A fully global hydroacoustic monitoring system for the Comprehensive Nuclear‐Test‐Ban Treaty—Plans and progress

The first ever fully global hydroacoustic monitoring system is being planned and implemented for use in the verification of a new international treaty, the Comprehensive Nuclear‐Test‐Ban Treaty (CTBT). This system will provide hydroacoustic monitoring of all the world’s oceans for 24 h a day, every day of the year, into the indefinite future. This unique resource will utilize two types of station. One type will be based on a hydrophone at the SOFAR axis depth, cabled back to shore. The other will be based on a seismometer on a small island using detection of the T‐phase signal. This latter station relies on a signal which has propagated predominantly through the ocean, but has been converted to seismic energy at the margin of the island. Although this network is being installed for monitoring of nuclear explosions, it will also be a unique resource for scientific investigation of various phenomena. Data will be available to all State Signatories to the CTBT.