Travel Times of PKP in the Range 115� ? ? ? 140�

Approximately 500 observations of PKP in the range 115 °⩽Ɗ⩽ 140 ° have been statistically examined to yield a set of empirical travel times. Observations for the DE branch (PKIKP) fit the form t= 9092·5 s + 1·876Δ later by 1·8 to 1·0 s than the corresponding times given by Jeffreys & Bullen. The mean residual of all observations of PKIKP from nuclear explosions, including recent data from Longshot, against the empirical times does not significantly differ from zero emphasizing that average PKIKP times for a reference Earth are now satisfactorily known. In the interval 125 ° < Δ < 140° observations preceding the DE branch satisfy the relation t= 1145·0 + 2·2(Δ−132·5°) with a large standard error; these observations probably correspond to one or more precursor branches to the DE branch.