Gardner, R, Piazolo, S orcid.org/0000-0001-7723-8170, Evans, L et al. (1 more author) (2017) Patterns of strain localization in heterogeneous, polycrystalline rocks – a numerical perspective. Earth and Planetary Science Letters, 463. pp. 253-265. ISSN 0012-821X
Abstract
The spatial and temporal patterns of strain localization in materials with pre-existing heterogeneities are investigated via a series of two-dimensional numerical models. Models include (i) a dynamic feedback process, to simulate rheological weakening in response to the transition from non-linear flow (dislocation creep) to linear flow (diffusion creep/grain boundary sliding), and (ii) a time dependent strengthening process, counteracting the weakening process. Different load bearing framework geometries with 20% weak component are used to evaluate the impact of geometry on the strength of the material and its ability to localize strain into an interconnected weak layer (IWL). Our results highlight that during simple shear, if dynamic weakening with or without strengthening feedbacks is present, strain is quickly localized into an IWL, where an increasing proportion of weak material increases the interconnections between the IWLs, thereby increasing the anastomosing character of the shear zones. We establish that not only bulk strain localization patterns but also their temporal patterns are sensitive to the dominance of the weakening or strengthening process. Consequently, shear zones are dynamic in time and space within a single deformation event. Hence, the pattern of finite strain can be an incomplete representation of the evolution of a shear zone network.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Editors: |
|
Copyright, Publisher and Additional Information: | © 2017 Elsevier B.V. This is an author produced version of a paper published in Earth and Planetary Science Letters. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | anastomosing; shear zone; dynamic weakening; material strength; geometry; weak component |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 06 Mar 2017 11:22 |
Last Modified: | 09 Mar 2018 05:24 |
Published Version: | https://doi.org/10.1016/j.epsl.2017.01.039 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.epsl.2017.01.039 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:113261 |
Downloads
Filename: Gardner et al _SuppData.pdf
Description: Supplementary data includes a flow diagram of the numerical model, information on the material strength bound calculation, incremental and accumulated strain plots for simulation set I and information on the supplied movies of the numerical model.
Filename: SuppMovie1.avi
Description: Simulation set III: Vertical stripe geometry with σThr = 6.0 showing the development of an interconnected weak layer (IWL). Movie is of stress in the polygons. Brown areas are relatively higher stress. At ∼10 s, the IWL is initiated with higher stress are
Filename: SuppMovie2.avi
Description: Simulation set III: Vertical stripe geometry with σThr = 6.0. This is from the same run as for movie 1, but shows the incremental strain in the polygons.
Filename: SuppMovie3.avi
Description: Simulation set IV: Cluster geometry with σThr = 5.0 and AThr = 15 showing development of anatomosing IWLs. Movie is of incremental strain in the 100 × 100 square grid of unconnected nodes. The strain in the IWLs varies over time due to the logic in Fig. 1
Filename: SuppMovie3a.avi
Description: Shows movie 3 continued to γ of ∼2.75. It shows by γ of ∼2.5 the IWL is dormant, and no longer concentrating any strain.
Filename: SuppMovie4.avi
Description: Simulation set IV: Incremental strain in cluster geometry with σThr = 4.0 and AThr = 15 for comparison with movie 3 to show impact of increased weakening (i.e. reduced stress threshold) – strain is more distributed.
Filename: SuppMovie5.avi
Description: Simulation set IV: Incremental strain in cluster geometry with σThr = 6.0 and AThr = 15 for comparison with movie 3 to show impact of decreased weakening (i.e. increased stress threshold) – strain is more concentrated.
Filename: SuppMovie6.avi
Description: Simulation set IV: Incremental strain in cluster geometry with σThr = 5.0 and AThr = 5 for comparison with movie 3 to show impact of increased strengthening (i.e. decreased age threshold) – increased strain variability in the IWLs.
Filename: SuppMovie7.avi
Description: Simulation set IV: Incremental strain in cluster geometry with σThr = 5.0 and AThr = 10 for the 100 × 100 square grid of unconnected nodes (movie 3), showing only those nodes where εIncr > 0.06 – strain in the IWLs varies over time.