@article {eddy_age_2019,
	title = {Age dependence and anisotropy of surface-wave phase velocities in the Pacific},
	journal = {Geophysical Journal International},
	volume = {216},
	number = {1},
	year = {2019},
	month = {01/2019},
	pages = {640{\textendash}658},
	abstract = {We present new anisotropic phase-velocity maps of the Pacific basin for Rayleigh and Love waves between 25~and 250~s. The isotropic and anisotropic phase-velocity maps are obtained by inversion of a data set of single-station surface-wave phase-anomaly measurements recorded for paths crossing the Pacific basin. We develop an age-dependent gradient-damping scheme that allows us to reduce the amount of smoothness damping required in the inversion. The observed isotropic phase velocities have a strong age dependence, and our results are consistent with models of half-space cooling: simple phase-velocity models that depend only on seafloor age explain \$40\textbackslashtext{-}97\textbackslashhbox{ per cent}\$ of the data variance for Love waves and \$20\textbackslashtext{-}97\textbackslashhbox{ per cent}\$ for Rayleigh waves. These values represent a large fraction, ranging from 0.55 to 0.99, of the variance reduction of our best-fitting phase-velocity models. We find that 2ζ azimuthal anisotropy is required to fit our Rayleigh wave phase-anomaly data set but that our data do not require Love wave anisotropy. Rayleigh wave anisotropy also exhibits a clear age dependence, with a large decrease in the magnitude of 2ζ azimuthal anisotropy for seafloor older than 70~Ma that cannot be explained simply as a change in anisotropy direction between the lithosphere and asthenosphere. Long-period Rayleigh wave anisotropy directions align well overall with absolute-plate-motion directions, with a median angular misfit of 20{\textdegree} at 125~s. However, we observe large areas within the Pacific basin with a small but consistent offset of 10{\textdegree}{\textendash}20{\textdegree} between the two directions. The disagreement between absolute plate motion and anisotropy for long-period waves suggests the presence of mantle flow beneath the base of the plate in a direction other than absolute plate motion.},
	issn = {0956-540X},
	doi = {10.1093/gji/ggy438},
	url = {https://doi.org/10.1093/gji/ggy438},
	author = {Eddy, Celia L and Ekstr{\"o}m, G{\"o}ran and Nettles, Meredith and Gaherty, James B}
}
