Abstract
We present the results of a study of surface wave dispersion across
the Arctic region (>60N) and compare the estimating group velocity
maps with new maps of the body wave phases Pn and Sn. Data recorded
at about 250 broadband digital stations from several global and regional
networks were used to obtain Rayleigh and Love wave group velocity
measurements following more than 1100 events with magnitudes Ms>5.0
that occurred in the northern hemisphere from 1977 to 1998. These
measurements were used to construct both isotropic and 2Psi azimuthally
anisotropic group velocity maps from 15 to 200 s period. As elsewhere
in the world, the observed maps display the signatures of sedimentary
and oceanic basins, crustal thickness variations, and upper mantle
anomalies under both continents and oceans. We also present Pn and
Sn maps produced from a groomed data set of travel times from the
ISC and NEIC bulletins. The long period group velocity maps correlate
well with Pn and Sn velocities. Finally, at long wavelengths, the
estimated 2Psi azimuthal anisotropy in Rayleigh wave group velocity
correlates well with the azimuthal anisotropy in phase velocity obtained
in a global scale study of Trampert and Woodhouse. Because attempts
to improve the resolution to regional scales change both the amplitude
and the pattern of the inferred azimuthal anisotropy, caution should
be exercised in interpreting the anisotropy maps.
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