Inclusion of three dimensional acoustic propagation in nuclear event characterization

Abstract

The verification regime of the Comprehensive Nuclear-Test-Ban Treaty is the International Monitoring System that includes deep-water hydroacoustic stations for monitoring the world oceans for nuclear tests. As underwater sound propagation satisfies the acoustic wave equation, it is subject to three-dimensional (3D) effects (refraction, diffraction, reflections) when in the presence of horizontal gradients due to bathymetry, oceanography, or the presence of continents. The current processing system does not exploit these 3D effects, because it relies on in-plane propagation for all acoustic paths, which may lead to azimuth errors for event association. In this work, a set of acoustic propagation codes are being proposed to integrate 3D propagation into the automated event localization algorithm as well as into the analyst work flow. A summary of the acoustic models, demonstrations of observed 3D phenomenon for large underwater events, as well as a program plan to update the processing scheme will be presented.