Taking advantage of the French nuclear test site in Southcentral Pacific for the analysis of PKP seismic waves, a systematic study around amplitude and arrival times was undertaken. A peak in the amplitude versus distance curves at 145¿5 was observed with amplitudes up to 20 times larger than observed amplitudes in the 130-140¿ distance range. This peak, together with six secondary maxima in the 142-147¿ distance range is in good agreement with theoretical amplitude versus distance curves computed from interference phenomena and Airy diffraction theory. Some variation of blast site epicenter and energy provides the best check of the amplitude oscillations versus frequency and distance.