip-rate-Dependent Friction as a universal mechanism for slow slip events
Nature Geoscience, 2020Co-Authors: Demian M Saffer, Chris Marone, Jean Philippe AvouacAbstract:A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events (SSEs) and their wide range of depths, slip rates, durations, stress drops and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening Frictional sliding at low slip rates towards rate-neutral or rate-strengthening behaviour at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-Dependent transition quantitatively explains the experimental data for natural fault rocks representative of materials in the source regions of SSEs. With a standard constant-parameter rate-and-state Friction law, SSEs arise only near the threshold for slip instability. The inclusion of velocity-Dependent Friction parameters substantially broadens the range of conditions for slow slip occurrence, and produces a wide range of event characteristics, which include stress drop, duration and recurrence, as observed in nature. Upscaled numerical simulations that incorporate parameters consistent with laboratory measurements can reproduce geodetic observations of repeating SSEs on tectonic faults. We conclude that slip-rate-Dependent Friction explains the ubiquitous occurrence of SSEs in a broad range of geological environments. A transition from rate-weakening to rate-strengthening Frictional behaviour with increasing slip rate could explain the observed diversity of slow slip events on faults, according to numerical simulations.
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a microphysical interpretation of rate and state Dependent Friction for fault gouge
Geochemistry Geophysics Geosystems, 2016Co-Authors: Brett M Carpenter, Matt J Ikari, Chris MaroneAbstract:The evolution of fault strength during the seismic cycle plays a key role in the mode of fault slip, nature of earthquake stress drop, and earthquake nucleation. Laboratory-based rate- and state-Dependent Friction (RSF) laws can describe changes in fault strength during slip, but the connections between fault strength and the mechanisms that dictate the mode of failure, from aseismic creep to earthquake rupture, remain poorly understood. The empirical nature of RSF laws remains a drawback to their application in nature. Here we analyze an extensive data set of Friction constitutive parameters with the goal of illuminating the microphysical processes controlling RSF. We document robust relationships between: (1) the initial value of sliding (or kinetic) Friction, (2) RSF parameters, and (3) the time rates of Frictional strengthening (aging). We derive a microphysical model based on asperity contact mechanics and show that these relationships are dictated by: (1) an activation energy that controls the rate of asperity growth by plastic creep, and (2) an inverse relationship between material hardness and the activation volume of plastic deformation. Collectively, our results illuminate the physics expressed by the RSF parameters, and which describe the absolute value of Frictional strength and its dependence on time and slip rate. Moreover, we demonstrate that seismogenic fault behavior may be dictated by the interplay between grain properties and ambient conditions controlling the local shear strength of grain-scale asperity contacts.
Eli Pollak - One of the best experts on this subject based on the ideXlab platform.
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A theory for the activated barrier crossing rate constant in systems influenced by space and time Dependent Friction
The Journal of Chemical Physics, 1994Co-Authors: George R. Haynes, Gregory A. Voth, Eli PollakAbstract:A general theory is presented for the thermally activated rate constant in systems influenced by spatially Dependent and time correlated Friction. The theory is valid at all damping strengths and goes uniformly from the energy diffusion limit to the spatial diffusion limit. Results of the theory for a model system with an exponentially time correlated and spatially Dependent Friction kernel are compared with results from a numerically exact solution of the equivalent generalized Langevin equation. Predictions of the theory are found to be in excellent agreement with the numerical simulation results. The phenomenon of memory suppression of the rate is observed for long time scale Frictions and its modification due to the spatial dependence of the Friction is discussed. The effects of spatially Dependent Friction can be understood through a quantity called the ‘‘average spatial modification’’ of the coupling between the reaction coordinate and the environment.
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Fokker–Planck equation for nonlinear stochastic dynamics in the presence of space and time Dependent Friction
The Journal of Chemical Physics, 1993Co-Authors: Eli Pollak, Alexander M. BerezhkovskiiAbstract:The one‐dimensional stochastic equation of motion for a particle in the presence of space and time Dependent Friction involves multiplicative fluctuations and a nonlinear Friction kernel. We show how this rather complicated equation may be significantly simplified. Introduction of an auxiliary mode leads to a set of two nonlinearly coupled equations with space and time inDependent damping. An exact Fokker–Planck equation emerges naturally from this formulation.
Robert Herrendörfer - One of the best experts on this subject based on the ideXlab platform.
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An Invariant Rate‐ and State‐Dependent Friction Formulation for Viscoeastoplastic Earthquake Cycle Simulations
Journal of Geophysical Research: Solid Earth, 2018Co-Authors: Robert Herrendörfer, Taras Gerya, Ylona Van DintherAbstract:We present a 2-D numerical modeling approach for simulating a wide slip spectrum in a viscoelastoplastic continuum. The key new model component is an invariant reformulation of the classical rate- and state-Dependent Friction equations, which is designed for earthquake simulations along spontaneously evolving faults. Here we describe the methodology and demonstrate that it is accurate and stable in a setup consisting of a mature strike-slip fault zone. We show that the nucleation and propagation of an earthquake are well resolved, as supported by a good agreement with various analytical approximations, including those of the nucleation and cohesive zone lengths. Results generally converge with respect to grid size, time step, and other numerical parameters. The convergence rate with respect to grid size depends on the internodal averaging scheme, is influenced by wave reflections, and deteriorates for inclined faults. The simulated slip spectrum, ranging from stable sliding at the loading rate to periodic aseismic slip to periodic seismic slip as a function of nucleation size, is in general agreement with the literature. In this simple setup, dynamic pressure does not play a significant role. By analyzing the role of viscous deformation, we identify and confirm by our simulations a theoretical viscosity threshold below which earthquakes cannot nucleate. This threshold is shown to depend on the reference strength of rate- and state-Dependent Friction and the loading strain rate, which is in agreement with previous work on the brittle-ductile transition.
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an invariant rate and state Dependent Friction formulation for viscoeastoplastic earthquake cycle simulations
Journal of Geophysical Research, 2018Co-Authors: Robert Herrendörfer, Taras Gerya, Ylona Van DintherAbstract:We present a 2-D numerical modeling approach for simulating a wide slip spectrum in a viscoelastoplastic continuum. The key new model component is an invariant reformulation of the classical rate- and state-Dependent Friction equations, which is designed for earthquake simulations along spontaneously evolving faults. Here we describe the methodology and demonstrate that it is accurate and stable in a setup consisting of a mature strike-slip fault zone. We show that the nucleation and propagation of an earthquake are well resolved, as supported by a good agreement with various analytical approximations, including those of the nucleation and cohesive zone lengths. Results generally converge with respect to grid size, time step, and other numerical parameters. The convergence rate with respect to grid size depends on the internodal averaging scheme, is influenced by wave reflections, and deteriorates for inclined faults. The simulated slip spectrum, ranging from stable sliding at the loading rate to periodic aseismic slip to periodic seismic slip as a function of nucleation size, is in general agreement with the literature. In this simple setup, dynamic pressure does not play a significant role. By analyzing the role of viscous deformation, we identify and confirm by our simulations a theoretical viscosity threshold below which earthquakes cannot nucleate. This threshold is shown to depend on the reference strength of rate- and state-Dependent Friction and the loading strain rate, which is in agreement with previous work on the brittle-ductile transition.