## Initiation of localized shear zones in viscoelastoplastic rocks

### Détails

ID Serval

serval:BIB_46598E1A8FD7

Type

**Article**: article d'un périodique ou d'un magazine.

Collection

Publications

Fonds

Titre

Initiation of localized shear zones in viscoelastoplastic rocks

Périodique

Journal of Geophysical Research - Solid Earth

ISSN-L

0148-0227

Statut éditorial

Publié

Date de publication

2006

Peer-reviewed

Oui

Volume

111

Pages

B04412

Langue

anglais

Résumé

[1] Shear localization is a process of primary importance for the

onset of subduction and the evolution of plate tectonics on Earth. In

this paper we focus on a model in which shear localization is initiated

through shear heating. The rheology employed is linear Maxwell

viscoelastic with von Mises plasticity and an exponential dependence of

viscosity on temperature. Dimensional analysis reveals that four

nondimensional (0-D) parameters control the initiation of shear zones.

The onset of shear localization is systematically studied with 0-D, 1-D,

and 2-D numerical models, both under constant stress and under constant

velocity boundary conditions. Mechanical phase diagrams demonstrate that

six deformation modes exist under constant velocity boundary conditions.

A constant stress boundary condition, on the other hand, exhibits only

two deformation modes ( localization or no localization). Scaling laws

for the growth rate of temperature are computed for all deformation

modes. Numerical and analytical solutions demonstrate that diffusion of

heat may inhibit localization. Initial heterogeneities are required to

initiate localization. The derived scaling laws are applied to

Earth-like parameters. For a given heterogeneity size, stable

(nonseismic) localization only occurs for a certain range of effective

viscosities. Localization is inhibited if viscosity is smaller then a

minimum threshold, which is a function of the heterogeneity size. The

simplified rheological model is compared with a more realistic and more

complex model of olivine that takes diffusion, power law, and Peierls

creep into account. Good agreement exists between the models. The

simplified model proposed in this study thus reproduces the main physics

of ductile faulting. Two-dimensional late stage simulations of

lithospheric-scale shear localization are presented that confirm the

findings of the initial stage analysis.

onset of subduction and the evolution of plate tectonics on Earth. In

this paper we focus on a model in which shear localization is initiated

through shear heating. The rheology employed is linear Maxwell

viscoelastic with von Mises plasticity and an exponential dependence of

viscosity on temperature. Dimensional analysis reveals that four

nondimensional (0-D) parameters control the initiation of shear zones.

The onset of shear localization is systematically studied with 0-D, 1-D,

and 2-D numerical models, both under constant stress and under constant

velocity boundary conditions. Mechanical phase diagrams demonstrate that

six deformation modes exist under constant velocity boundary conditions.

A constant stress boundary condition, on the other hand, exhibits only

two deformation modes ( localization or no localization). Scaling laws

for the growth rate of temperature are computed for all deformation

modes. Numerical and analytical solutions demonstrate that diffusion of

heat may inhibit localization. Initial heterogeneities are required to

initiate localization. The derived scaling laws are applied to

Earth-like parameters. For a given heterogeneity size, stable

(nonseismic) localization only occurs for a certain range of effective

viscosities. Localization is inhibited if viscosity is smaller then a

minimum threshold, which is a function of the heterogeneity size. The

simplified rheological model is compared with a more realistic and more

complex model of olivine that takes diffusion, power law, and Peierls

creep into account. Good agreement exists between the models. The

simplified model proposed in this study thus reproduces the main physics

of ductile faulting. Two-dimensional late stage simulations of

lithospheric-scale shear localization are presented that confirm the

findings of the initial stage analysis.

Création de la notice

09/10/2012 20:50

Dernière modification de la notice

18/11/2016 14:20