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Multiphysics Modeling of a Brittle‐Ductile Lithosphere: 1. Explicit Visco‐Elasto‐Plastic Formulation and Its Numerical Implementation
Author(s) -
Jacquey Antoine B.,
Cacace Mauro
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb018474
Subject(s) - lithosphere , geology , brittleness , rheology , multiphysics , geophysics , geodynamics , viscoelasticity , mechanics , deformation (meteorology) , geomechanics , geotechnical engineering , finite element method , tectonics , seismology , materials science , structural engineering , physics , engineering , oceanography , composite material
The long‐term strength of the lithosphere is controled by two different modes of deformation: a brittle‐like, effective pressure‐sensitive behavior at shallow crustal depth, which gradually transits to a thermally activated ductile flow rheology with increasing depth. All applications dealing with long‐term tectonics therefore share the necessity to describe in a consistent way the multiphysics coupling among the different deformation mechanisms controlling the bulk behavior of the lithosphere. We describe an efficient numerical implementation of a consistent visco‐elasto‐plastic rheology suitable to describe the first‐order aspects of continental rock masses. Different from typical long‐term geodynamics numerical frameworks, we explicitly account for both volumetric and deviatoric response of lithospheric rocks to applied loads. Plastic correction to a viscoelastic stress state is introduced via a non‐associative Drucker‐Prager model, without resorting to the assumption of a plastic limiter. The transient behavior of crustal and lithospheric rocks is accounted for by an overstress (rate‐dependent) viscoplastic rheology, which additionally helps solving for numerical issues related to plastic strain accumulation even in the absence of energetic feedbacks. When applied to the study of the dynamics of plume‐lithosphere interactions, our implementation is able to reproduce a surface topography with complex multiharmonic wavelength patterns in agreement with observations. In the final chapter, we discuss main limitations of the current rheological description when applied to the study of transient semi‐brittle rock behavior. These aspects are tackled in a companion paper, where a thermodynamically consistent formulation extending the current numerical description is presented.