P waves traveling from events in the Tonga-Kermadec seismic zone to stations in New Zealand are very fast with highly emergent, dispersed waveforms. In this study 1191 broad-band and 2076 short period seismograms from 71 events are analysed for polarization of the initial P wave. The polarization directions are found to be up to 30° off the great circle path and consistently steep (20° from vertical). The polarization directions for a tilted interface beneath the array are inverted and arrival times are used to control the depth to the interface, which is found to lie close to the top of the subducted plate inferred from the seismicity. These precursive, emergent P waves appear to have traveled through a fast layer close to the top of the subducted plate and refract upward to the station.