Numerical modelling of complex rheologies

Coord.: B. Kaus (JGU) & P. Tackley (ETH) 

This WP reunites 5 numerical modelling projects. Three of these projects analyze the role of history-dependent rheologies on plate tectonics and mantle convection. The fourth project works on a shorter time and smaller spatial scale, focusing on the interactions between fluids and deformation in geothermal reservoirs.

ESR9. Plate tectonics: strain localization due to anisotropy in the lithospheric mantle . Supervisors: A Tommasi (Geosciences Montpellier). Secondments: ETH & APERAM
Objectives: Investigate the role of an anisotropy of physical properties due to preferred orientation of olivine crystals in the lithospheric mantle on global plate tectonics using a 3-D multiscale approach combining finite-element models of lithosphere-scale deformation with viscoplastic self-consistent simulations of evolving anisotropic physical properties. For this, we will develop new modelling routines for simulating the evolution of mechanical anisotropy function of the deformation history. These models will be used for studying the reactivation of lithospheric structures on the formation of new plate boundaries.
Expected Results: A better understanding of the processes allowing for strain localization in the ductile regime; a parameterized description of deformation-induced mechanical anisotropy that can be incorporated into 3-D convection codes.

ESR12. Modelling crack propagation and fluid injection (hydrofracturing) applied to geothermics Supervisors: B. Kaus (JGU) & H. Deckert (IGEM). Secondments: Univ. Bristol & GMuG
Objectives: (1) Develop new software to model hydrofracturing in heterogeneous viscoelastoplastic rocks in 3D using massively parallel high-performance computers; (2) Perform systematic simulations to understand how stress states and heterogeneities affect crack propagation, (3) Compare the simulations with natural data and (4) with laboratory experiments
Expected Results: A new massively-parallel 3D code capable of simulating hydrofracturing in poro-viscoelastoplastic rocks and allowing to quantify how hydrofracturing influences the local state of stress and the effective rheology of the reservoir

ESR15. Large-scale mantle dynamics: Influence of evolving microstructures. Supervisors: P. Tackley, T. Gerya (ETH). Secondments: Univ. Mainz (JGU) & Rockfield
Objectives: Investigate numerically how evolving grain texture, including grain size and alignment (anisotropy) influences three different aspects of plate tectonics and mantle dynamics: (i) how reactivation of previous plate boundaries, in particular continental rifting, is influenced by history-dependent rheology arising from microstructural properties (ii) how lithospheric weakening may be caused by grain evolution including pinning by minor phases, (iii) the influence of grain-size evolution and anisotropy on large-scale mantle dynamics, including weakness of subducting slabs caused by grain-size reduction at phase transitions, and deep mantle anisotropy
Expected Results: New models allowing to study the feedbacks between microstructural evolution and rheology, A greater understanding of the role of microstructural evolution on the arisal of plate tectonics.

ESR16 . Rheological controls of seismicity along lithospheric plate boundaries. Supervisors: P. Tackley, T. Gerya, Y. van Dinther  (ETH). Secondments: Uniroma TRE & Schlumberger
Objectives: Investigate the rheological controls of spatio-temporal variability of seismicity along convergent, divergent and transform plate boundaries using a seismo-thermo-mechanical (STM) geodynamic modelling approach, comprising 3 steps: (i) modelling long-term seismicity patterns for three different lithospheric boundary types and understand differences between them, (ii) modelling transient seismicity associated with emerging plate boundaries (iii) studying how history-dependent rheology arising from brittle fracturing, microstructural changes, hydration/dehydration reactions and fluid/melt percolation affects the spatiotemporal variability of seismicity.
Expected Results: Gain insight into the evolution of seismicity distribution and earthquake cycles at plate boundaries.

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