HR: 16:15h
AN: S14A-02 INVITED    [Abstracts]
TI: A Seismically Sharp Lithospheric Base Persisting to the Lowermost Mantle Beneath the Caribbean
AU: * Kito, T
EM: tkito@liverpool.ac.uk
AF: Depertment of Earth and Ocean Sciences, University of Liverpool, Jane Herdman Laboratories 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Thomas, C
EM: tine@liverpool.ac.uk
AF: Depertment of Earth and Ocean Sciences, University of Liverpool, Jane Herdman Laboratories 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Rietbrock, A
EM: A.Rietbrock@liverpool.ac.uk
AF: Depertment of Earth and Ocean Sciences, University of Liverpool, Jane Herdman Laboratories 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Garnero, E J
EM: garnero@asu.edu
AF: School of Earth and Space Exploration, Arizona State University, Tempe AZ 85287-1404, Tempe, AZ 85287-1404, United States
AU: Nippress, S
EM: Nippress@liverpool.ac.uk
AF: Depertment of Earth and Ocean Sciences, University of Liverpool, Jane Herdman Laboratories 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AU: Heath, A
EM: aeh@liverpool.ac.uk
AF: Depertment of Earth and Ocean Sciences, University of Liverpool, Jane Herdman Laboratories 4 Brownlow Street, Liverpool, L69 3GP, United Kingdom
AB: The detailed structure of lower mantle slabs is not well known and it is crucial to examine the fate of subducted slabs in the mid- and lower mantle, since it is closely related to the question of mantle convection pattern and mass flux across the mantle transition zone. To address this problem, we applied a newly developed seismic wave migration method to broadband data recorded by Californian seismic networks from South American earthquakes. Out-of-plane seismic P wave reflections which propagate from the source are reflected at seismic heterogeneities and arrive at the stations, are observed beneath the Cocos plate. The reflection locations extend through Earthfs lower mantle down to the core-mantle boundary (CMB), and coincide with the edges of tomographically mapped high seismic velocities. The observed energy is well explained by underside reflections off a sharp contrast between the base of the former depleted harzburgitic Nazca plate lithosphere and the viscously entrained more fertile underlying lherzolitic former asthenosphere. We also detect weaker reflections corresponding to the apparent top of the slab, which may arise from the boundary between the Nazca plate and the overlying former basaltic oceanic crust. Mass flux across the 670 km discontinuity of the former oceanic asthenosphere, lithosphere and basaltic crust is thus supported, intimately linking processes and structure at the top and bottom of Earthfs mantle by large scale mantle flow.
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Seismology [S]
MN: 2007 Fall Meeting