NEW APPARATUS FOR THERMOMECHANICAL ANALOGUE MODELING

Abstract

A new apparatus designed for thermomechanical analogue modeling to investigate tectonic crustal-scale processes, in particular the role of rheology in the distribution and propagation of deformation, is presented. By inducing a vertical thermal gradient through suitable analogue materials and controlling heat flow into the bottom and out of the top of the model, a precise viscosity gradient can be obtained. For the temperature range employed, paraffin wax shows a viscosity range of more than 11 orders of magnitude. A maximum of ~60% shortening or 200% extension is possible in the horizontal direction. The machine can determine the applied force, the horizontal shortening, and the model height at two locations. The bulk rheology is estimated from the calculated stress and the imposed constant strain rate, which can be varied between 10-6 and 4 ⋅ 10-5 s-1. The two-dimensional temperature distribution of the glass confining side walls is measured with a thermal infrared camera and is proportional to the temperature distribution within the model. Deformation of the isotherms can thus be monitored during the experiment. By scaling down linear dimensions by a factor of 106 time by 1010, viscosity by 1016 and temperature by 10, we obtain a consistent set of scaling factors. This allows geometrical, kinematic, dynamic, and rheological similarity with lithospheric processes to be attained.