Present-day slip-rate of Altyn Tagh Fault: Numerical result constrained by GPS data

摘要

Geological and seismic evidence suggests that nearly two thirds of the convergence between India and Eurasia is accommodated by the crustal deformation of Asia. Two competing mechanisms were proposed to describe this accommodation: distributed crustal thickening and lateral extrusion along main faults. The kinematics of the Altyn Tagh Fault (ATF) is critical in determining the relative importance of these two mechanisms, inasmuch as the ATF slip-rates predicted by hypotheses of these competing mechanisms are very different. Using a finite element formalism to construct a thin-sheet model, we seek a velocity solution approaching the current kinematics of the ATF. The GPS data in the Tibetan Plateau and neighboring regions are employed as constraint conditions, in successive steps. The predicted velocity distribution near the ATF fits well to the observations, with overall standard deviations of 2.3 mm/yr and 2.8 mm/yr for the northward and eastward components, respectively. The inferred average slip-rate of the ATF is (7.4 ± 1) mm/yr, with some variation along the fault. The slip-rate estimate of the ATF reported in this paper supports the distributed crustal thickening hypothesis for the crustal deformation of the Tibetan Plateau.