During my diploma thesis we addressed some of the open questions pertaining to stress modeling. These range from issues as fundamental as why it remains necessary to isolate the lithosphere from mantle flow in models of plate dynamics, to specific questions concerning regional stress patterns.
In the case of the Eurasian plate one would like to know if the collision with India is responsible for extensional tectonics in the region of Lake Baikal, how in China compression can be aligned east-west when we would expect trench suction to lead to extension along that axis and if the Eurasian plate is a single unit or rather made up of smaller plates. In Western Europe itself it is not clear why stress directions trend NW-SE when many models presented in scientific literature predict them to be roughly east-west, and why the same area experiences not only compressional tectonics as expected from its setting between ridge push and Alpine collision, but also normal and strike-slip faulting.
Our models of the Eurasian plate concentrate on the importance of rheology and lateral strength variations for lithospheric stress patterns which is a step ahead from previous purely elastic models of the Central European stress field. Moreover, they do not artificially remove the influence of the Eurasian plate which lies east of the Ural range as has been done frequently based on the assumption that the presence of the East European platform permits such a simplification. By investigating the influence of lateral strength contrasts such as cratons on stress trajectories we can test whether this approach is indeed justified or not.

The analysis of our modelling provides strong evidence that the implementation of plasticity is the prerequisite for a good stress model of Eurasia. Our best model can account for the observed directions of maximal horizontal compression and for stress levels in the Eurasian plate. It also predicts a reasonable distribution of strain rates, but is inadequate when it comes to forecasting the deformation velocities.
Interestingly, a power law rheology with appropriately chosen parameters seems to have very similar effects on the outcome of the stress pattern and it thus also appears to be suited for the task. Whether this is result of the geometry of the Eurasian or a should be resolved by further simulations but we believe that realistic models of continental lithosphere require the application of some kind of nonlinear rheological behaviour and/or damage rheologies. For models of the more rigid oceanic lithosphere on the other hand, an elastic rheology might suffice.


A detailed description of our modelling efforts and of our findings can be found here:

• 'Dynamics of the Eurasian Plate' (diploma thesis)
  
  M. Sargent (supervision by S. Goes & G. Morra), 2004, ETHZ

  Download (4.5 MB):

  
  
• 'A dynamical model for generating Eurasian lithospheric stress and strain rate fields: Effect of rheology and cratons'
  
  Hieronymus, C. F., Goes, S., Sargent, M. T., Morra, G., 2008, J. Geophys. Res., 113, B07404

Related Links & Literature:

• Collaborators: Saskia Goes, Gabriele Morra, Chris Hieronymus
• The Institute of Geophysics at the ETH Zürich
• The World Stress Map Project
• 'On the Relative Importance of the Driving Forces of Plate Motion'
  
  Forsyth & Uyeda 1975, Geophys. J. R. astr. Soc., 43, 163
• 'The effect of plate stresses and shallow mantle temperatures on tectonics of northwestern Europe'
  
  Goes et al. 2000, Global Planet. Change, 27, 23
• 'Origin of the lithospheric stress field'
  
  Lithgow-Bertelloni & Guynn 2004, JGR, 109, 1408
• 'The generation of plate tectonics from mantle convection'
  
  Bercovici, D. 2003, EPSL, 205, 107