Seismic Waves Reflected from Discontinuities within Earth's Upper Mantle

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Science  10 Jan 1969:
Vol. 163, Issue 3863, pp. 177-179
DOI: 10.1126/science.163.3863.177


Precursors to normtial seismic waves of the PKPPKP type in the distance range of 55° to 75° are ascribed to reflection of this phase from within the earth's upper mantle. The new observations confirm the existence of a sharply defined transition zone, probably worldwide in extent, at a depth of approximately 650 kilometers. These data are shown to be a useful tool for the study of upper mantle structure on a global basis.

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