New constraints on current deformation in Asia from continuous GPS measurements at Ulan Baatar, Mongolia

Calais, E., and S. Amarjargal, New constraints on current deformation in Asia from continuous GPS measurements at Ulan Baatar, Mongolia, Geophys. Res. Letters, 27, 1527-1531, 2000.


Using GPS data continuously recorded at a permanent site in Ulan Baatar (Mongolia) between 1995 and 1998, we find a velocity 6.4±1.6 mm/yr in a N125±30° azimuth with respect to Eurasia. This result, together with the GPS-derived velocity at other sites in northern China, indicates eastward motion of the Amuria/North China block at 6-10 mm/yr relative to Eurasia.

The small differential motion between the Amuria/North China and South China blocks  implied by these geodetic results (less than 5 mm/yr) is difficult to reconcile with the geological rates of 10-15 mm/yr found on some of the major strike-slip faults that separate these two blocks. The velocity of the Amuria/North China block relative to Eurasia does not agree with a model where eastward translation of a rigid south China block dominates, that requires a faster velocity for south China and slower velocity for north China, but are in better agreement with models where crustal thickening dominates lateral extrusion.

The current motion of the Amuria/North China block is significantly faster than the predictions of deformation models of Asia that assume full coupling in the India/Eurasia collision zone, zero-coupling along the Pacific subductions, and neglect gravitational forces. This suggests that the India/Eurasia collision is not the only process currently driving deformation in Asia, but that other mechanisms, such as far-field contribution of subduction processes and gravitational forces may also significantly contribute to intracontinental deformation.