May/June 1998


On September 24, 1996, President Clinton signed the Comprehensive Test Ban Treaty (CTBT) at the United Nations (UN), calling it "the longest-sought, hardest-fought prize in the history of arms control." This treaty bans all nuclear weapon test explosions and any other nuclear explosions anywhere in the world, of any size, and at any time in the future--a complete "zero-yield" ban on nuclear testing. Indeed, it is a crowning accomplishment of over forty years of bipartisan arms control efforts in the United States, beginning in the 50s with the Eisenhower administration. Over 145 countries have now signed the CTBT, a global endorsement of political support with a pledge to abide by the terms of the Treaty until it becomes international law. Before this happens, 44 countries with nuclear capabilities, either in reactor technologies, research, or weaponry, must ratify the Treaty and submit instruments of ratification to the UN Secretary General. Three of these countries, India, Pakistan, and North Korea, have not yet signed the Treaty.

Spotlight on the struggle for a CTBT now shifts to national arenas. Each country must decide for itself whether risks to national security are outweighed by the benefits of the Treaty. Nowhere is the spotlight stronger than on debate taking place in this country, within the halls of the United States Senate, where President Clinton submitted the CTBT for advice and consent to ratification last September. Senate hearings are underway, and a vote could come sometime this year. Many countries around the world, including Russia and China, are waiting to see what happens in the United States before taking actions of their own.

In this opinion, I summarize key issues of our nation's debate on CTBT ratification. Obviously, treaty verification is an important national issue, and most seismologists are aware of the major role our science plays in monitoring a CTBT. Another key issue concerns nuclear weapon stockpile stewardship for maintaining a nuclear deterrent under a CTBT. Verification and nuclear stockpile stewardship can be viewed as opposite sides of the same national security "coin," and I discuss both in this article. I give perspectives on seismology's past and present role in treaty monitoring, and I discuss the benefits of federal support for monitoring research and for geophysics in general. The importance of continued funding for research and development (R&D) of monitoring technologies must be stressed to our government leaders. It is incumbent upon citizen scientists to be involved in the ratification debate, and I conclude with a call for our views to be heard, as individuals and as a professional society.


The importance of a CTBT for arms control and non-proliferation cannot be overstated. The Treaty will constrain development of new nuclear weapons by the existing weapon states (United States, Russia, China, Britain, and France) and by so-called nuclear threshold states (e.g. Israel, India, Pakistan). Non-nuclear states will be discouraged from developing nuclear weapons programs because of the constraints imposed by the inability to test and/or by the high monetary (and potentially political) costs of carrying out a clandestine nuclear program. The CTBT is also a keystone for a stable non-proliferation regime since it will demonstrate the commitment of nuclear weapon states to the Non-Proliferation Treaty (NPT) and to disarmament in general. In 1995, all states parties to the NPT, including the five nuclear weapon states, pledged to complete a CTBT by the end of 1996 as part of an agreement to extend the NPT indefinitely into the future. It is now crucial that these five weapon states demonstrate leadership by speedily ratifying the CTBT. This will serve to solidify global commitment to non-proliferation by reassuring non-nuclear states that the `95 decision at the NPT Renewal Conference was sound.

Like the fight for ratification of the Chemical Weapons Convention in the Senate, CTBT ratification will be a tough, uphill struggle. Much of the debate will focus on two key concerns: (1) Can we maintain the safety, security, and reliability of our nuclear deterrent without testing? and (2) Can we effectively monitor compliance with the Treaty worldwide? Provisions were written into the CTBT for establishing international capabilities to monitor explosions in all testing environments. While these provisions help to address concerns in this country about monitoring compliance, ensuring the viability of our nuclear deterrent is a huge national issue that must be resolved in the Senate for there to be any hope of passage. Before describing monitoring provisions of the Treaty, I briefly summarize how the concerns in (1) are being addressed. This will serve to illustrate a number of issues surrounding CTBT ratification of which we should be aware.


