UACE: In-water explosions recorded at the IMS hydrophone network from natural and anthropogenic events

• Day: June 16, Monday
    Location / Time: A. TERPSIHORI at 14:30-14:50
• Last minutes changes: -
• Session: 04. Comprehensive Nuclear-Test-Ban Treaty Monitoring, and its Civil and Scientific Applications
  Organiser(s): Georgios Haralabus, Mario Zampolli, Tiago Oliveira, Mark Prior
  Chairperson(s): Georgios Haralabus, Tiago Oliveira
• Lecture: In-water explosions recorded at the IMS hydrophone network from natural and anthropogenic events
  Paper ID: 2157
  Author(s): Tiago Oliveira, Mark Prior
  Presenter: Tiago Oliveira
  Abstract: The hydroacoustic component of the International Monitoring System (IMS) includes six stations deploying triplets of hydrophones suspended in the SOFAR channel. The oldest station in the network has been recording underwater sound since 2001. The roll-out of the network occurred progressively and concluded with the installation and subsequent certification of the Crozet Islands hydrophone station in 2017. This study evaluates the network's ability to detect and characterize in-water explosions via analysis of signals they generate. These are referred to in seismological terminology as ‘H-phases’. Data recorded from 2001 to 2025 are considered. The IMS data processing workflow at the International Data Centre (IDC) consists of two main parts: automatic processing and interactive analysis by human specialists, referred to as analysts. H-phases are automatically identified and reviewed based on signal characteristics, like the duration, spectral components, or spectral scalloping, which indicates a bubble pulse. Natural sources of H-phases detected at IDC include volcanic activity, while anthropogenic sources include marine seismic exploration and TNT charges. The study discusses natural and anthropogenic events that led to major detection peaks of H-phases in analyst-reviewed bulletins and analyzes how the increasing number of stations has improved the network's ability to detect and locate in-water explosions.
• Corresponding author: Mr Tiago Oliveira
  Affiliation: CTBTO
  Country: Austria