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Published August 1982 | Published
Journal Article Open

Worldwide distribution of group velocity of mantle Rayleigh waves as determined by spherical harmonic inversion


We have determined the worldwide distribution of group velocity of mantle Rayleigh waves for periods between 100 and 300 sec without assuming any regionalization. Group slowness 1/u(θ, φ) is expressed by spherical harmonics, and the coefficients, up to angular order 7, have been determined from travel times of Rayleigh waves by a least-squares method. From these, u(θ, φ) has been synthesized. Since we cannot obtain information about the odd terms of the expansion from one circuit measurements around the world, we have used group velocities of mainly R_2 and R_3. The overall pattern of u(θ, φ) for periods between 100 and 200 sec is consistent with results of previous pure-path and regional studies. Group velocities for tectonically active regions are low, and those of the shields and the northwestern Pacific are high.

Additional Information

© 1982 Seismological Society of America. Manuscript received 23 December 1981. We thank Hiroo Kanamori for allowing us to use his magnetic tape that contains the seismograms used in this study and providing us valuable information on the seismograms and the earthquakes. We thank Jeff Given for calculating a synthetic seismogram, which we used to check a computer program and allowing us to use his program that calculates the instrumental response of IDA stations. They kindly made available to us a preprint of their paper on the moment tensor inversion of the earthquakes that are used in this study. We wish to thank Fumiko Tajima for her assistance at all stages of this study. We also thank Ronan Le Bras and Larry Ruff for suggestions. The IDA data used in this study were made available to us by courtesy of the IDA project team at the Institute of Geophysics and Planetary Physics, University of California, San Diego. This research was supported by National Aeronautics and Space Administration (NSG-7610).

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August 19, 2023
October 26, 2023