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| Titel |
Microphysically derived expressions for rate-and-state friction and fault
stability parameters |
| VerfasserIn |
Jianye Chen, André Niemeijer, Christopher Spiers |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143899
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| Publikation (Nr.) |
 EGU/EGU2017-7665.pdf |
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| Zusammenfassung |
| Rate-and-state friction (RSF) laws and associated parameters are extensively applied to fault
mechanics, mainly on an empirical basis with a limited understanding of the underlying
physical mechanisms. We recently established a general microphysical model [Chen and
Spiers, 2016], for describing both steady-state and transient frictional behavior of any
granular fault gouge material undergoing deformation by granular flow plus an arbitrary
creep mechanism at grain contacts, such as pressure solution. We further showed that the
model is able to reproduce typical experimental frictional results, namely “velocity stepping”
and “slide-hold-slide” sequences, in satisfactory agreement with the main features and trends
observed.
Here, we extend our model, which we explored only numerically thus far, to obtain
analytical solutions for the classical rate and state friction parameters from a purely
microphysical modelling basis. By analytically solving the constitutive equations of the
model under various boundary conditions, physically meaningful, theoretical expressions for
the RSF parameters, i.e. a, b and Dc, are obtained. We also apply linear stability analysis to a
spring-slider system, describing interface friction using our model, to yield analytical
expressions of the critical stiffness (Kc) and critical recurrence wavelength (Wc) of the
system. The values of a , b and Dc, as well as Kc and Wc, predicted by these expressions
agree well with the numerical modeling results and acceptably with values obtained
from experiments, on calcite for instance. Inserting the parameters obtained into
classical RSF laws (slowness and slip laws) and conducting forward modelling gives
simulated friction behavior that is fully consistent with the direct predictions of our
numerically implemented model. Numerical tests with friction obeying our model show
that the slip stability of fault motion exhibits a transition from stable sliding, via
self-sustained oscillations, to stick slips with decreasing elastic stiffness, decreasing loading
rate, and increasing normal stress, which is fully consistent with our linear stability
analysis and also with previous RSF models that employed constant values of the RSF
parameters.
Importantly, our analytical expressions for. a, b, Dc, Kc and Wc, are functions of the
internal microstructure of the fault (porosity, grain size and shear zone thickness), the
material properties of the fault gouge (e.g. creep law parameters like activation energy,
stress sensitivity, grain size sensitivity), and the ambient conditions the fault is
subjected to (temperature and normal stress). The expressions obtained thus have clear
physical meaning allowing a more meaningful extrapolation to natural conditions. On
the basis of these physics-based expressions, seismological implications for slip
on natural faults (e.g. subduction zone interfaces, faults in carbonate terrains) are
discussed.
Reference
Chen, J., and C. J. Spiers (2016), Rate and state frictional and healing behavior of
carbonate fault gouge explained using microphysical model, J. Geophys. Res., 121,
doi:10.1002/2016JB013470. |
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