Upper-mantle fabrics beneath the Northern Apennines revealed by seismic anisotropy

Authors

  • Helena Munzarová,

    Corresponding author
    1. Geophysical Institute, Academy of Sciences of the Czech Republic, Boční II/1401, Czech Republic
    2. Department of Geophysics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
    • Corresponding author: H. Munzarová, aGeophysical Institute, Academy of Sciences of the Czech Republic, Boční II/1401, 141 31 Prague 4, Czech Republic. (helena@ig.cas.cz)

    Search for more papers by this author
  • Jaroslava Plomerová,

    1. Geophysical Institute, Academy of Sciences of the Czech Republic, Boční II/1401, Czech Republic
    Search for more papers by this author
  • Vladislav Babuška,

    1. Geophysical Institute, Academy of Sciences of the Czech Republic, Boční II/1401, Czech Republic
    Search for more papers by this author
  • Luděk Vecsey

    1. Geophysical Institute, Academy of Sciences of the Czech Republic, Boční II/1401, Czech Republic
    Search for more papers by this author

Abstract

[1] We image anisotropic structure of the upper mantle beneath the Northern Apennines based on body-wave data collected during the RETREAT experiment (2003–2006). Joint analysis of anisotropic parameters evaluated from independent data sets—teleseismic P-wave travel times and shear-wave splitting—allows us to identify regions of different fabrics both in the mantle lithosphere and in the sublithospheric mantle. We recognize three regions—the Tyrrhenian, Adriatic, and Transition—with their own anisotropic characteristics. The slab-parallel flow prevails in the sublithospheric mantle beneath the thin Tyrrhenian plate, while nearly slab-perpendicular orientation of the high velocities dominates on the Adriatic side of the region. The asthenospheric-flow pattern excludes a simple corner-flow model to fit the fabric of the upper mantle in the syn-convergent extensional tectonics and suggests the end of the subduction roll-back. We map fossil anisotropy with inclined symmetry axes within two domains of the thick continental Adriatic lithosphere. We estimate the lithosphere thickness of the Tyrrhenian and Adriatic plates at ~50 km and ~80 km, respectively, the latter being subducted down to no more than ~200 km with indications of inherited frozen-in anisotropic fabric. If a potential detachment at the northern end of the Apennine slab exists, then it would have to be narrow and in its initial stage. Synthetic tests of the well-known trade-off between isotropic heterogeneity and evaluated anisotropic parameters, along with combining independent data sets, document a sufficient separation of both effects.

Ancillary