The long-range detection of an accidental underwater explosion

During the Shallow Water 2006 Experiment, SW06, a power supply for seabed-moored oceanographic equipment suffered an accidental explosion. The equipment was located on the New Jersey Shelf, 175 kilometers south-east of New York. Acoustic signals emitted by the explosion were detected by hydrophone sensors that form part of the International Monitoring System (IMS) of the Comprehensive Test-Ban Treaty Organization (CTBTO). The IMS hydrophones were located at Ascension Island, approximately 8,000 kilometers away from the explosion site. The signals received on the IMS hydrophones are described and their arrival times and azimuths compared with theoretical values derived from underwater acoustic propagation modeling. It is shown that the differences between predicted and observed values of arrival time are less than 2 seconds, indicating an error in travel time prediction of 0.04%. Measured azimuths are shown to be within 0.1 degrees of values derived on the assumption great circle propagation. While the explosion’s location was theoretically visible from other IMS sensors, it was only detected on the sensors at Ascension Island. The reasons for the absence of any other detection are discussed. The views expressed are those of the authors and do not necessarily reflect the views of the CTBTO Preparatory Commission.