Analysis and interpretation of underwater acoustic data originated from the vicinity of the last known location of the Argentinian submarine ARA San Juan

Abstract

The CTBT International Monitoring System (IMS) is a world-wide network of seismic, infrasound, hydroacoustic, and radionuclide stations designed and deployed to detect nuclear explosions. Two of the IMS hydrophone stations, one in the Atlantic Ocean and one in the southern Indian Ocean, recorded signals of unknown nature which originated from the vicinity of the last known location of the San Juan submarine on 15 November 2017. To verify the accuracy of this hydroacoustic event localization, the Argentinian Navy successively deployed a controlled depth charge to the North of the last known position of the submarine. The signals from this source were also detected on the same two IMS hydrophone stations. Several techniques were employed to compare hydroacoustic features in the signals from the 15 November event and the controlled depth charge, including an assessment of spectral energy levels, cepstral analysis, azimuth and arrival time estimation of direct and reflected signals. This presentation compares the received signals, examines their main characteristics, and, through the use of acoustic modelling, identifies possible propagation paths between the source and receiver, including a plausible explanation of early arrivals hypothesized to follow propagation paths through the Antarctic ice sheet.