Investigating seismic anisotropy beneath the Reykjanes Ridge using models of mantle flow, crystallographic evolution, and surface wave propagation
Investigating seismic anisotropy beneath the Reykjanes Ridge using models of mantle flow, crystallographic evolution, and surface wave propagation
Date
2013-08
Authors
Gallego, A.
Ito, Garrett
Dunn, R.A.
Contributor
Advisor
Department
Instructor
Depositor
Speaker
Researcher
Consultant
Interviewer
Annotator
Journal Title
Journal ISSN
Volume Title
Publisher
American Geophysical Union
Volume
Number/Issue
Starting Page
Ending Page
Alternative Title
Abstract
Surface wave studies of the Reykjanes Ridge (RR) and the Iceland hotspot have imaged an unusual and enigmatic pattern of two zones of negative radial anisotropy on each side of the RR. We test previously posed and new hypotheses for the origin of this anisotropy, by considering lattice preferred orientation (LPO) of olivine A-type fabric in simple models with 1-D, layered structures, as well as in 2-D and 3-D geodynamic models with mantle flow and LPO evolution. Synthetic phase velocities of Love and Rayleigh waves traveling parallel to the ridge axis are produced and then inverted to mimic the previous seismic studies. Results of 1-D models show that strong negative radial anisotropy can be produced when olivine a axes are preferentially aligned not only vertically but also subhorizontally in the plane of wave propagation. Geodynamic models show that negative anisotropy on the sides of the RR can occur when plate spreading impels a corner flow, and in turn a subvertical alignment of olivine a axes, on the sides of the ridge axis. Mantle dehydration must be invoked to form a viscous upper layer that minimizes the disturbance of the corner flow by the Iceland mantle plume. While the results are promising, important discrepancies still exist between the observed seismic structure and the predictions of this model, as well as models of a variety of types of mantle flow associated with plume-ridge interaction. Thus, other factors that influence seismic anisotropy, but not considered in this study, such as power-law rheology, water, melt, or time-dependent mantle flow, are probably important beneath the Reykjanes Ridge.
Description
Keywords
Reykjanes Ridge,
Iceland hotspot,
Anisotropy,
surface waves,
seismic inversion,
mantle flow
Citation
Gallego, A., G. Ito, and R. A. Dunn (2013), Investigating seismic anisotropy beneath the Reykjanes Ridge using models of mantle flow, crystallographic evolution, and surface wave propagation, Geochem. Geophys. Geosyst., 14, 3250–3267, doi:10.1002/ggge.20204.
Extent
18 pages
Format
Geographic Location
Time Period
Related To
Table of Contents
Rights
© 2013. American Geophysical Union. All Rights Reserved.
Rights Holder
Local Contexts
Collections
Email libraryada-l@lists.hawaii.edu if you need this content in ADA-compliant format.