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Attenuation of body waves and the Q structure of the mantle

1968; American Geophysical Union; Volume: 73; Issue: 6 Linguagem: Inglês

10.1029/jb073i006p02195

2156-2202

Ta‐Liang Teng,

Geophysics and Sensor Technology

Journal of Geophysical Research (1896-1977)Volume 73, Issue 6 p. 2195-2208 Attenuation of body waves and the Q structure of the mantle Ta-Liang Teng, Ta-Liang TengSearch for more papers by this author Ta-Liang Teng, Ta-Liang TengSearch for more papers by this author First published: 15 March 1968 https://doi.org/10.1029/JB073i006p02195Citations: 108AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract The variation of Qα with depth is studied using the spectrums of a large number of P waves from two deep earthquakes. Two assumptions are made: (1) the normalized source spectrum is not a function of the angle of radiation; (2) Qα is independent of frequency, at least within the band of ƒ = 0.01 to 0.2 cps. Spectral ratios of two body waves are used to eliminate the source effect and the effect of the wave front divergence. It is shown that, when instrumental and crustal effects are removed, the logarithm of the spectral ratio is a linear function of frequency. The coefficient of the linear term, called the differential attenuation, is used to invert for a Qα depth structure. Two possible Qα models are presented, both of which have a low-Q upper mantle about 950 km deep with an average Qα of about 93. This is followed by a high-Q middle and lower mantle where Qα varies from 250 to 1000. Both models suggest a low-Q layer about 200 km thick near the bottom of the mantle with an average Qα of about 150. The Qα models represent preliminary attempts to deduce the Qα structure of the earth and should be regarded as tentative, particularly the portion of the model near the bottom of the mantle. Results of the present study are comparable with the Q values obtained by other authors. Major sources of errors are discussed in light of further refinement of the experiment. References Anderson, D. L., C. B. Archambeau, The anelasticity of the earth, J. Geophys. Res., 69, 2071, 1964. Anderson, D. L., A. Ben-Menahem, C. B. Archambeau, Attenuation of seismic energy in the upper mantle, J. Geophys. Res., 70, 1441, 1965. Anderson, D. L., R. L. Kovach, Attenuation in the mantle and rigidity of the core from multiply reflected core phases, Proc. Natl. Acad. Sci. U. S., 51, 168, 1964. Asada, T., K. Takano, Attenuation of short period P waves in the mantle, J. Phys. Earth, 11, 25, 1963. Attewell, P. B., Y. V. 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