Active Deformation of Asia: From Kinematics to Dynamics

Using estimated strain rates across the actively deforming region of Asia to infer variations in viscous stress, it is shown that gradients of stress point uphill toward the center of Tibet, where gravitational potential energy per unit surface area reaches a maximum. Thus, the dynamics of the deformation seem to obey the equation of creeping flow, which expresses a balance between gradients in stress and the gravitational body force. This balance, in the region of the Tibetan plateau, yields an estimate of 10 22 pascal second for the average viscosity of the Tibetan lithosphere, which is only about 10 to 100 times greater than the viscosity of the convecting upper mantle.