[1] We present new geodetic results of crustal velocities over a large part of northern Asia based on GPS measurements in the Baikal rift zone and Mongolia spanning the 1994-2002 period. We combine our results with the GPS velocity field for China of Wang et al. [2001] and derive a consistent velocity field for most of Asia. We find contrasted kinematic and strain regimes in Mongolia, with northward velocities and N-S shortening in westernmost Mongolia but eastward to southeastward motion and left-lateral shear for central and eastern Mongolia. This eastward to southeastward motion of central and eastern Mongolia is accommodated by left-lateral slip on the E-W trending Tunka, Bolnay, and Gobi Altay faults (2 ± 1.2 mm yr À1 , 2.6 ± 1.0 mm yr À1 , and 1.2 mm yr À1 , respectively) and by about 4 mm yr À1 of extension across the Baikal rift zone. Consequently, $15% of the India-Eurasia convergence is accommodated north of the Tien Shan, by N-S shortening combined with dextral shear in the Mongolian Altay and by eastward displacements along major left-lateral strike-slip faults in central and eastern Mongolia. We find a counterclockwise rotation of north and south China as a quasi-rigid block around a pole north of the Stanovoy belt, which rules out the existence of an Amurian plate as previously defined and implies <2 mm yr À1 of left-lateral slip on the Qinling Shan fault zone.

Summary GPS measurement campaigns in the Mongolia–Baikal area show that: (1) the Baikal rift zone is currently opening at 4–5 mm yr−1 in a NW–SE direction and (2) the western part of the Amurian–north China block is moving eastward relative to Eurasia at 5–7 mm yr−1. These results are consistent with recent geodetic studies in Asia, and indicate that crustal motions in Mongolia and north China derived from geodetic measurements are significantly faster than those proposed by most deformation models of Asia. Using a numerical model, we test whether post‐seismic deformation caused by viscoelastic relaxation in the lower crust following the Tsetserleg–Bolnay earthquake sequence (Mw= 7.9 and 8.4, 1905 July) can explain this discrepancy. We find that surface velocities at the GPS sites presented here for the 1997–2000 time period can reach 4 mm yr−1, depending on the earthquake source parameters and the rheology used in the models. Using a model based on our best current knowledge of lithospheric structure and rheology in the Mongolia–Baikal area, we find that the contribution of post‐seismic effects to the GPS velocities presented here is less than 2 mm yr−1 for the Mongolian sites and less than 1 mm yr−1 for the Baikal sites. We therefore conclude that the post‐seismic effects of the Mw= 8.4, 1905 Bolnay earthquake cannot explain why the GPS‐derived crustal motions in Mongolia and the Baikal rift zone are significantly larger than those proposed by deformation models of Asia. This discrepancy must therefore be sought in processes not accounted for in most of these deformation models, such as the far‐field contribution of the Pacific subduction zones and/or the effect of gravitational forces on intracontinental deformation.

Abstract. On the basis of 3 years of continuous GPS measurements (1995)(1996)(1997)(1998) show a velocity of 6.4+_1.6 mm/yr in a N125+_30 ø 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.