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We present a set of three-dimensional models of the upper mantle-lithosphere system for a simplified geometry of the Eurasian plate. A major difficulty of matching the stress and the strain rate fields simultaneously derives from the inclusion of tectonically active regions within the model domain. For typical elastic, viscous, or plastic rheologies, high stress levels are required in order to produce realistic convergence rates between India and Asia. Our models show robustly that such stresses are transmitted throughout most of the plate, dominating locally generated stresses even in distal regions such as Europe in a manner that is not compatible with observations. Cratons with roots that extend deep into the mantle are unable to provide a significant stress-shielding effect unless the viscosity contrast between the asthenosphere and the underlying mantle is around 100 or greater.
A damage rheology for the lithosphere with history-dependent behavior and material softening by a viscosity reduction of several orders of magnitude is shown to eliminate this conundrum. Continental convergence at high velocity but low stress is facilitated by the formation of long-lived shear zones similar to those observed north of the Himalayas.
The low stress associated with the collision, together with the decoupling effect of the shear zones causes the distal stress field in Europe to be controlled by the effects of the neighboring boundaries in agreement with observations.
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