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End of subduction in northern Apennines confirmed by observations of quasi-Love waves from the great 2004 Sumatra-Andaman earthquake
Department of Geological Sciences, Rutgers University, Piscataway, New Jersey, USA
Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy
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.
Citation: (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.
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