The Hydroacoustic Network of the CTBT International Monitoring System: Access and Exploitation

ABSTRACT The hydroacoustic network of the International Monitoring System for verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty consists of six hydrophone array stations and five land-based seismic stations for recording T-phases. We provide a comprehensive overview of the network with details of the station configurations and data accessibility. Since 2014, data from all stations on the territory of Australia, the United Kingdom and the United States of America (four hydrophone arrays and one T-phase station) have been freely available, and we demonstrate how this data can be obtained and displayed with openly available software and minimal amounts of code. We detail which open seismic stations may act as limited surrogates for closed IMS stations. We demonstrate how the most fundamental characteristics of the hydroacoustic data can be obtained using open software, and we advocate extensive exploitation of this data for interpreting both hydroacoustic and converted seismic signals. We demonstrate signals from the 2017 North Korean nuclear test on both seismic and hydrophone data. Optimizing procedures using the open data allows us to explore the likely capability for all stations, even if real-time detection and processing outside the CTBT system is currently limited to hydrophone stations HA01, HA08, HA10 and HA11.