WASHINGTON -- The American Geophysical Union (AGU) and the Seismological Society of America (SSA) will issue a position statement on the capability to monitor compliance with the Comprehensive Test Ban Treaty (CTBT) at a press conference on October 6 at 10:00 A.M. EDT at AGU headquarters in Washington, D.C. You are invited to attend.

The United States signed the treaty in September 1996, but has yet to ratify it. The U.S. Senate is expected to debate and vote on ratification this month.

Three seismologists who participated in drafting the position statement will be present to answer questions about it. They are:

Dr. Terry C. Wallace of the University of Arizona in Tucson, who chaired the drafting committee. Wallace is President of SSA and a Fellow of AGU.

Dr. Jeffrey J. Park of Yale University. He is a member of the AGU Council (governing body) and President-elect of AGU's Seismology Section.

Dr. Gregory E. van der Vink, Director of Planning for the Incorporated Research Institutions for Seismology (IRIS) and a member of AGU's Committee on Public Affairs.

Date: October 6, 1999
Time: 10:00 A.M. EDT
(The room will be available from 8:00 A.M. for camera setup.)
Place: American Geophysical Union
2000 Florida Avenue, N.W.
Washington, D.C. 20009

AGU is an organization of 35,000 members engaged in the earth and space sciences. SSA is an international association devoted to the advancement of earthquake science.

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.