American Geophysical Union Statement on Monitoring the Test Ban Treaty

At a morning press conference today, the American Geophysical Union and the Seismological Society of America released the following position statement:

American Geophysical Union and Seismological Society of America Joint Position Statement

Capability to Monitor the Comprehensive Test Ban Treaty

“In September 1996, the United States was the first of 152 nations to sign the Comprehensive Test Ban Treaty (CTBT), an international agreement to ban all nuclear test explosions. The treaty is intended to impede the development of nuclear weapons as part of the international nonproliferation regime. The treaty has not yet been ratified by the U.S. As a result, many of its verification provisions have not yet been fully implemented. When implemented, the American Geophysical Union (AGU) and the Seismological Society of America (SSA) are confident that the combined worldwide monitoring resources will meet the verification goals of the CTBT.

“The CTBT will be monitored by: 1) the national intelligence means of various countries, 2) the International Monitoring System (IMS) negotiated under the CTBT that consists of seismic, hydroacoustic, radionuclide, and infrasound networks, along with on-site inspections,and 3) the efforts of numerous independent scientists and institutions worldwide. It is this combination of resources that gives confidence in the ability to uncover CTBT violations. AGU and SSA believe that this overall monitoring capability will continue to strengthen as more data are collected, more research is performed, and as global communication networks expand. The seismic component of the International Monitoring System is to consist of 170 seismic stations. This network is expected to detect all seismic events of about magnitude 4 or larger and locate those events within 1000 square kilometers (a circle with a diameter of approximately 35 km). This is the maximum area permitted by the treaty for an on-site inspection. A seismic magnitude of 4 corresponds to an explosive yield of approximately 1 kiloton (the explosive yield of 1,000 tons of TNT). AGU and SSA believe that the verification system, if built as planned, can be relied upon to meet that goal.

“One of the biggest challenges to monitoring the CTBT is the possibility that testing could be successfully hidden by conducting nuclear explosions in an evasive manner. The concern is partly based on U.S. and Russian experiments which have demonstrated that seismic signals can be muffled, or decoupled, for a nuclear explosion detonated in a large underground cavity. The decoupling scenario, however, as well as other evasion scenarios, demand extraordinary technical expertise and the likelihood of detection is high. AGU and SSA believe that such technical scenarios are credible only for nations with extensive practical testing experience and only for yields of at most a few kilotons. Furthermore, no nation could rely upon successfully concealing a program of nuclear testing, even at low yields.

“Data from the treaty’s monitoring system will also contribute to our scientific understanding of the Earth and efforts to mitigate earthquake hazards. Article IV.A.10 of the treaty states ‘The provisions of this treaty shall not be interpreted as restricting the international exchange of data for scientific purposes’. AGU and SSA support a broad interpretation of this article and strongly urge that all data from the International Monitoring System be made openly available without any restriction or delay.”

In opening the press conference, AGU Executive Director Dr. A. F. Spilhaus Jr. explained that the statement was intended to “inform public policy debate.” This is the first time AGU has issued a joint statement, and the first time that SSA has issued such a statement. The two societies represent approximately 4,000 seismologists.

Three speakers explained the process and the rationale behind the statement. Dr. Terry Wallace, SSA president and professor at the University of Arizona, told reporters that the statement was drafted over the last year, and is a technical assessment of the monitoring system. Verification seismology has been used since 1957. Dr. Jeffrey Park, professor at Yale University, commented on changes in seismological verification over the last forty years in the ability of scientists to detect very small explosions. While noting that there will always be some explosive level at which verification will not be possible, Park explained that seismology is but one component of a multi- faceted verification system. Dr. Gregory van der Vink, Director of Planning for IRIS, and a visiting professor at Princeton, explained how existing and planned seismological stations would be capable of detecting treaty violations. Van der Vink was a member of the Arms Control and Disarmament Agency’s Red Team that evaluated the monitoring system for the Comprehensive Test Ban Treaty.

On Capitol Hill, the Senate’s leadership is backing away from plans to hold a ratification vote on the treaty next week. Reports indicate that the treaty would not be taken up until after the next election. In testimony before the Senate Armed Services Committee today, Defense Secretary William Cohen told senators that “If the Senate rejects the treaty, the proliferation of nuclear weapons is more likely, posing serious challenges to our non-proliferation goals.”