DOI: 10.5176/2335-6774_1.1.10
Authors: LU Shikuo
Abstract:
On the assumption that the GPS（Global Positioning System）velocity field is affected by the interseismic elastic
deformation of the upper crust to a great degree, under the constraint of the existing GPS data, by the numerical simulation method we construct the viscoelastic mechanical models to analyse the rationality of the explanation to the Tibetan present-day crustal movement by the two different deformation mechanisms in the deep continental lithosphere, such as the viscous flow in the lower crust and the shear strain localization in the deep fault zones, in this paper. Numerical experimentsshow that the present-day crustal movement in the different regions of the Tibetan plateau may be attributed to the different geodynamic mechanisms. In the Tibetan southeastern area, although the shear strain localization in the deep fault zones could not be rejected, the viscosity of the lower crust should be much lower in order to diminish the model’s prediction error. In the central-northern and northeastern areas of the Tibetan plateau, the GPS velocity field is interpreted much better by the shear strain localization in the deep fault zones, implying that the actual active faults may incise down deeply in these areas. Ignoring the lateral change of the viscosity in the lower crust, the preferred model by which the GPS velocity field could be accounted for with a first-order similarity yields an estimate of 1022—5×1022Pa·s for the mean viscosity of the Tibetan lower crust, and an estimate of about 1021Pa·s for that of the deep fault zones. Due to the high elevation and the lower viscosity of the lower crust, the gravity plays an important role on the present-day movement of the Tibetan plateau.
Keywords: ductile flow in the lower crust, GPS data, numerical experiment, shear strain localization in deep fault zones, Tibetan plateau
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