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AGU: Geophysical Research Letters

 

Keywords

  • SKS splitting
  • seismic anistropy
  • French Polynesia

Index Terms

  • Seismology: Body waves
  • Seismology: Mantle
  • Tectonophysics: Dynamics of lithosphere and mantle: general
  • Tectonophysics: Dynamics: convection currents, and mantle plumes
  • Marine Geology and Geophysics: Oceanic hotspots and intraplate volcanism

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L14301, 5 PP., 2009
doi:10.1029/2009GL038139

Mapping upper mantle flow beneath French Polynesia from broadband ocean bottom seismic observations

G. Barruol

Géosciences Montpellier, Université Montpellier II, CNRS, Montpellier, France

D. Suetsugu

Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

H. Shiobara

Earthquake Research Institute, University of Tokyo, Tokyo, Japan

H. Sugioka

Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

S. Tanaka

Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

G. H. R. Bokelmann

Géosciences Montpellier, Université Montpellier II, CNRS, Montpellier, France

F. R. Fontaine

Laboratoire GéoSciences Réunion, Université de la Réunion, CNRS, Saint Denis, Reunion, France

D. Reymond

LDG, Commissariat à l'Energie Atomique, Papeete, French Polynesia

Upper mantle structures and flow related to the South Pacific Superswell and to the associated short-lived hotspots are investigated using seismic stations deployed in French Polynesia. Beside island stations, broadband ocean bottom seismometers (BBOBS) have been deployed between the various Polynesian archipelagos to investigate the oceanic upper mantle “unperturbed” by thickened crust or hotspot activity. We investigate seismic anisotropy measured at BBOBS stations and found it rather similar to that from island stations. This confirms the ability of OBS to be used for anisotropy purposes and suggests some homogeneity in the upper mantle pervasive deformation. The two OBS installed on the head of the Society hotspot provide different anisotropy signatures than most of the other French Polynesian stations: one is “isotropic” to SKS waves and the other provides a fast split direction normal to the average value observed in this area, suggesting a more complex mantle flow induced by the plume upwelling.

Received 18 March 2009; accepted 22 June 2009; published 21 July 2009.

Citation: Barruol, G., D. Suetsugu, H. Shiobara, H. Sugioka, S. Tanaka, G. H. R. Bokelmann, F. R. Fontaine, and D. Reymond (2009), Mapping upper mantle flow beneath French Polynesia from broadband ocean bottom seismic observations, Geophys. Res. Lett., 36, L14301, doi:10.1029/2009GL038139.

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