Modelling of current crustal tectonic deformation in the Chinese Tianshan orogenic belt constrained by GPS observations

摘要

It is important to discover the deformation characteristics of the Tianshan mountain range for a better understanding of the geodynamics of the Tianshan orogenic belt. Constrained by the GPS-derived velocity vectors of crustal movement, the current velocity field, stress field and strain rate in the Tianshan mountains have been retrieved from a three-dimensional numerical model presented in this paper by using the finite-element code ANSYS, on the basis of geological structures, tectonic regimes, active fault belts and seismic velocity structures of the crust and upper mantle. The results suggest that: (1) the general direction of crustal movement is NNE, and yet gradually turns to NE from west to east; (2) the regional stress field is characterized by near N-S tectonic compression, resulting in crustal shortening in the near N-S direction as well; and (3) the shortening strain rate is ～10-8 a-1 and decreases gradually from west to east. Our results support the opinion that the crustal deformation of the Tianshan mountain range is controlled by the clockwise rotation of the Tarim basin.