Opin vísindi

Shear wave splitting across the Iceland hot spot: Results from the ICEMELT experiment

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dc.contributor Háskóli Íslands
dc.contributor University of Iceland
dc.contributor.author Bjarnason, Ingi Þorleifur
dc.contributor.author Silver, Paul G.
dc.contributor.author Rümpker, Georg
dc.contributor.author Solomon, Sean C.
dc.date.accessioned 2018-02-26T11:12:30Z
dc.date.available 2018-02-26T11:12:30Z
dc.date.issued 2002-12
dc.identifier.citation Bjarnason, I. T., Silver, P. G., Rümpker, G., & Solomon, S. C. (2002). Shear wave splitting across the Iceland hot spot: Results from the ICEMELT experiment. Journal of Geophysical Research: Solid Earth, 107(B12), ESE 23-21-ESE 23-12. doi:10.1029/2001JB000916
dc.identifier.issn 0148-0227
dc.identifier.issn 2169-9356 (eISSN)
dc.identifier.uri https://hdl.handle.net/20.500.11815/575
dc.description.abstract We report on observations of upper mantle anisotropy from the splitting of teleseismic shear waves (SKS, SKKS, and PKS) recorded by the ICEMELT broadband seismometer network in Iceland. In a ridge-centered hot spot locale, mantle anisotropy may be generated by flow-induced lattice-preferred orientation of olivine grains or the anisotropic distribution of magma. Splitting measurements of teleseismic shear waves may thus provide diagnostic information on upper mantle flow and/or the distribution of retained melt associated with the Iceland mantle plume. In eastern Iceland, fast polarization directions lie between N10°W and N45°W and average N24°W; delay times between the fast and slow shear waves are generally 0.7–1.35 s. In western Iceland, in contrast, the fast polarization directions, while less well constrained, yield an average value of N23°E and delay times are smaller (0.2–0.95 s). We propose that splitting in eastern Iceland is caused by a 100- to 200-km-thick anisotropic layer in the upper mantle. The observed fast directions in eastern Iceland, however, do not correspond either to the plate spreading direction or to a pattern of radial mantle flow from the center of the Iceland hot spot. We suggest that the relatively uniform direction and magnitude of splitting in eastern Iceland, situated on the Eurasian plate, may therefore reflect the large-scale flow field of the North Atlantic upper mantle. We hypothesize that the different pattern of anisotropy beneath western Iceland, part of the North American plate, is due to the different absolute motions of the two plates. By this view, splitting in eastern and western Iceland is the consequence of shear by North American and Eurasian plate motion relative to the background mantle flow. From absolute plate motion models, in which the Eurasian plate is approximately stationary and the North American plate is moving approximately westward, the splitting observations in both eastern and western Iceland can be satisfied by a background upper mantle flow in the direction N34°W and a velocity of 3 cm/yr in a hot spot reference frame. This inference can be used to test mantle flow models. In particular, it is inconsistent with kinematic flow models, which predict southward flow, or models where flow is dominated by subduction-related sources of mantle buoyancy, which predict westward flow. Our observations are more compatible with the flow field predicted from global seismic tomography models, which in particular include the influence of the large-scale lower mantle upwelling beneath southern Africa. While the hypothesized association between our observations and this upwelling is presently speculative, it makes a very specific and testable prediction about the flow field and hence anisotropy beneath the rest of the Atlantic basin.
dc.description.sponsorship This work was supported by the National Science Foundation under grants EAR-9316137, OCE-9402991, and EAR-9707193.
dc.format.extent ESE 23-1-ESE 23-12
dc.language.iso en
dc.publisher Wiley-Blackwell
dc.relation.ispartofseries Journal of Geophysical Research: Solid Earth;107(B12)
dc.rights info:eu-repo/semantics/openAccess
dc.subject Anisotropy
dc.subject Hot spot
dc.subject Plate motion
dc.subject Shear wave splitting
dc.subject Mantle flow
dc.subject Jarðeðlisfræði
dc.subject Jarðmöttull
dc.subject Jarðskjálftar
dc.subject Landrek
dc.subject Bylgjufræði
dc.title Shear wave splitting across the Iceland hot spot: Results from the ICEMELT experiment
dc.type info:eu-repo/semantics/article
dcterms.license Copyright 2002 by the American Geophysical Union
dc.description.version Peer Reviewed
dc.identifier.journal Journal of Geophysical Research: Solid Earth
dc.identifier.doi 10.1029/2001JB000916
dc.relation.url https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2001JB000916
dc.contributor.department Raunvísindastofnun (HÍ)
dc.contributor.department Science Institute (UI)
dc.contributor.school Verkfræði- og náttúruvísindasvið (HÍ)
dc.contributor.school School of Engineering and Natural Sciences (UI)

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