29 June 2012 – Seminar

When: 4pm on Friday, 29th June 2012
Where: DIAS, Geophysics Section, 5 Merrion Square, Dublin 2, (library)

Speaker: Meghan S. Miller (University of Southern California)
Title: Segmented slabs beneath the central Mediterranean

Abstract:

To advance our understanding of the complex and episodic tectonic history of the central Mediterranean, we image the characteristics and structure of the convergent African and Eurasian lithospheric plates using S receiver functions. Specifically we investigate the lithospheric structure in terms of seismic velocity discontinuities, including the crust-mantle boundary (Moho) and the lithosphere-asthenosphere boundary (LAB) beneath Italy.  The geometry and continuity of these structures are explored using teleseismic S-to-P converted phases, applied extensively throughout this region for the first time. Beneath the Northern Apennines and Calabria, where subduction is still active, we find evidence for a complex lithospheric structure, where two different negative S-velocity jumps are present at approximately 90 and 180 km depth. The shallowest negative phases are interpreted as the base of the lithosphere, but the second negative phases are much deeper than expected for the overriding plate lithosphere.  When compared to hypocenter locations and p-wave tomography these deep converted phases correlate with the base of fast velocities perturbations in the upper mantle and regions with subcrustal earthquakes. These observations suggest that these deepest negative phases correspond to the base of the actively subducting lithosphere beneath the Northern Apennines and Calabria, and where these phases are absent in the receiver functions there is no subducting slab.  Seismic imaging of the lithosphere and uppermost mantle using S-to-p conversions provides another geophysical dataset to aid in interpretation of the complex, segmented slab structure beneath Italy.