Geodynamic processes in the Earth cause deformation of rocks. This deformation can align mineral crystals, which leads to physical properties depending on direction of the waves propagate – which is known as “anisotropy”. The effect on shear waves is to split them into two orthogonal phases which travel in different velocity, defining a fast and a slow phase – analogous to optical birefringence of polarized light. The same happens for seismic waves that travel through the Earth, which also consists of anisotropic rocks. A seismic wave splits into two, fast and slow, phases that arrive at the seismic station (at the surface) at different times. The orientation of the faster phase, called “fast orientation”, and the delay time between fast and slow phase thus allow us to describe the anisotropy in the interior of the Earth.  
We have measured anisotropic parameters under the Eastern Alps at the scale of the upper mantle – using data recorded at seismological stations in Austria, Slovenia, and northern Italy. Our results, together with earlier results for the Western Alps, show a spectacular deformation pattern that is roughly aligned with the trend of Alpine mountain chain (see the fast orientations in figure). This is one the clearest examples yet of mountain chain-parallel anisotropy worldwide. This new finding has received great interest of geologists and geophysicists, who wish to complete the surface-geological picture of mountain chains with information at depth – where the drivers of geodynamic processes are probably located. This new piece of information will help answer fundamental questions about the geodynamics of the Alpine chain (see the recent EPSL papers:  Bokelmann et al., 2013, doi:10.1016/j.epsl.2013.09.019, and Qorbani et al., 2015, doi:10.1016/j.epsl.2014.10.049 ).