Séminaire IUSTI – 7 janvier 2022 – 11h salle 250

Rheologies for the Earth’s brittle crust

Jean-Arthur Olive – ENS, Paris

Most of the brittle, earthquake-generating deformation that shapes mountain ranges takes place in the uppermost ~15 km of the Earth’s crust. On short time scales, the upper crust deforms by slip on frictional faults that delineate elastic blocks. Over millions of years, however, large non-recoverable deformation accumulates both on and off-faults, and distributed brittle strain can localize to form new fault systems. This complex rheological behavior is typically modeled as Mohr-Coulomb elasto-plasticity, with a range of ad-hoc softening parameters that lack a clear micro-mechanical interpretation. I will discuss possible adjustements to this framework aimed at (1) better capturing key properties of crustal rocks inferred from laboratory experiments, and (2) better representing the mineral-scale processes which underlie brittle failure. Improved constitutive laws for the brittle upper crust are a necessary step towards a unified description of geological processes, from mineral to crustal scale, and from seconds to millions of years.