Crustal and Upper Mantle Three-Dimensional Stratification and Anisotropy from Receiver Functions (Northern Apennines-Italy)

摘要

The Northern Apennines (NA) were predominantly formed by a Meso-Cenozoic sedimentarysequence thrust northeast and stacked over the Adriatic foreland during LateMiocene-Pleistocene. Extension on the Tyrrhenian margin is synchronous with thrustemplacements along the external Apenninic chain and is associated by crustal thinning,normal faulting, ductile deformation, volcanic activity and high heat flow. Both,the extensional and the compressional fronts migrated towards the Adriatic forelandduring the Plio-Pleistocene. Crustal extension everywere disrupted structural architecturesformed during the preceding compressional phase leading to the development ofthinned, uplifted and extended crust in the Tuscany mainland. Several models havebeen proposed to explain the evolution of the NA that are acknowledged to be tectonicallycomplex.We present results from a Receiver Functions (RFs) analysis of teleseismic eventsrecorded at Arezzo seismic station (Tuscany). A broad-band station (ARZ) is installedon the north-east margin of the “Val di Chiana” extensional syntectonic basin. Weselected and grouped in “bins” high signal/noise teleseismic events of four years ofrecording to compute a data-set of RFs. We applied a classical inversion scheme (aNeighbourhood Algorithm) and we carried out a three-dimensional modelling. As acriterion to identify and to distinguish the effects of azimuthal anisotropy from those oflateral heterogeneity, we included the harmonic angular analysis performed by stackingRadial (R) and Transverse (T) components with weights depending on the backazimuth.The results of these analysis provide a detailed three-dimensional image ofthe S-velocity lithosphere structure.