Present-day stress field and deformation in eastern Austria

We analysed fault plane solutions and borehole breakouts in the eastern par t of the Eastern Alps and found a heterogeneous stress field which we inter pret as a transition zone of three different stress provinces: the western European stress province with NW to NNW S-H Orientation and mainly strike-s lip faulting regime; the Adriatic stress province with a radial stress patt ern and thrust faulting to strike-slip faulting regime; and the Dinaric-Pan nonian stress province with NE S-H orientation and strike-slip faulting reg ime. The western Pannonian basin seems to be a part of the transition zone with WNW to NW S-H orientation. A stress regime stimulating strike-slip fau lting prevails in the Eastern Alps, The south Bohemian basement spur as a m ajor tectonic structure with a high rheological contrast to surrounding uni ts has a strong influence on the stress field and exhibits the highest seis micity at its tip due to stress concentration. From a constructed vertical stress orientation profile we found stress decoupling of the Northern Calca reous Alps from the underlying European foreland. Both the Molasse and the Flysch-Helvetic zone are considered as candidates for decoupling horizons d ue to stress orientation observations and due to their rheological behaviou r. From seismological and rheological data, we suggest a horizontal stress decoupling across the Eastern Alps caused by a weakened central Alpine lith osphere.