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Asthenospheric channeling of the Icelandic upwelling: Evidence from seismic anisotropy

Summary: Asthenospheric channeling of the Icelandic upwelling:
Evidence from seismic anisotropy
Mei Xue*,1
, Richard M. Allen1
Department of Geology and Geophysics, University of Wisconsin-Madison, 1215 West Dayton Street, Madison, WI 53706, USA
Received 15 June 2004; received in revised form 17 March 2005; accepted 20 March 2005
Available online 19 May 2005
Editor: R.D. van der Hilst
Two end-member geometries, radial flow and ridge-channeled flow, have been proposed for the dispersion of material
upwelling beneath Iceland. Seismic anisotropy provides information on mantle flow, and therefore has the potential to
discriminate these two geometries. In this study, we combine the HOTSPOT and SIL datasets (39 stations) and select 28 events
for teleseismic shear-wave splitting analysis. Splitting results in central and eastern Iceland show 1­2 s splitting times with an
average NNW­SSE orientation of the fast splitting direction and an anti-clockwise rotation of fast axes from east to central
Iceland. In western Iceland, smaller splits with more N­S orientations are observed. Since crustal splitting times in Iceland are 0.1
s to 0.3 s, our delays of up to 2 s indicate a mantle source. Both the lack of dependence of the splitting parameters on event back
azimuth and the observations of null splits for events where the back azimuth is parallel or perpendicular to the fast splitting
directions (observed using other events) suggest that one layer of anisotropy dominates beneath Iceland. While both high stress
plus enriched water content and melt-rich layers can result in a 908 rotation of the fast splitting direction with respect to the flow
direction, we interpret our fast axis orientation as pointing in the direction of flow as the magnitude of stress is low and the


Source: Allen, Richard M. - Seismological Laboratory, Department of Earth and Planetary Science, University of California at Berkeley


Collections: Geosciences