The Science-Based Stockpile Stewardship (SBSS) program was developed by the Department of Energy (DOE) in conjunction with the Lawrence Livermore, Los Alamos, and Sandia National Laboratories to provide information for evaluation and certification of our nation's nuclear deterrent for the indefinite future. With input from the directors of these three laboratories, the secretaries of the Departments of Defense and Energy must certify to the President on a yearly basis that our nuclear deterrent remains safe, sound, and reliable. In about ten years, all nuclear weapons in the United States arsenal will have exceeded their designed lifetime. The SBSS program thus addresses the special concerns associated with an aging stockpile of nuclear weapons. For example, radioactive decay of fission materials within a warhead may affect other components, impacting safety and performance. Components from deployed weapon systems are to be returned to the laboratories periodically for disassembly and inspection. If defects are found, assessments are made of their impact on safety and performance, and, if necessary, the part is re-manufactured and replaced. Assessments draw upon results of computer simulations, laboratory tests, and databases compiled from past nuclear explosions. The SBSS program also maintains a cadre of technical expertise on nuclear weaponry should there be a need for the United States to withdraw from the Treaty for national security concerns, as provided for under Article IX of the Treaty, and to resume nuclear testing.

Nuclear scientists in and outside the weapons establishment have reviewed the SBSS program and its costs. It is generally accepted that the program will achieve its goals, if bipartisan support for funding continues in the years ahead. A number of critics have voiced strong reservations about cost, and about the possibility that militarily-significant modifications of current weapon systems could be made, and designs of nuclear weapons could be advanced under the SBSS program. They argue that funds should be directed only at present stockpile maintenance and that basic research leading to new weapon development be prohibited. Advocates of SBSS point out that the program costs less than weapon development and production during the cold war years and that any significant modifications or new designs would require testing before deployment. Hence, such modifications or developments would not be possible under a CTBT.


Much work went into formulating the Treaty provisions for monitoring compliance in all testing environments: underground, underwater, in the atmosphere, and at the boundaries of these environs. Four technologies are drawn upon in a global network of sensors: seismic, hydroacoustic, infrasound, and radionuclide. This network, called the International Monitoring System (IMS), consists of 50 primary seismic stations and 119 auxiliary stations, 11 hydroacoustic stations, 60 infrasound stations, and 80 radionuclide stations. The primary seismic stations transmit data continuously for initial detection, location, and identification of events occurring underground and in some cases underwater; auxiliary stations provide data upon request for events detected by the primary stations and in need of further refinement of location and identification. Hydroacoustic stations are of two types also, six deployed as primary detectors for underwater events or events occurring close to the water-air, water-land interfaces, and five so-called "T-phase" stations deployed on islands to detect phases generated by acoustic waves coupled into the solid Earth. Infrasound stations measure low-frequency acoustic waves in the atmosphere from explosions detonated above or close to the air-water or air-land interfaces and are the primary means of detecting explosions in the atmosphere. Radionuclide sensors detect particulates and gas by-products of nuclear explosions detonated in the atmosphere and underground. These data will be used for detection and for positive identification of a nuclear explosion. All sensor data generated by the IMS are to be unclassified and open to the scientific community. Indeed, availability of the data on a timely basis is crucial to meeting the scientific interests of the community.

In addition to the IMS, the CTBT provides for the following: (1) consultation and clarification procedures, (2) on-site inspections, and (3) confidence-building measures. The Treaty establishes the Comprehensive Test Ban Treaty Organization (CTBTO) to oversee implementation of the Treaty and its verification regime. The objective of consultation and clarification is to allow states parties the opportunity to resolve questions about treaty compliance before having to resort to on-site inspection. If questions cannot be resolved, an on-site inspection may be requested by a state party. If the request is judged to be warranted by the Executive Council of the CTBTO, technical teams may enter the territory of another party where the suspicious event occurred for the purpose of confirming the nature of the event. The size of the territory searched may not exceed 1000 km2 and investigative procedures, such as drilling, are spelled out in the Treaty protocols. Confidence-building measures are intended to reduce the ambiguity and uncertainty that may be associated with some events detected by IMS sensors. Such measures might include voluntary information exchanges or calibration experiments for improving IMS location and identification capabilities.

