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

On the basis of 3 years of continuous GPS measurements (1995-1998) show a velocity of 6.4+/-1.6 mm/yr in a N125+/-30 degrees azimuth with respect to Eurasia at a permanent site in Ulan Baatar, Mongolia. Together with recent GPS results in Asia, this result indicates motion of the Amurian/North China block at 6-10 mm/yr to the east to southeast relative to Eurasia, 0 to 5 mm/yr slower than south China (10-11 mm/yr eastward). The small differential motion between these two blocks is in agreement with deformation models of Asia where crustal thickening dominates lateral extrusion. The fact that the velocity of the Amurian/North China block is significantly faster than the predictions of models based on the hypothesis that deformation in Asia is enterely driven by the India/Eurasia collision suggests that other mechanisms, such as far-field effects of subduction processes and gravitational forces could significantly contribute to intracontinental deformation.