HR: 11:00h
AN: V21F-03    [PDF]
TI: The Upper Mantle Under the South Pacific Super-Swell from Multimode Surface Waveform Tomography
AU: * Maggi, A
EM: Alessia.Maggi@eost.u-strasbg.fr
AF: Ecole et Observatoire des Sciences de la Terre, CNRS, Universite Louis Pasteur,, Strasbourg, 67084 France
AU: Debayle, E
EM: Eric.Debayle@eost.u-strasbg.fr
AF: Ecole et Observatoire des Sciences de la Terre, CNRS, Universite Louis Pasteur,, Strasbourg, 67084 France
AU: Debayle, E
EM: Eric.Debayle@eost.u-strasbg.fr
AF: Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, CB3 0EZ United Kingdom
AU: Priestley, K
EM: keith@madingley.org
AF: Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, CB3 0EZ United Kingdom
AU: Barruol, G
EM: gjilhem.barruol@upf.pf
AF: Jeune Equipe Terre Ocean, CNRS, Universite de la Polynesie Francaise, Faaa, 98702 French Polynesia
AU: Fontaine, F
EM: Fabrice.Fontaine@dstu.univ-montp2.fr
AF: Laboratoire de Tectonophysique, Universite Montpellier II, CNRS, Montpellier, 34095 France
AU: Reymond, D
EM: cppt@labogeo.pf
AF: Laboratoire de Geophysique, CEA, Patami, Faaa, 98702 French Polynesia
AB: The South Pacific contains a swarm of volcanic island chains superimposed on a broad bathymetric high known as the South Pacific Superswell. The islands and swell are thought to be the surface manifestation of a ``superplume'' beneath the the region. We present a Sv-wave speed tomographic model for the South Pacific derived from multi-mode waveform inversion of more than 17,000 vertical component seismograms. Most of the data are from the Global Digital Seismic Network but we include important data from ten broadband seismographs deployed in French Polynesia as part of the PLUME experiment (Polynesia Lithosphere and Upper Mantle Experiment). We use preferentially short propagation paths ($\Delta < 54^{\circ}$) to minimize off great circle path propagation, but increase the path length in areas of insufficient coverage. We resolve the subduction zones bounding the South Pacific to the east and west with a width compatible with the smoothing used in the tomographic inversion. The slow wave speed structure associated with the East Pacific Rise is offset to the west as has previously been noted in more detailed local studies. There seems to be no pervasive low wave speed feature in the upper mantle beneath the South Pacific. However, low wave speed structures extend from shallow depth to the transition zone beneath the Society hotspot, the Austral hotspot and Easter Island. The presence of similar structures beneath other Pacific hotspots is currently masked by lack of resolution.
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting