Crustal velocity field of western Europe from permanent GPS array solutions, 1996-2001

Abstract

We derive a new geodetic velocity field for western Europe and the Western Mediterranean by rigorously combining (1) a selection of 36 ITRF2000 sites, (2) a solution from a subset of sites of the European Permanent GPS Network (EUREF-EPN), (3) a solution of the French national geodetic permanent GPS network (RGP) and (4) a solution of a permanent GPS network in the western Alps (REGAL). The resulting velocity field describes horizontal crustal motion at 64 sites in Western Europe with an accuracy of the order of 1 mm yr-1 or better. Its analysis shows that Central Europe (defined as east of the Rhine Graben and north of the Alps and the Carpathians) behaves rigidly at a 0.4 mm yr-1 level and defines a stable Europe reference frame. In that reference frame, we find no significant motion at sites located west of the Rhine graben and on the Iberian peninsula, which sets an upper bound of 0.6 mm yr-1 on horizontal motion across the Rhine graben and the Pyrenees. We find that the current strain pattern in the western Alps combines E-W extension and right-lateral shear. We confirm a counterclockwise rotation of the Adriatic microplate, which appears to control the strain pattern along its boundaries in the Friuli area, the Alps and the Apennines. Our results also suggest that the Africa-Eurasia plate motion in the Western Mediterranean may be 40 50 per cent slower that the NUVELIA plate motion model and rotated 20 30 counterclockwise.