On focal points of SKS

Abstract

Although SKS is one of the most important phases in investigating the core of the earth, apparently it has not yet been noted that it may have one or more focal points. The full lines in figure 1 show the observed parts of the travel-time curves (epicentral distance θ, time t) of S, ScS, and SKS in the region between 73 and 88 degrees. The problem is to find the first part of the SKS curve at distances preceding the intersection of the travel-time curves of S and SKS.

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