Illuminating the Complex Structural Fabric Beneath the European Alps

Source: Journal of Geophysical Research: Solid Earth

The present-day structure of the European Alps is created by subduction and continental collision processes involving several plates and micro-plates. To better understand the dynamics of this complex region, the structural fabrics generated within the plates by the collisions, and the interaction with ongoing mantle flow beneath the plates, Link and Rümpker [2023] present a comprehensive analysis of seismic anisotropy across the region. Anisotropy is created by mineral alignments associated with dynamic processes within the crust and mantle, and manifests as a change in seismic wave speed with direction. It can be measured via analysis of the observed splitting of incoming shear seismic waves recorded at seismographs on the surface.

The authors measured shear-wave splitting of almost 600 seismographs distributed across the entire region of the European Alps, with an average station spacing of less than 30 kilometers. This impressive dataset allows for a detailed analysis that highlights not only the intricacies of the spatial variations in anisotropy across the region, but also the variations with depth, which are often difficult to discern. The authors infer distinct layering, showing the relative contributions of tectonic deformation within the plate and active mantle flow beneath. The results are important to advance our understanding of the complex history of the Alpine collision, and the dynamics of the surrounding Mediterranean region.