Constraints on a plume in the mid-mantle beneath the Iceland region from seismic array data

Teleseismic P waves passing through low-wave-speed bodies in the mantle are refracted, causing anomalies in their propagation directions that can be m easured by seismometer arrays. Waves from earthquakes in the eastern Pacifi c and western North America arriving at the NORSAR array in Norway and at s eismic stations in Scotland pass beneath the Iceland region at depths of si milar to 1000-2000 km. Waves arriving at NORSAR have anomalous arrival azim uths consistent with a low-wave-speed body at a depth of similar to 1500 km beneath the Iceland-Faeroe ridge with a maximum diameter of similar to 250 km and a maximum wave-speed contrast of similar to 1.5 per cent. This agre es well with whole-mantle tomography results, which image a low-wave-speed body at this location with a diameter of similar to 500 km and a wave-speed anomaly of similar to 0.5 per cent, bearing in mind that whole-mantle tomo graphy, because of its limited resolution, broadens and weakens small anoma lies. The observations cannot resolve the location of the body, and the ano maly could be caused in whole or in part by larger bodies farther away, for example by a body imaged beneath Greenland by whole-mantle tomography.