THE UNDERWATER ACOUSTIC SIGNATURE OF A NUCLEAR EXPLOSION AT THE OCEAN SURFACE

Abstract : The gross spectral character and duration of the acoustic wave signature of a nuclear explosion near the ocean surface is estimated by constructing theoretical pressure-time histories, using models for the explosion and wave propagation. The explosion is assumed to have a yield of 1 KT and the nominal range is 6600 km. The frequencies of interest are rather low, 50 Hz and less, so absorption is small and the estimates of spectral character and duration essentially decouple. The spectrum depends almost entirely on the source characteristics and the duration is controlled by characteristics of the travel path. The airblast-induced pressure loading on the ocean surface dominates the source, with the acoustic waves from direct coupling into the water being relatively small. At large distances, the spectrum for 1 KT peaks near 20 Hz and is band-limited between 5 and 50 Hz. For different energy yields these frequencies scale with the cube-root of the yield. Different assumptions about the (laterally homogeneous) oceanic sound profile lead to differing estimates for the signal duration. Values of 20 to 60 seconds seem most reasonable.