Mathematics
Scientific paper
May 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989mit..reptr....j&link_type=abstract
Final Technical Report, 9 Jun. 1987 - 8 Nov. 1988 Massachusetts Inst. of Tech., Cambridge. Dept. of Earth, Atmospheric, and Plan
Mathematics
Earth Core, Earth Mantle, Love Waves, Mathematical Models, Phase Velocity, Rayleigh Waves, Surface Waves, Anisotropy, Asia, Earth Planetary Structure, Europe, Isotropism, Pulse Amplitude, Reflection, S Waves, Seismology, Siberia, Structural Properties (Geology), U.S.S.R., Vertical Orientation, Waveforms
Scientific paper
A new set of waveform-analysis procedures to recover phase and amplitude information from seismograms was evaluated. These procedures appear to be capable of making fundamentally new observations about the structure of the earth's interior. They were used to measure travel times and quality factors of body waves, including those embedded in complex wavetrains, as well as dispersion and attenuation of surface waves, including higher modes. These techniques were applied to three component seismograms to investigate the structure of the Eurasian upper mantle, made observations of shear wave splitting on long period records of multiply reflected S waves bottoming in the upper mantle beneath the Russian and Siberian platforms. Dispersion of Love and Rayleigh waves over these paths shows discrepancies of comparable or larger magnitude with respect to smooth isotropic structures, consistent with a model of the uppermost mantle having significant apparent vertical anisotropy. Although the splitting and dispersion data can be fit by smooth anisotropic models, we investigated the apparent anisotropy associated with fine-scale (rough) structure beneath stable Eurasia. The data was fitted with a rough isotropic model having an rms shear velocity fluctuation that varies from 14 percent in the uppermost mantle to zero at 400-km depth. The fluctuations are larger than the variation expected for even a diverse assemblage of upper mantle ultrabasic rocks, which was taken as evidence for some sort of intrinsic (local) anisotropy.
Gee Lind S.
Jordan Thomas H.
Revenaugh Justin S.
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