Shear localization in foliated media: numerical experiments with application to the Bethique (Spain).

Field data have been gathered in the Bethique (Spain) and studied systematically at map, outcrop and thin section scale. The field area has been chosen for being lithologically homogeneous at map scale and the results indicates a systematic angle of 22° between the shear bands and the schistosity. Trying to understand the systematics in this observation, we have design a numerical parametric study that consists of hundreds of numerical runs in which we consider a initial 4 by 1 rectangular section filled by layers of two visco-elasto-plastic material of different viscosity. We neglect the effect of temperature and gravity. Instead of modeling the whole crust, we account for a confining pressure. The sections were sheared up to γ = 1.5 in bulk.