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We establish a continuous GPS transect crossing the central Altyn Tagh fault at 90°E with eight years of observations. GPS velocities along this profile and another one crossing the fault at 86°E suggest a fault slip rate of 12.4 ± 0.7 mm/yr, but with asymmetric straining of adjacent terrain. On the south side, ∼8.2 mm/yr of left‐lateral shear is absorbed across a region ∼210 km from the fault, but only ∼4.2 mm/yr is found on the north side. This estimate of slip rate is ∼30% larger than the consensus estimate of previous models. By treating the deforming regions as elastic plates with different thicknesses overlying a substrata that obeys a linear Maxwell viscoelastic constitutive relationship, we infer a viscosity of ∼5.1 × 1019 Pa s (between 3.5 and 9.1 × 1019 Pa s at 1‐σ) on the south side, beneath northern Tibetan Plateau. This low viscosity, compared to some estimates for the asthenosphere, concurs with the Tibetan Plateau being underlain by a relatively hot and weak lower crust and upper mantle. The effective elastic thickness on the south side is 16.5–20 km, which is significantly smaller than that of the Tarim Basin of >60 km. Plain Language Summary: Markedly asymmetric interseismic deformation is observed across the Altyn Tagh fault, revealing differing lithospheric rheology across the fault between northern Tibet and the Tarim Basin. We invoke a 2‐dimensional viscoelastic deformation model to interpret the GPS velocity field across the central Altyn Tagh fault and find that the deformation field is well explained by viscoelastic deformation of the lower crust and upper mantle, underneath a thin elastic layer (∼17.5 km thick) for the northern Tibet and Qaidam Basin and a thick elastic layer (>60 km thick) for the Tarim Basin, respectively. The inferred effective viscosity of ∼5.1 × 1019 Pa s for northern Tibet lithosphere substrate is similar to that beneath other regions with thin lithosphere in the world. Characterization of the rheological structure of the Tibetan plateau and its boundary faults helps understanding dynamic processes of the plateau lithosphere and the continental lithosphere at large. The estimated long‐term slip rate of ∼12 mm/yr for the central Altyn Tagh fault is ∼30% higher than the consensus estimate of previous geodetic studies, which has a significant implication for the assessment of seismic hazard for the northern rim of the Tibetan plateau. Key Points: Asymmetric interseismic deformation across Altyn Tagh fault reveals differing lithospheric rheology between northern Tibet and TarimViscosity of 5.1 (+4.0/–1.6)×1019 Pa s for lower crust and upper mantle of northern Tibet and Qaidam is similar to that beneath regions of thin lithosphereEffective elastic thickness of northern Tibet and western Qaidam Basin (16.5–20 km) is notably thinner than that of Tarim Basin (>60 km) [ABSTRACT FROM AUTHOR]

Global positioning system velocities from 553 control points within the Tibetan Plateau and on its margins show that the present-day tectonics in the plateau is best described as deformation of a continuous medium, at least when averaged over distances of >∼100 km. Deformation occurs throughout the plateau interior by ESE-WNW extension and slightly slower NNE-SSW shortening. Relative to Eurasia, material within the plateau interior moves roughly eastward with speeds that increase toward the east, and then flows southward around the eastern end of the Himalaya. Crustal thickening on the northeastern and eastern margins of the plateau occurs over a zone ∼400 km wide and cannot be the result of elastic strain on a single major thrust fault. Shortening there accommodates much of India's penetration into Eurasia. A description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field. [ABSTRACT FROM AUTHOR]

By combining terrace riser offsets with terrace ages dated by 14C, optically stimulated luminescence (OSL), and 10Be techniques, we determine average slip rates of 1.1 ± 0.3 mm/yr and 1.2 ± 0.4 mm/yr for the Elashan and Riyueshan faults, two northnorthwest-- trending, right-lateral, strikeslip faults west and east of the lake Qinghai in the northeastern margin of the Tibetan Plateau. These faults are conjugate to the major easterly trending, left-lateral Altyn Tagh, Haiyuan-Qilianshan, and Kunlun faults, and they contribute to the subdivision of the region between the Haiyuan- Qilianshan and Kunlun faults into small blocks tens to ~100 km in dimension. The rela tively low slip rates in this region reflect distributed deformation. The total rightlateral offsets of geological contacts are ~9-- 12 km along the Elashan fault and ~11--12 km for the northern segment of the Riyueshan fault. If long-term slip rates were constant during late Cenozoic time, dates of initiation of dextral movement would be 9 or 10 ± 3 Ma for the two strike-slip faults, concurrent with onsets or acceleration of tectonic deformation in Cenozoic basins nearby. Our study highlights a stage of tectonic deformation in the northeastern margin of the Tibetan Plateau beginning since ca. 8--12 Ma, tens of millions of years after the collision between India and Eurasia began. [ABSTRACT FROM AUTHOR]