Chapter 6: Summary and Recommendations

Developing a New Solution

For decades, the United State´s first priority was to contain aggressive Soviet power. Proposals for reduced-threshold testing treaties or a CTBT were evaluated in the context of U.S./USSR competition. Today, the spread of nuclear weapons is a much more ominous problem, and the new task is one of monitoring a CTBT in the context of non-proliferation. We cannot simply apply the old strategy of monitoring particular areas down to a specific threshold at high confidence. Rather, we must develop a new strategy for monitoring globally and for increasing confidence that no nuclear test could go undetected. This requires a fundamental change in how we apply and develop seismological resources.

With the past emphasis on the unilateral monitoring of specific test sites, monitoring was based on single-component narrow bandwidth, arrays that recorded only vertical ground motion in the frequency range of 1-10 Hz. Such arrays could be tuned to specific test sites and were well suited to the detection of teleseismic waves traveling great distances through the geologically stable Russian continental platform. Accumulated knowledge of testing practices minimized concern about discrimination between nuclear explosions, industrial explosions, and earthquakes; and thus there was little need to develop additional methods for identifying seismic events.

Today, monitoring can be done on a multi-lateral basis with open sources of data and international cooperation. The emphasis is no longer on known test sites, but on the accurate location and discrimination of low-magnitude seismic events in areas where testing may have never occurred previously. Accordingly, we need to change our monitoring emphasis from teleseismic waves (those that travel distances greater than around 1500 kilometers) to regional waves that generally travel less than 1000 kilometers. Regional waves, however, are complex and easily influenced by how and where the seismic event occurred, and the material and structure through which the seismic waves travel. To understand these waves, we must use broad bandwidth, three-component seismic instruments that can reconstruct the complete ground motion through a broad range of frequencies. Such data are critical for improving our understanding of regional wave propagation and developing new methods for identifying nuclear explosions using regional waves.

To a large degree, the monitoring task is being assisted by new developments in seismometer design, low power electronics, computers, and communication technology. Ground motions can now be recorded by single instruments over the complete range of frequencies and amplitudes useful to seismology. Global communications and the expanding computer communication networks now allow the rapid transfer of seismic data from remote sites. Monitoring can be further assisted by both the technical and intellectual resources that are being applied in other areas of seismology.

Global seismic monitoring has direct application not only for treaty verification, but also for the recording of earthquake activity, the assessment of seismic risk, and in the scientific exploration of the Earth´s interior. The same underlying scientific principles and many of the techniques used in data analysis are common to each of these applications. With recent advances in seismic instrumentation, the needs for all these applications can be met by the same equipment. There no longer need be major distinctions between an "earthquake station" and a "nuclear monitoring station", thus opening opportunities for collaboration and considerable cost savings. Stations with multiple applications will increase not only the data available for monitoring purposes, but also increase the number of scientists that assist indirectly in the monitoring task. By incorporating all of these stations into the monitoring effort, the redundancy of coverage will provide data validation and high reliability. The open source of data and increased number of scientists using the data will create the technological equivalent of a global "neighborhood watch" program.

Nuclear Testing and Nonproliferation

Return to:Table of Contents
Return to:Chapter VI, Seismology's Role in Deterring Proliferation
Continue to:Chapter VI, Capabilities of Seismic Monitoring