| The collision between two continental plates is a complicated multi-stage process. To understand the whole process of the collision it is important to first understand the most recent episode of the collision of the Indian with the Asian plate and to determine the rheology of this region.;I present a technique based on the "spherical" Earth with "real" spherical finite elements and spherical fault finite elements, in which vector nodal functions are used to interpolate the velocity at any point in a spherical element from the values at the nodes. After passing a lot of different tests, this computer program is ready for modeling tectonic deformation and fault motion in any large region.;The models cover all of Asia east of 40;The best model matches 94% of fault slip senses, with 2.4 mm/a RMS error in fault slip rate. The best fitting parameters are fault friction of 0.085 ;The low level of deviatoric stresses suggests that topographic stress plays a major role in the orogeny; thus, we have to expect that different paleotopography was a major factor causing the multiple stages of the collision. By calculating models with different elevations of Tibet, I find that when the average elevation was 2000 m, extrusion was achieved by motion along strike slip faults and the extrusion rate was only half of the crustal thickening rate. After Tibet rose the primary mechanism of extrusion changed to rigid motion of crust with thickness gradients. |
