SSA and AGU Update Position Statement on Comprehensive Nuclear-Test Ban Treaty

9 June 2022–In April, the Seismological Society of America (SSA) and the American Geophysical Union (AGU) agreed on minor updates to their position statement, “The Capability to Monitor the Comprehensive Nuclear Test-Ban Treaty (CTBT) Should be Expanded, Completed, and Sustained.”

The CTBT is an international agreement to ban all nuclear explosions, and is intended to impede the development of nuclear weapons as part of the international nonproliferation regime. The treaty is not yet in effect because it has not been ratified by all the requisite countries-including the United States.

The statement stresses that the global network of monitoring stations mandated by the CTBT must meet international goals for treaty verification and enforcement. The updates reiterate the network’s continued importance for national security, as well as to mitigation of earthquakes and other natural hazards.

“A high-quality and well-maintained global network of seismometers and other geophysical instrumentation is vital for detecting and characterizing both open and clandestine nuclear explosions, as well as earthquakes and other natural hazards, such as the explosion of the volcano Hunga Tonga-Hunga Ha’apai,” said SSA President Peggy Hellweg.

The International Monitoring System (IMS) negotiated under the CTBT consists of seismic, hydroacoustic, radionuclide, and infrasound networks. As of 2021, 326 of 377 IMS facilities were complete, and the seismological component of the system was more than 89% built and certified.

This seismological network can detect seismic events of about magnitude 4 or larger anywhere around the world, and to locate those events within 1,000 square kilometers (a circle with a diameter of approximately 35 kilometers), which is the maximum area permitted by the treaty for on-site inspection.

“The members of AGU’s seismology section want to restate the importance of the CTBT monitoring treaty. Data from the treaty’s International Monitoring System contributes not only to international security, but also to our collective scientific understanding of the Earth, including our ability to assess and mitigate hazards like earthquakes and volcanic eruptions,” said AGU Seismology Section leaders Suzan van der Lee of Northwestern University, and Martha Savage of the Victoria University of Wellington.

William R. Walter of Lawrence Livermore National Laboratory and Keith Koper of the University of Utah served as SSA reviewers for this update.

The Seismological Society of America and the American Geophysical Union originally issued the joint position statement on the seismic verification of the Comprehensive Nuclear Test-Ban Treaty (CTBT) in 1999. The statement was reviewed and reaffirmed by both organizations in 2003, 2007, 2012 and 2017 and was endorsed by the Geological Society of America in 2009.

SSA and AGU maintain position statements to provide scientific expertise on significant policy issues related to the understanding and application of their members’ scientific disciplines.