Underwater explosions recorded at IMS hydroacoustic stations from well-defined experiments

This study analyzes signals recorded by the CTBT-IMS hydroacoustic network from well-defined underwater explosions in the Atlantic Ocean, and looks at the relationships between yield, location, and detectability. The events analyzed are detonations of TNT charges and are used here to assess the ability of the CTBT-IMS hydroacoustic network to detect H-phases, which are signals from in-water explosions. The locations of the explosions ranged between the continental shelf, shelf break, and deep waters, and their yields were between 0.8 and 18,000 kg TNT. For high-yield explosions, T-stations (coastal seismometers) and Hydrophone stations effectively detected the explosions. For distant low-yield events, the ability of the network to detect the explosions depends heavily on the location of the source. Distant shallow events on the continental shelf can be more detectable than closer deep-water events. This is because the sound from the former events propagates off the shelf and skips off the shelf edge into the SOFAR channel, while events in deep water, depending on their depth, can have more difficulty coupling into the SOFAR channel. Similarly, explosions near the shelf break can have a favourable SOFAR channel coupling mechanism due to reflections from the shelf into the channel.