Geodetic and seismic constraints on contemporary deformation on the northeastern Tibetan plateau: Velocity and strain rate tensor analysis

Abstract

The study of the velocity and strain rate of the northeastern Tibetan Plateau can explain its crustal deformation characteristics. Previous investigations have relied on mathematical interpolation in GPS velocity to obtain a continuous strain field; these approaches can be applied well to regions where the deformation is relatively smooth and are not entirely suitable for the northeastern Tibetan Plateau that is cut by several large strike-slip faults. Thus, this study incorporates seismic constraints into the GNSS velocity and strain analysis to obtain a more realistic deformation field and compares it with the uplift rate and the stress results in depth, it will provide a comprehensive view of contemporary deformation on the northeastern Tibetan Plateau. It shows that there are two prominent deforming zones localized on the middle segments of the Haiyuan and East Kunlun faults, which may result from the different strengths in fault segmentation. The velocity and strain rate in the four profiles show that the convergence strain obviously decay from ∼15.5 mm/yr and ∼ 15.48 nstrain/yr in the western Qilian Mountains to ∼5.73 mm/yr and ∼ 5.76 nstrain/yr in the eastern Long Zhong Basin, respectively. The comparison between the vertical uplift rate, SKS result, and strain rate field indicates that the northeastern Tibetan Plateau is not only dominated by crustal shortening corresponding to the topography and surface fault geometry, but also by the strain transfer of motion along these significant strike-slip faults accounting for the extrusion and growth of the Tibetan Plateau. Combined with recent seismological results, our results indicate that the deformation of the study region resembles that of the Tibetan Plateau and can be viewed as a combined process linking both NE- or NEE-directed crustal shortening, vertical uplift, lateral extrusion along strike-slip faults and partial melting or mantle upwelling at depth.