Present-day stress field, strain rate field and seismicity of the Pannonian region: overview and integrated analysis

We present an overview of recent findings on the seismicity, stress field and strain rate field of the Pannonian region. We furthermore show new inferences for deformation mechanisms and lithospheric rheology via an integrated analysis of the datasets. The NNW motion of the Dinarides and the opposite, SW motion of the east and south Carpathians induce shortening in the western and central Pannonian Basin while leading to regional shearing around the basin's SE boundary. This induces moderate seismic activity related to strike-slip and reverse faulting. The maximum horizontal stress and geodetic shortening directions generally agree, implying that upper crustal stresses and surface deformation correspond to the same forces. 2D rheological models confirm that the shallow upper crust is the only brittle layer in the Pannonian lithosphere, while the brittle–ductile transition zone could be as shallow as 6–9.5 km in the Danube Basin. Comparison of seismic moment rates and moment rate predictions from geodetic strain rates show that deep Pannonian sub-basins accumulate major seismic deficits. This could be explained by dominantly aseismic deformation of the weak upper crust, as supported by a comparison with case studies from different geodynamic environments. Stronger mountainous regions in the study area show no to moderate seismic deficits.