Deformation of the South-Eastern Baltic Shield from GNSS observations

The Pulkovo observatory is situated in a unique geological setting. Within only 300 kilometres from Northern Karelian Isthmus to a few kilometres south from the observatory the Archean, Paleo and Neoproterozoic, Cambrian, Ordovician, Devonian, and Carboniferous rocks are sequentially surfacing. Thus these 300 kilometres in distance correspond to 3 billion years in geologic time. The city of St. Petersburg marks a transition zone from the Baltic Shield to the East European Platform, and the observatory is built on the Baltic Klint that in turn marks a transition from Ediacaran to Devonian. Such a rich geological constitution of the region summons a need for geodynamical studies. The authors have recently gathered the GNSS observations available in the region from 1993 until present, including those made by the authors, with permanent and high quality field GNSS stations. These measurements were processed with the GIPSY software using the PPP strategy. The resulting coordinates were then adjusted for atmospheric loading corrections, and station velocities were computed. The station velocities were then used for estimation of the regional deformation field. The resulting deformation field shows a weak meridional compression and possibly a slow counterclockwise rotation of the Baltic shield with respect to the East European platform.