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| Titel |
Thermo-mechanical model for the finite strain gradient in kilometer-scale shear zones |
| VerfasserIn |
Arthur Bauville, Stefan Schmalholz |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075838
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| Zusammenfassung |
| Many kilometer-scale crustal shear zones with thrust shear sense exhibit a similar nonlinear
decrease of the finite shear strain (γ) with increasing distance (z) from the shear zone’s base.
To explain this strain gradient, we use a one-dimensional (1-D) thermo-mechanical
shear zone model which considers a dislocation creep flow law with temperature
dependent viscosity. The model predicts a linear finite strain gradient in ln(γ) - z space,
which is quantified by the single dimensionless parameter β. β depends on the
activation energy (Q), the temperature at the shear zone’s base (T0) and the temperature
difference across it (ΔT), which are often well constrained parameters. We apply our
model to several shear zones worldwide. Our model is based on physics and fits
the strain data as well as previously published empirical functions. The estimates
of β resulting from fitting the finite strain gradient agree with other independent
estimates of β using realistic values for Q, T0 and ΔT reported for the considered
shear zones. This agreement of independent β estimates indicates that the model is
physically feasible and that the dominant cause for the nonlinear strain gradient in
kilometer-scale shear zones can be the temperature increase toward the shear zone’s base
and the related decrease in viscosity. he model, however, often underestimates the
strain gradient in the lowermost part of natural shear zones. This underestimation
indicates that additional processes such as grain-size reduction or viscous heating, not
considered in the model, play an important role close to the base of the shear zone. |
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