Skip to Main content Skip to Navigation
New interface
Journal articles

Upper-mantle flow beneath French Polynesia from shear wave splitting

Abstract : Upper-mantle flow beneath the South Pacific is investigated by analysing shear wave splitting parameters at eight permanent long-period and broad-band seismic stations and 10 broad-band stations deployed in French Polynesia from 2001 to 2005 in the framework of the Polynesian Lithosphere and Upper Mantle Experiment (PLUME). Despite the small number of events and the rather poor backazimuthal coverage due to the geographical distribution of the natural seismicity, upper-mantle seismic anisotropy has been detected at all stations except at Tahiti where two permanent stations with 15 yr of data show an apparent isotropy. The median value of fast polarization azimuths (N67.5°W) is parallel to the present Pacific absolute plate motion direction in French Polynesia (APM: N67°W). This suggests that the observed SKS fast polarization directions result mainly from olivine crystal preferred orientations produced by deformation in the sublithospheric mantle due to viscous entrainment by the moving Pacific Plate and preserved in the lithosphere as the plate cools. However, analysis of individual measurements highlights variations of splitting parameters with event backazimuth that imply an actual upper-mantle structure more complex than a single anisotropic layer with horizontal fast axis. A forward approach shows that a two-layer structure of anisotropy beneath French Polynesia better explains the splitting observations than a single anisotropic layer. Second order variations in the measurements may also indicate the presence of small-scale lateral heterogeneities. The influence of plumes or fracture zones within the studied area does not appear to dominate the large-scale anisotropy pattern but may explain these second-order splitting variations across the network.
Document type :
Journal articles
Complete list of metadata

Cited literature [101 references]  Display  Hide  Download

https://hal.archives-ouvertes.fr/hal-01249275
Contributor : Fabrice Fontaine Connect in order to contact the contributor
Submitted on : Thursday, December 31, 2015 - 11:09:01 AM
Last modification on : Tuesday, September 6, 2022 - 5:01:32 PM
Long-term archiving on: : Tuesday, April 5, 2016 - 1:46:58 PM

File

GJI2007SKS.pdf
Publisher files allowed on an open archive

Identifiers

Collections

Citation

Fabrice R. R. Fontaine, Guilhem Barruol, Andrea Tommasi, Götz H.R. Bokelmann. Upper-mantle flow beneath French Polynesia from shear wave splitting. Geophysical Journal International, 2007, 170, ⟨10.1111/j.1365-246X.2007.03475.x⟩. ⟨hal-01249275⟩

Share

Metrics

Record views

248

Files downloads

103