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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L04304, doi:10.1029/2006GL028860, 2007

End of subduction in northern Apennines confirmed by observations of quasi-Love waves from the great 2004 Sumatra-Andaman earthquake

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


F. P. Lucente

Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy


L. Margheriti

Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy


S. Pondrelli

Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy


Abstract

Surface waves from the great Sumatra-Andaman earthquakes of 2004 and 2005 that cross Italy south of ∼44°N display Love-to-Rayleigh scattered waves (quasi-Love phases) diagnostic of sharp lateral gradients in the anisotropic properties of Earth's upper mantle. Surface waves that traverse Italy further north lack this distinctive phase, documenting a change in the upper mantle fabric that is corroborated by a shift in the fast polarization of shear wave birefringence. These observations suggest that orogen-parallel asthenospheric extension behind the retreating Apennines slab has limited geographical expression. We hypothesize that subduction rollback currently terminates at 44°N, while the upper mantle flow pattern further to the north has been recently rearranged.

Received 29 November 2006; accepted 10 January 2007; published 21 February 2007.

Keywords: seismic anisotropy; rollback; northern Apennines.

Index Terms: 7255 Seismology: Surface waves and free oscillations; 8120 Tectonophysics: Dynamics of lithosphere and mantle: general (1213); 8170 Tectonophysics: Subduction zone processes (1031, 3060, 3613, 8413).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 340387 bytes)

Citation: Levin, V., J. Park, F. P. Lucente, L. Margheriti, and S. Pondrelli (2007), End of subduction in northern Apennines confirmed by observations of quasi-Love waves from the great 2004 Sumatra-Andaman earthquake, Geophys. Res. Lett., 34, L04304, doi:10.1029/2006GL028860.