Underground Nuclear Explosion Monitoring and Discrimination

Underground Nuclear Explosion Monitoring and Discrimination

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Credit:
D.S. Dreger, S.R. Ford, and W.R. Walter/AAAS

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Description

Identifying near-surface seismic sources (discrimination) is a critical problem that has advanced through decades of research and development of both analytical methods and instrumentation. As the discipline has advanced, seismology has achieved robust quantitative discrimination capabilities for various source processes from remote seismic recordings. Most notably, it is possible to distinguish signals generated by underground collapses, earthquakes, and nuclear and other explosions. Shown in the figure are example events mapped according to the relative magnitude of their moment tensor elements (force systems that describe the source type) estimated from seismogram waveform inversions. (Image modified from D.S. Dreger, S.R. Ford, and W.R. Walter, 2008. Source analysis of the Crandall Canyon, Utah, mine collapse, Science, 321(5886):217, doi:10.1126/ science.1157392. Reprinted with permission from AAAS).

Seismology plays a key role in the detection and characterization of nuclear explosions and their discrimination from earthquakes and other types of explosions. Development of the discipline of seismology has been greatly facilitated by the critical geopolitical need to monitor underground nuclear testing conducted at shallow depth in the crust. This mission led to the establishment of the first modern global seismographic network, the World Wide Standardized Seismographic Network (WWSSN), which operated over 100 stations in dozens of nations in the 1960s and 1970s, as well as subsequent global digital seismic networks. The nuclear test monitoring issue has prompted investments in the IRIS/USGS Global Seismographic Network (GSN), the United Nations Comprehensive Test Ban Treaty Organization (CTBTO ) International Monitoring System (IMS), and U.S. Department of Defense monitoring efforts managed by the Air Force Technical Applications Center (AFTAC ), along with additional government, academic, and private seismic networks worldwide. Data from many of these efforts (the IMS is an unfortunate notable exception) are openly available in real time via national or regional data centers to facilitate rapid scientific and forensic analysis of anthropogenic and unusual natural events. Operational and basic research in support of nuclear monitoring is carried out by a worldwide contingent of seismologists in universities, national laboratories, and government agencies. These extensive data and research activities have produced advanced capabilities in seismic monitoring, particularly the ability to reliably discriminate signals from small nuclear explosions amidst a background of signals from earthquakes and other natural sources. Whether the CTBT formally enters into force or not, seismology will continue to play a critical role in monitoring of nuclear testing treaties and underground explosion activities worldwide.

Date Taken: February 18, 2009
Photographer / Contributor: D.S. Dreger, S.R. Ford, and W.R. Walter, 2008.

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Seismological_Grand_Challenges, Long_Range_Science_Plan,

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