SUPPLEMENTARY INFORMATION

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1 SUPPLEMENTARY INFORMATION Supplementary material to "Crystal-scale control on plate tectonics: anisotropy-induced reactivation of lithospheric faults" Andréa Tommasi *, Mickael Knoll *,***, Alain Vauchez *, Javier W. Signorelli **, Catherine Thoraval *, Roland Logé *** * Geosciences Montpellier, CNRS & Université de Montpellier 2, Pl. E Bataillon, Montpellier cedex 5, France. ** Instituto de Fisica de Rosario, CONICET, Universidad Nacional de Rosario, 2000 Rosario, Argentina. *** MINES ParisTech, CEMEF Center for Materials Forming, BP207, Sophia Antipolis Cedex, France. Supplementary Discussion: Texture-induced viscoplastic anisotropy of olivine-rich rocks - comparison between model predictions and experimental data: High-pressure and high-temperature torsion experiments on olivine aggregates in the dislocation creep regime show about 15 to 20% strain weakening before steady-state behaviour 1. The evolution is not linear; the strongest decrease in deviatoric stresses (~15%) is observed between shear strains of 0.1 and 0.5. This strain weakening may be related to the evolution of olivine texture (crystal preferred orientation), which is fast for shear strains 1 and slows down after, probably due to the onset of dynamic recrystallization. Considering a stress exponent of 3, a contrast in deviatoric stress by a factor 1.2 will correspond to a factor 1.7 in strain rates. This factor is slightly higher than the strain rate ratios observed in the present models, in which the initial texture in the 'inherited shear zone' is weak (Fig. 1). It is nevertheless reproduced if stronger textures, similar to those produced in the experiments and observed in naturally deformed peridotites, are used in the 'inherited shear zone' (Fig. S4). 1 Bystricky, M., Kunze, K., Burlini, L., & Burg, J.P., High shear strain of olivine aggregates; rheological and seismic consequences. Science 290 (5496), (2000). nature geoscience 1

2 supplementary information Supplementary Figures: Supplementary Figure S1: Scheme of the multi-scale anisotropic models. 2 nature geoscience

3 supplementary information Supplementary Figure S2: Geometry, boundary conditions, and Von Mises equivalent strain rate ε eq distribution in a model with an inherited transcurrent shear zone or transpressional belt normal to the imposed extension direction after a total stretching of 20%. Texture-induced anisotropy results in lower strain rates in the 'inherited zone' relatively to the surroundings. Upper left insert displays the initial olivine texture within the 'inherited zone'. nature geoscience 3

4 supplementary information Supplementary Figure S3: Results for a model with geometry and boundary conditions as in Fig. 1, but with an initial texture twice as strong (J index =6). (a, b) Poloidal and toroidal partitioning, represented as maps of the divergence and vorticity of the horizontal flow field, respectively. Higher divergence marks localization of the poloidal flow in the inherited texture domain. Toroidal flow is restricted to the inherited texture domain. Flow in the surroundings is purely poloidal, in agreement with the boundary conditions (extension parallel to the X direction). Note that the divergence and vorticity variation ranges are respectively 2 and 3 times larger than those in the 45 model with a weaker initial texture (J index =3, Fig. 3), highlighting that changes in the texture intensity affect more the toroidal-poloidal partitioning than the strain localization. (c) Evolution of the strain rate (normalized by the initial Von Mises equivalent strain rate ε eq = 2 3 ε ij ε ij in the surrounding medium) as a function of the total finite stretching. In agreement with the change in divergence and vorticity ranges relatively to the reference model (J index =3), the more concentrated texture results in a marked increase in horizontal shearing parallel to the pre-existing structure trend, but in limited enhancement of the normal strain rates (horizontal stretching and vertical thinning). 4 nature geoscience

5 supplementary information Supplementary Figure S4: (a) Geometry, boundary conditions, and Von Mises equivalent strain rate ε eq distribution in a model in which strike-slip motion is imposed parallel to an 'inherited strike-slip shear zone' after a total shear strain of Texture-induced anisotropy results in progressive strain localization in the inherited shear zone. Upper left insert displays the initial olivine texture in the inherited shear zone. (b) Evolution of the strain rate (normalized by the initial Von Mises equivalent strain rate ε eq = 2 3 ε ij ε ij in the surrounding medium) as a function of the total shear strain in the 'inherited shear zone' (thick lines) and in the surrounding medium (thin lines). Texture evolution in both domains results in increasing strain localization in the inherited shear zone. Asymmetry of the olivine texture relative to the shear zone trend triggers extension normal to it and vertical thinning. nature geoscience 5