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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L07308, doi:10.1029/2007GL029302, 2007

Abrupt change in mantle fabric across northern Apennines detected using seismic anisotropy

S. Salimbeni

Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy
Centro Nazionale Terremoti, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy


S. Pondrelli

Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy


L. Margheriti

Centro Nazionale Terremoti, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy


V. Levin

Department of Geological Sciences, Rutgers University, Piscataway, New Jersey, USA


J. Park

Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA


J. Plomerova

Geophysical Institute, Czech Academy of Science, Prague, Czech Republic


V. Babuska

Geophysical Institute, Czech Academy of Science, Prague, Czech Republic


Abstract

We estimated SKS splitting parameters for 18 earthquakes observed over 2 years on a dense linear seismometer array crossing the Apennines orogen (Northern Italy). An abrupt (within 30 km) change in fast polarization occurs near the crest of the Apennines. Southwest of the crest, fast polarization parallels the Apennines strike (WNW–ESE), rotating to EW orientation near the Tyrrhenian Sea. Northeast of the crest, toward the Po Plain, fast polarization is NNE–SSW, roughly normal to the orogen's strike. Delay times (0.6–2.9s) do not show a remarkable pattern. Splitting parameters beneath the Apennines argue against anisotropy restricted to the crust, and suggest that the mantle region deformed by Apennines slab rollback is spatially limited. We hypothesize that the rollback process has been uneven, evolving to a contortion of the northern edge of the Apennines slab, and perhaps incipient detachment. Lithospheric anisotropy beneath the Po-Plain may also be significant.

Received 16 January 2007; accepted 9 March 2007; published 14 April 2007.

Keywords: anisotropy; mantle deformation; geodynamics.

Index Terms: 7208 Seismology: Mantle (1212, 1213, 8124); 7240 Seismology: Subduction zones (1207, 1219, 1240); 8011 Structural Geology: Kinematics of crustal and mantle deformation.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 484528 bytes)

Citation: Salimbeni, S., S. Pondrelli, L. Margheriti, V. Levin, J. Park, J. Plomerova, and V. Babuska (2007), Abrupt change in mantle fabric across northern Apennines detected using seismic anisotropy, Geophys. Res. Lett., 34, L07308, doi:10.1029/2007GL029302.