Geodetic evidence for a low slip rate in the Altyn Tagh fault system

The collision between India and Asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east Asia. Geological slip-rate estimates of 20–30 mm yr-1 suggest that the largest of these faults, the 2,000-km-long Altyn Tagh fault system on the northern edge of the Tibetan plateau, absorbs as much of the Indo-Asian convergence signal as do the Himalayas1,2—partly by oblique slip and partly by contraction and mountain growth3,4,5. However, the predictions of dynamic models for Asian deformation6 and the lower bounds of some geological slip-rates estimates (3–9 mm yr-1; refs 7, 8) suggest that the Altyn Tagh system is less active. Here, we report geodetic data from 89–91° E that indicate left-lateral shear of 9 ± 5 mm yr-1 and contraction of 3 ± 1 mm yr-1 across the Altyn Tagh system. This result—combined with our finding that, at 90° E, Tibet contracts north–south at 9 ± 1 mm yr-1—supports the predictions of dynamic models of Asian deformation.