Active Seismotectonic Deformation in Front of the Dolomites Indenter, Eastern Alps

We use earthquake focal mechanisms to study present‐day deformation and stress in the western part of the Eastern European Alps. We define the following regions, based on seismicity and kinematically compatible focal mechanism types: (1) the northern and western parts of the Dolomites indenter, the western and central Tauern Window, and the northern Alpine margin and foreland lack significant seismicity. (2) The indenter boundaries are characterized by strike‐slip faulting. Based on earthquake and geodetic data, the western and northern indenter boundaries are active sinistral and dextral strike‐slip/oblique slip faults. (3) West and north of the indenter corner, we observe normal and strike‐slip faulting in an up to 70 km‐wide zone. From west to east, the minimum horizontal stress rotates clockwise about 10–20°, from NE to ENE. (4) North of (3), east of the Swiss/Austrian border, we find evidence for N to NNW directed thrust faulting, and local orogen‐parallel extension. From our results and geodetic data, we infer that relative to a fixed northern foreland, NNW directed indentation is transferred at depth via the Sub‐Tauern thrust system to this 100‐km‐wide zone of localized thrusting. A lack of evidence for major, active strike‐slip faulting north of the Tauern Window is in line with geodetic data, which show no significant velocity difference between the northern part of the Eastern Alps and their foreland. Key Points We calculate 162 new focal mechanisms for the western and central Eastern Alps. Earthquakes and mechanisms only partially fit with mapped surface faults Stress orientation is deflected by 10–20° in a 70‐km‐wide zone around the boundaries of the Dolomites indenter Part of the Europe‐Adria convergence is transferred to a 100‐km‐wide, seismically active thrusting zone 30 km north of the indenter corner