Imaging the Alpine Collision With Seismic Radial Anisotropy

Abstract The Alpine region and the adjacent Northern Apennines (NA) and Northern Dinarides record the complex tectonic evolution associated with the collision between the Eurasian and Adriatic plates. We combine Rayleigh and Love surface waves from ambient noise and earthquake data recorded at over 3,300 seismic stations to construct a high‐resolution 3D model of shear‐wave velocity and radial anisotropy of the crust and upper mantle down to 250 km depth (AlpRA25). The model reveals pronounced spatial variations in that reflect the complex collisional dynamics between the two plates. Within the crust, negative radial anisotropy is associated with steeply dipping fabrics and fault zones in the hanging wall of the Alpine and Apenninic deformation fronts and with the Eurasian–Adriatic plate interface. The so‐called negative anisotropy is also present near the Ivrea body and in the oceanic crust and uppermost mantle of the Ligurian Sea . In contrast, the Eurasian lower crust throughout the Alps, and the lower Adriatic crust and the upper Tyrrhenian crust, in the NA, exhibit strong horizontal anisotropy . The Adriatic slab beneath the NA is characterized by pronounced negative radial anisotropy , while in the mantle domains located between the slabs, radial anisotropy remains dominantly positive . By combining shear‐wave velocity and radial anisotropy, AlpRA25 provides new constraints on crust–mantle coupling, slab geometry, and deformation styles across the Alpine–Apennine system, demonstrating the value of radial anisotropy as a diagnostic proxy for lithospheric and asthenospheric deformation.