The United States has other resources at its disposal for augmenting monitoring capabilities provided by the Treaty. These resources include national technical means (NTM), such as satellite imagery, and diplomatic measures. The Treaty provides that information gathered by NTM can be submitted to the CTBTO as evidence to support a request for an on-site inspection.

Despite these monitoring provisions and enhancements, we will not be able to verify a "zero-yield" CTBT with complete confidence. Signals from very small tests may go undetected by the IMS. Because of the limited technical benefits of small tests, such violations of the Treaty are not considered to be a major threat to the United States or international security. Also, the risks of being detected are high, which serves to deter potential evaders. This is particularly true for seismic detection since large numbers of observatories are operated around the world by research institutions for investigating Earth's seismicity, internal structure, and seismic hazard. Signals from clandestine tests may be recorded by stations of these independently-run observatories. While these observatories are not formally part of the IMS network, their data should prove useful in clarifying ambiguous events.

The IMS will generate a huge amount of digital sensor data transmitted in real time or later upon request to the International Data Center (IDC) in Vienna, Austria for processing and analysis. The main product of the IDC will be a reviewed event bulletin (REB) containing estimates of the location, origin time, and size of events. Final REBs will be generated about two days after the event's occurrence, although preliminary location estimates will be available within hours of the event. In addition, National Data Centers (NDCs) will be established by states parties; they will collect data from in-country stations belonging to the IMS and forward data to the IDC. These centers can request data from the IMS and will receive REBs, although some NDCs may generate their own bulletins. NDCs are responsible for making assessments of the nature of the event, not the IDC. The United States NDC is located at Patrick Air Force Base in Florida and is operated by the Air Force Technical Applications Center (AFTAC).


Seismology plays a major role in monitoring the CTBT, since it is the primary technology for detecting, locating, and identifying events in the solid Earth. The importance of seismology has been known since initial discussions of test bans with the former Soviet Union in the 1950s. What wasn't appreciated at the time was the difficulty of verifying a complete test ban. The challenges for seismic monitoring quickly became apparent in the late 50s and early 60s when the Limited Test Ban Treaty (LTBT), banning all atmospheric tests, went into effect and testing moved underground. Seismic data for early underground tests showed that signals from small explosions would be hard to detect and even harder to discriminate from earthquake signals than originally thought. The implications for CTBT monitoring were devastating. These discoveries precipitated the largest programmatic build-up in the history of seismology. R&D programs supported basic research of wave propagation and seismic sources (explosions and earthquakes), and funded technology development of seismic instrumentation. For example, one of the major accomplishments of the Air Force's Project Vela Program was the installation of a global network of standard seismographic stations, called the World-Wide Standard Seismological Network (WWSSN). Data from the WWSSN provided an "explosion" of new information for treaty monitoring research and played a major role in discoveries leading to the geosciences revolution in the 60s with the advent of plate tectonics and much-improved knowledge of the Earth's internal structure.

In the 80s and 90s, we have witnessed yet another revolution, the technological revolution of digital seismology. This was triggered in part by a confluence of research interests over the rich information content of signals recorded on wide frequency-band sensors at regional distances (200 - 2000 km). For example, studies of broadband regional waveforms provide information about fine structure of the Earth's lithosphere, which is important for further understanding of plate tectonics. For treaty monitoring, broadband data offer the promise of improved detection and identification of small-magnitude events. Assessments of operational demands on a global network for monitoring a CTBT were made by a series of international data exchange experiments, the so-called GSETT experiments (Group of Scientific Experts [GSE] Technical Tests), coordinated by the GSE under the UN's Conference on Disarmament in Geneva. These assessments, along with the use of high frequency data, established a need for digital technology, including low-noise seismometry, wide-bandwidth, satellite telemetry, high-performance computers, and massive data storage technologies.

