Active tectonic deformation at the transition from the European and Pannonian domain monitored by a local GNSS network

Tectonic processes which led to the generation of the Alps, Carpathians, Dinarides, and the Pannonian basin are still on work. In particular they affect the transition zone from the European platform over the Eastern Alps to the Pannonian basin. GPS network solutions confirm the ongoing lateral extrusion of East Alpine crustal blocks directed to the Pannonian basin. Earthquakes and neo-tectonic deformations are concentrated along NE-SW oriented sinistral strike-slip faults (Mur-Mürz faults and Vienna transfer fault system). This area is the target of ALPAACT (Seismological and geodetic monitoring of ALpine-PAnnonian ACtive Tectonics). The geodetic monitoring of active tectonics in this area is realized by a local GNSS network, which extends from the Bohemian Massif in the north to the Styrian basin in the south and spreads out over the active fault zone. The total of 23 stations belongs either to the IGS network or to regional RTK-positioning services (ÖBB, Wien-Energie, BEWAG, EVN). So far GNSS observation data from the years 2007 and 2008 were reprocessed using the Bernese software 5.0 and precise orbits. The solution is tied to the ITRF2000 by three IGS stations. For a geodynamic interpretation the velocities are referenced to the station Graz-Lustbühel (GRAZ). The individual velocity vectors scatter considerably and a systematic trend cannot be recognized directly. The mean velocity of the stations south of the Mur-Mürz valley and the Vienna basin transfer fault system, relative to the stations located in the north, amounts to 1.1 mm/year. Its orientation is about NE (azimuth = 55°). This result fits nearly perfectly the prediction of a kinematic model which was derived from the structure of the lithosphere and calibrated by regional geodetic deformation models. Due to the low relative velocities and the short observation period, these results should be considered as preliminary. Hence efforts will be made to achieve a geodetic monitoring over a time period of ten years.