Inversion of seismic waveforms for shear wave velocity structure in the lowermost mantle beneath the Hawaiian hotspot

We perform waveform inversion for the radial profile of shear wave velocity in the lowermost mantle beneath the Hawaiian hotspot. The data used in this study are waveforms observed mainly at epicentral distances around 90 degrees. The dataset includes waveforms from the CANOE (CAnadian NOrthwest Experiment) array and from the CNSN (Canadian National Seismographic Network). These data greatly enhance the resolution of the lowermost mantle as compared to earlier studies. We find a velocity decrease in the depth range from 2700 km to the core-mantle boundary (CMB), which is interpreted as probably due to a temperature increase. The results of the present paper, taken together with our previous results for other regions beneath the Pacific, suggest that there is a large amount of impurities such as aluminum and iron beneath Hawaii and that there is strong lateral heterogeneity in D '' beneath the Pacific. (C) 2010 Elsevier B.V. All rights reserved.