Surface wave tomography of the upper mantle beneath the Reykjanes Ridge

Abstract

This study analyzed broadband records for fundamental mode Love and Rayleigh waves that propagated along the Reykjanes Ridge to study the seismic properties in the upper mantle as it relates to hotspot-ridge interaction. These waves were generated by regional earthquakes occurring in the North Atlantic to the south of Iceland, and were recorded by the HOTSPOT and ICEMELT arrays and the GSN station BORG, located on Iceland. The phase, group, and amplitude information were measured for narrow-pass filtered waveforms over the period range of -12-100s. Over -12,000 such measurements were included in an inversion for mantle and lithospheric shear velocity structure: in addition the joint inversion of horizontally polarized Love and vertically polarized Rayleigh wave data solved for mantle seismic anisotropy. Shear wave velocity results show a broad and deep low velocity zone in the upper mantle which is consistent with elevated temperatures and a small degree of partial melt. Shear wave anisotropy results indicate that vertically polarized shear waves are faster than horizontally polarized shear waves in the uppermost mantle within -200 km of the ridge. This study shows that plume material that spreads out beneath the Reykjanes Ridge from Iceland is not confined to a lithospheric channel beneath the ridge.