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Published June 1960 | Published
Journal Article Open

PKIKP and Pseudo-PKIKP Phases at distances of less than 140°

Gutenberg, B.

Abstract

In several attempts to establish from observations the travel-time curve for PKIKP (called P′ or P″ by some authors) the beginning of this curve has been drawn with a relatively strong curvature corresponding to a decrease of dt/dθ from roughly 4 s/deg at θ = 110° to about 2 s/deg at 130°. Apparently, travel times of different wave types had been combined. Actually, the observed travel-time curve of PKIKP is nearly a straight line in agreement with calculations. Near an epicentral distance of 115° the amplitudes of PKIKP increase by a factor of roughly 5. This probably indicates the transition from the diffracted to the direct PKIKP. The portions of the travel-time curves with a slope corresponding to dt/dθ near 4 s/deg which erroneously had been attributed to PKIKP belong to several wave types which seem to follow P, pP and sP or precede PP, each at roughly constant time intervals. Among causes for such multiplicity of phases are effects of irregularities in the Earth, of discontinuities and of diffraction.

Additional Information

Copyright © 1960 The Royal Astronomical Society. (Received 1959 December 14). Contribution No. 959 from the Division of the Geological Sciences, California Institute of Technology.

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Created:
August 19, 2023
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