Comments to the Seismological Community

The Honorable John D. Holum,
Director, U.S. Arms Control and Disarmament Agency

As an arms control official, I am probably not the consumer you typically envision. But in a larger sense arms control has been the direct beneficiary of a series of remarkable advances in your field in the decades since Gutenberg published his papers on the Trinity and Baker tests in the 1940's, and the Berkner Panel released its report in 1959. From the time of the Limited Test Ban Treaty in 1963, seismology has cemented its primary role.

Since then, supported by the U.S. Government, you and your predecessors have made great progress in event detection, location, and identification - giving us truly sensitive seismic arrays and forensic seismology techniques of extraordinary utility. And we are gaining access to new realms of information from regional distances and even to data from close-in seismometer networks.

Your strides in pushing the seismic state of the art have already made substantial contributions to arms control and our national security. They provided a significant part of the basis for President Clinton's 1993 decisions to continue the testing moratorium and pursue a test ban treaty. They helped give us the requisite confidence to embrace a true zero-yield treaty last year. Historically, verification has been a major stumbling block for the CTBT, and during the past 2 years in Geneva, it was the most time-consuming issue to resolve. As you know, the CTBT text presented in New York will set in place a new global information-gathering and -processing regime. Its International Monitoring System will include four distinct systems of sensors: seismic, radionuclide, hydroacoustic, and infrasound. Their data will be fed to the International Data Center, to be compiled, analyzed, combined with other data, and shared.

The CTBT will provide for a far-flung global network of fifty primary seismic stations - either highly-capable arrays, or in some cases capable three-component single seismometers - distributed so that the basic event detection capability will be significantly below a seismic magnitude of four, or roughly one kiloton fully-coupled in hard rock. For many places on the globe, the event detection threshold for the prototype system is routinely about seismic magnitude three - roughly equivalent to an explosion of some 50-100 tons fully-coupled in hard rock.

To help localize seismic events, the IMS will also provide for a network of 120 auxiliary stations. Many of these are multiple-use stations designed for general geophysics purposes. Together, the primary and auxiliary seismic networks will seek to localize seismic events to 1,000 square kilometers or less - an area sufficiently small to permit an on-site inspection with some reasonable prospects for success.

In addition, a network of eighty radionuclide sensors will provide further information - and deterrence - against atmospheric or underground testing attempts. Because many natural seismic events occur under the oceans, a hydroacoustic network is also being established to assist in discriminating such events from nuclear explosions. And the network of infrasound (or very low-frequency acoustic) sensors will detect and deter atmospheric explosions, particularly in the remotest regions.

We intend to process all the data collected centrally by the IMS. Identifying an event as a nuclear explosion is a task left to the Treaty parties themselves. Of course, we are not limited to the IMS. The Treaty text permits States Parties to provide supplementary data to the IDC from national monitoring stations outside the IMS which could be used either to raise or answer questions about a specific event. The Treaty also supports the international exchange of data for scientific purposes, and promotes cooperation among States Parties to strengthen Treaty implementation. And it provides for confidence-building measures, including information-sharing about large chemical explosions.

Most importantly, the Treaty spells out the right of States Parties to make use of national technical means - provisions the United States made clear were indispensable, despite the opposition of several countries. Thus we will be able to draw on assets not specified in the IMS, including seismic, hydroacoustic, and satellite means of detecting nuclear explosions.

We intend to integrate our national data along with that collected centrally by the IMS, in our own ongoing monitoring against any potential evader of the CTBT. When we do this, we expect the whole to exceed the sum of its parts. Our aim is a national capability that will meet our own standards for event detection in all environments.

All of this brings us to the bottom line question: as my Agency performs its statutory responsibility to report to the Congress on the verifiability of arms control treaties, what will we say about the CTBT? We are still working on a final assessment. But we've been engaged for more than two years in a rolling assessment as the text evolved. I expect a conclusion that this Treaty will meet our baseline standards for detecting and deterring violations. Obviously we should not count on detecting events all the way down to zero explosive yield by remote sensing alone. But even down to very low yields, a potential evader runs the risk of detection - and at any yield he runs the risk of being exposed by other means, and being subject to an on-site inspection.

Taken together, the IMS and its International Data Center, the other geophysical sensors spread around the world, the United States' own sensor systems, other national means, plus the prospect of prompt on-site inspections, will create a risk of detection that a potential violator will not be able to calculate with any precision. That, and the prospect of global sanctions upon being found out, will create a powerful deterrent against violations.

You deserve America's gratitude for this - and more. You deserve the most stable funding and rational supervision of your efforts that our country can provide. Now that we have signed a CTBT, it is no time to dissipate or take for granted the unparalleled expertise we have cultivated in your field. For your work is not done. In announcing the zero-yield decision of August 1995, the President said: "I recognize that our present monitoring systems will not detect with high confidence very low-yield tests. Therefore, I am committed to pursuing a comprehensive research and development program to improve our treaty monitoring capabilities and operations."

Your efforts are vital to this program. So I am heartened to see how much of your work is addressing practical monitoring needs, such as: work on the crustal geology of regions such as South Asia, the Middle East, the Korean Peninsula, and China; efforts to calibrate specific areas; the development of enhanced algorithms and calculational methods to help us understand data collected at regional distances; valuable empirical work on characterizing mining blasts; investigations of effective discriminants such as the Lg phase; refinements in epicenter determination; and a variety of efforts to understand and build forensic synergies between our dedicated national assets and other seismic stations - and most broadly, between seismic and other detection techniques.

Such work is already enhancing our considerable abilities to monitor nuclear testing worldwide. I know you will not rest until the President's call for high confidence even at very low yields is answered. So as the Treaty prevails and its history is written, your contributions will earn a lengthy chapter and an honored place. I thank you for that, and for all your work here to help advance a leading priority of President Clinton, and a profoundly important global mission.

[These comments were modified from remarks by the Honorable John D. Holum at the 18th Annual Seismic Research Symposium on "Monitoring a Comprehensive Test Ban Treaty,", sponsored by Phillips Lab, AFOSR, AFTAC and DOE and held at Lowes Annapolis Hotel, Annapolis, Maryland, September 6, 1996.]

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