Steady shear and thermal run-away in clayey gouges

In the present paper we study the thermo-viscoplastic coupling in clayey fault-gouges under shear. It is shown that steady shear for a strain-rate hardening/thermally softening clay is only then possible, if the ambient temperature is less than some well-defined critical value. Past this critical temperature the balance between the two antagonistic mechanisms of viscous strengthening and thermal softening cannot be sustained and may result in dynamic (catastrophic) shear deformation