Present-day and Holocene horizontal movements on the Baikal geodynamic test ground

In the framework of the Russian-French project, a series of geodesic statio ns for studying present-day crust deformations by the GPS method was organi zed on the Baikal geodynamic test ground. Processing of data of 3-year-long observations permitted obtaining a field of vectors of the rates of presen t-day horizontal movements in the southern and central parts of the Baikal Rift System. The authors have established the absence of dislocations from the internal field of the Siberian Platform and a concordant southeastward shift of bench marks in West Transbaikalia. The major parameters of the vec tors do not contradict the dislocations predicted by structure-geological a nd seismological data. On the basis of direct instrumental measurements mad e in 1994-97, it has been first established that the opening of the Baikal Rift occurs at an average rate of 4.5+/-1.5 mm/year toward 100 degrees N. T he directions and rates of horizontal block displacements in the south of t he Baikal Rift System in the Holocene are in agreement with the GPS data. I n the central part of the rift, the expansion of blocks in the Holocene occ urred toward 130 degrees N, and between the blocks of East Sayan and the Si berian Platform oblique divergent movements toward 100 degrees N took place .