Abstract
Fundamental mode Rayleigh wave phase and group velocities between 15 and 50 seconds are measured along different paths in the northeastern United States (NEUS). Interstation paths are selected that lie mainly in the Precambrian Grenville province or the Appalachian orogenic belt. Although the differences between the two paths are not significant under consideration of measurement errors, separate inversions yield velocity models that are consistent with previous travel-time studies. The Appalachians appear to have a slightly thicker crust with higher velocities in the lower crust relative to the Grenville province. Also, the phase and group velocities in the NEUS appear to lie between those of the Canadian Shield and the central United States. Phase and group velocities between 15 and 40 seconds are also measured across the M.I.T. short-period seismic network in southeastern New England for two large events using frequency-wavenumber analysis. Beamforming indicates that the sporter period Rayleigh waves (T∼15 sec) can arrive as much as 15 degrees off-azimuth. The Rayleigh wave phase and group velocities in this region suggest relatively high shear velocities in the mid to lower crust.
Published Version
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