Large-scale strain-rates in Europe derived from observations in the European geodetic VLBI network

Abstract

Since 1990 the European fixed station geodetic Very Long Baseline Interferometry (VLBI) network has been observing on a regular basis in order to determine surface motion in Europe. During the first years the network was limited to central and southern Europe. With the inclusion of Ny- ˚ Alesund on Spitsbergen and Simeiz on the Crimean peninsula it received valuable extensions to the north and to the east. Today more than 11 years of observations allow the determination of surface motion in Europe with high accu- racy. Baseline measurements between the European geodetic VLBI stations are achieved with an accuracy of better than 2 mm, plus a baseline dependent term of less than one part per billion. Topocentric displacements of the European geodetic VLBI stations are determined with respect to a cen- tral reference station. These results show evidence for hori- zontal deformation due to post-glacial rebound in the north- ern part of the network. In the southern part of the network the results for horizontal motions display the complex evo- lution of the Apennines system. The vertical deformations detected in the northern part exceed the predictions due to post-glacial rebound. The subsidence at the station Medicina can be explained by a combination of tectonic processes and man-made influences. The uplift detected at Madrid has no explanation yet, while the other stations do not show signifi- cant vertical motion. Using the derived topocentric displacements, strain-rates in Europe are determined on a large-scale. The results show strain-rates with maximal values of 5.5 ppb/yr which are sig- nificantly smaller than those that have been observed in the eastern Mediterranean area. In the Alpine region compres- sional strain-rates are observed.