Le Geotop - Dr Frédéric Gueydan et Maxime Bernaudin : Rheology of the continental... (26-01-2018)

Dr Frédéric Gueydan et Maxime Bernaudin : Rheology of the continental... (26-01-2018)

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Dr. Frédéric Gueydan
Dr. Maxime Bernaudin
(Géosciences Montpellier, U. de Montpellier)

Rheology of the continental lithosphere. Implications for transient events (SSE/ETS) and intraplate seismicity

Vendredi 26 janvier 2018 à 11h15/ Friday, January 26, 2018, 11:15 am

Local PK-7605, 201 ave. Président-Kennedy, UQAM

Résumé / Abstract:

No single rheological model is up-to-now comprehensive enough to simultaneously describe weak behaviour of plate boundaries and rigid-like behaviour of plate interiors. The extrapolation of laboratory flow laws to geological scale suggests a complex layering of brittle and ductile layers in which the upper mantle is brittle and support high stresses. Such a rheological layering is moreover important to reproduce first-order patterns of lithosphere deformation. By contrast, recent geophysical studies suggest a high-strength lower crust and a weak ductile upper mantle.

Geological constraints on lithospheric strength and large strain numerical experiments reveal that the development of layers containing weak minerals and the onset of grain boundary sliding upon grain size reduction in olivine cause strain localisation and reduce strength in the crust and subcontinental mantle, respectively. The positive feedback between weakening and strain localization leads to the progressive development of weak plate boundaries while plate interiors remain strong.

On these bases, we will discuss possible implications for intraplate seismicity and the generation of transient phenomena (such as SSE and ETS) at plate interface.