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Published 1964 | Published
Book Section - Chapter Open

Recent evidence concerning the structure of the upper mantle from the dispersion of long period surface waves


Most of our present detailed knowledge concerning the earth's deep interior has come to us from the study of body-wave travel-time data, supplemented by the semi-empirical use of amplitude information. The use of travel-time information alone, even in areas where it can be applied, has severe limitations. Velocity reversals lead to fundamental theoretical difficulties, and discontinuities in velocity or velocity gradient lead to formidable practical difficulties. However, it is just these features of the earth that are most interesting and important in discussions of earth history, mantle composition, phase changes, and convection. The long debate over the low-velocity zone and the so-called 20° discontinuity illustrates the nature of the difficulties.

Additional Information

© 1964 University of Michigan. This research was partially supported by the Air Force Office of Scientific Research, Contract AF-AFOSR-25-63, as part of the Advanced Research Projects Agency, Project VELA.

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August 19, 2023
January 13, 2024