Surface wave tomography of the upper mantle beneath the Reykjanes Ridge with implications for ridge-hot spot interaction

Publication Type  Journal Article
Year of Publication  2007
Authors  Delorey, A. A.; Dunn, R. A.; Gaherty, J. B.
Journal Title  Journal of Geophysical Research-Solid Earth
Volume  112
Issue  B8
Pages  -
Journal Date  Aug 24
ISBN Number  0148-0227
Accession Number  ISI:000249034300001
Key Words  east pacific rise; v-shaped ridges; seismic anisotropy; iceland plume; melt generation; midocean ridges; north-atlantic; flow beneath; dynamics; ocean

We modeled fundamental mode Love and Rayleigh waves to study the seismic properties of the upper mantle beneath the Reykjanes Ridge. These waves were generated by regional earthquakes occurring in the North Atlantic to the south of Iceland and were recorded by stations located on Iceland. Over 12,000 measurements of the phase, group arrival time, and amplitude of narrow-pass-filtered waveforms ( over the period range of 9.5-100 s) were used to solve for mantle shear wave velocity structure and anisotropy. In a vertical plane oriented normal to the ridge axis, the velocity structure contains a broad and deep low-velocity zone in the upper mantle beneath the ridge. A joint analysis of the seismic structure with gravity data reveals that the low velocities are consistent with elevated temperatures ( similar to 75 degrees). Our study shows that plume material spreads broadly outward beneath the Reykjanes Ridge from Iceland and is not confined to a narrow lithospheric channel. At distances > 200 km from the ridge, shear wave anisotropy indicates a predominant horizontal alignment of the fast axes of anisotropic crystals ( mainly above 50 km depth), which can be interpreted as past, horizontal, ridge-perpendicular flow. Within +/-200 km of the ridge the anisotropy indicates a general vertical alignment of the fast axes or an alignment such that the fast axes point along the ridge. The transition to this type of anisotropy coincides with the appearance of increased hot spot-ridge interaction similar to 20 Myr ago, indicating that plume flow has largely disrupted mantle flow beneath the ridge since that time.


204HJTimes Cited:0Cited References Count:91

URL  <Go to ISI>://000249034300001
DOI  Doi 10.1029/2006jb004785