Identifying Seismic Anisotropy Patterns and Improving Tomographic Images in the Alps and Apennines Subduction Environments with Splitting Intensity 

Abstract

<p>Active and past subduction systems influence the interpretation and understanding of current tectonics and velocity structures of the upper mantle of the Alps and Apennines. Computational advances over the years made it possible to identify remnant and active slabs up to great depths. SKS splitting measurements revealed mostly clockwise rotation in the Alpine region and mostly splitting parameters parallel to the Apennines (with new measurements in Central Italy). More than 700 stations were used in this study to calculate splitting intensities and with those similar but more stable fast polarization directions were recovered compared to SKS measurements. Splitting intensity measurements support a possible mantle material flowing through a tear in the Central Apennines. In the Po Plain region as well as east of the Apennine mountains anisotropy seems to be weaker. Moreover the complexity of layered anisotropy, upper mantle flow through possible slab detachments, and subduction related anisotropy with a dipping axis of symmetry are difficult to recover. Due to directional dependency of splitting intensity measurements, they can be used in tomographic inversions to get depth dependent horizontal anisotropy. So far we are able to recover the most prominent splitting patterns and see some changes with depth, especially for anisotropic strength. In this study we intend to use our results to improve tomographic images of the upper mantle by mapping and comparing existing and new anisotropy measurements (e.g., SKS, Pn anisotropy, azimuthal anisotropy from surface waves tomography, and splitting intensities).</p>