The challenges of monitoring a CTBT remain daunting even after forty years of advances in our understanding of seismic sources and wave propagation in the Earth. Many of the difficult problems today were identified in the early days of monitoring research: detection and identification at low magnitudes, accurate determination of event location, and better monitoring methods to counter nuclear test evasion, such as seismic decoupling. A major task for seismology and the other monitoring technologies today is calibration of the IMS and NTM to ensure that monitoring functions, such as detection, location, and identification, are effective. Calibration will be accomplished largely through empiricism, and this poses a challenge for wave propagation studies because the Earth's structure can be so heterogeneous on regional scales important for monitoring. Another new research area is development of methods exploiting the synergies among technologies, as the monitoring capability of the IMS as a whole should exceed the combined capabilities of its constituent parts.

The need for continued funding of treaty monitoring R&D remains high, since many problems must be solved on basic, applied, and operational levels before full monitoring potential of IMS and NTM systems can be realized. The work is currently split between universities, industrial contractors, and national laboratories. Traditionally, universities are centers for innovative studies and knowledge acquisition critical to treaty monitoring. In the past few years, we have witnessed funding cutbacks for basic R&D in the geosciences, and these cuts have affected monitoring research at the universities. If this trend continues unchecked, future technological development for improved monitoring capabilities will be seriously impacted.


The fight for ratification in the United States Senate is expected to be very contentious. Many senators may hold off their decision until the conclusion of debate, which would leave their decisions more susceptible to political "arm twisting" and outcome of the final vote thus more unpredictable. This could be disastrous for successful conclusion of the CTBT, ironically when there seems to be general belief among the populace that it is time to push arms control treaties on many fronts and put the cold war mentality behind us.

Key to prompt ratification is the willingness of the Clinton administration to avoid partisan politics, to shape the debate over a CTBT early and often, to define the consequences should ratification fail, to enlist vigorous support from prominent national and international leaders, and to work closely with Senate majority leader, Trent Lott. Shaping the debate early and often, while lining up bipartisan support from past and present national leaders, will solidify support for the Treaty and avoid "11th hour" politicking. However, both parties must avoid partisan politics, which may be difficult in the present Senate. Prior to the President's State of the Union address, in which CTBT ratification in 1998 was highlighted, Senator Jesse Helms wrote Clinton that the CTBT was too low a priority to be considered this year. As chairman of the powerful Senate Foreign Relations committee, the Republican senator from North Carolina has set the ultra-conservative's agenda, putting consideration of NATO membership, the Kyoto Protocol, and amendments to the ABM Treaty first. In this way, the CTBT may be held "hostage" by the reactionary right, foiling Clinton's plans for ratification in the near future.

To successfully press for CTBT ratification, it is necessary that governmental leaders hear the views of the public at large. As seismologists, we offer unique perspectives on the Treaty, regardless of whether we have done treaty monitoring research. Some of us may have the opportunity to provide expert testimony in Senate hearings, but all may exercise the right to voice their opinions to government representatives. It is also important for the SSA to take a position and make sure it is heard. I strongly urge the Board of Directors to draft a position statement on CTBT ratification for the society. This statement should be made available to SSA members for comment. All members should read it and provide feedback on a timely basis. We can make a difference through our personal and professional endeavors on a very important issue of our time.

For further information about CTBT ratification and technologies in support of treaty monitoring, I encourage you to visit the DOE CTBT R&D Program web site at www.ctbt.rnd.doe.gov. This location provides full treaty text and linkages to other CTBT-related governmental web sites.

Howard J. Patton, Geophysics Group
Earth and Environmental Sciences Division
Los Alamos National Laboratory

The views expressed in this article are those of the author, and do not represent those of the United States Government nor any agency thereof.

To send a letter to the editor regarding this opinion or to write your own opinion, contact Editor John Ebel by email or telephone him at (617) 552-8300.

Posted: 26 June 1998