Lateral diffraction of underwater sounds between Japan and Chile: experimental results and modeling

One hundred shallow underwater explosions on a 300-km profile along an isoline of 500 m sea depth above a slope zone of off the coast of Japan are received at a water-column hydrophone triplet with 2-km intervals in Chile. The over 16,000-km propagations from the northwest to the southeast Pacific Ocean are classified into two groups. One is from the southern explosions. The data show high sound pressure levels and normal travel times. On the other hand, data from the northern ones reveal 6.5 dB lower sound pressure levels and 6.6 s travel time delays on average. Some islands and seamounts in the central Pacific are located on the halfway from the northern explosions. They affect received sound pressure levels and arrival times, but do not block completely, based on the observation. Modeling of this propagation path, using in-plane 2D modeling, shows nearly complete blockage of the sound by the Northern Hawaiian Island chain. Three dimensional parabolic equation modeling shows that this shadow is filled i...