Regional travel times of P and S seismic waves between Fiji and New Zealand

Three years' observations of Tonga‐Fiji‐Kermadec earthquakes at stations in New Zealand have been analysed by the statistical techniques applied to Herrin's “1968 Seismological Tables for P Phases”, to yield smoothed regional travel times for P and S . The travel‐time curve for P is later than Herrin's until it merges with it at about 30°, implying lower velocities than those of Herrin's model at shallow levels in the upper mantle, and higher velocities at deeper levels. The travel‐time curve for S crosses the Jeffreys‐Bullen curve at 21° and 27° and has a greater curvature in this range. A correlation between the isostatic gravity anomaly and the mean travel‐time residual at the stations is tentatively explained in terms of higher velocities in the deep seismic zone.