Geodetic constraints on the rigidity and relative motion of Eurasia and North America

GPS observations in northeastem Asia, when combined with observations from the global network for the period 1992-1999, yield an angular rotation vector between Eurasia and North America consistent with and a factor of two more precise than estimates derived using GPS or VLBI data previously available from only western Eurasia. The new vector implies a pole of relative rotation 1200 km more to the northwest than predicted by the NUVEL-1A global plate model, suggesting a significant change in the relative motion of Eurasia and North America over the past 3 Myr. The standard deviations of horizontal velocities from rigid plate motion for nineteen stations in Eurasia and ten in North America are less than 1 mm/yr; the observations place an upper bound of 2 mm/yr at 95% confidence for relative motion between western and eastern Eurasia.