Regional Seismic Discrimination Optimization With and Without Nuclear Test Data: Western U.S. Examples Page: 4 of 12
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OBJECTIVES
Monitoring the world for potential nuclear explosions requires characterizing seismic events and discriminating
between natural and man-made seismic events, such as earthquakes and mining activities, and nuclear weapons
testing. We continue developing, testing, and refining size-, distance-, and location-based regional seismic
amplitude corrections to facilitate the comparison of all events that are recorded at a particular seismic station.
These corrections, calibrated for each station, reduce amplitude measurement scatter and improve discrimination
performance. We test the methods on well-known (ground truth) datasets in the U.S. and then apply them to the
uncalibrated stations in Eurasia, Africa, and other regions of interest to improve underground nuclear test monitoring
capability.
RESEARCH ACCOMPLISHED
As part of the overall National Nuclear Security Administration Ground-based Nuclear Explosion Monitoring
(GNEM) Research and Engineering program, we continue to pursue a comprehensive research effort to improve our
capabilities to seismically characterize and discriminate underground nuclear tests from other natural and man-made
sources of seismicity. To reduce the monitoring magnitude threshold, we make use of regional body and surface
wave data to calibrate each seismic station. Our goals are to reduce the variance and improve the separation
between earthquakes and explosion populations by accounting for the effects of propagation and differential source
size.
Western U.S Data Corrected for Magnitude and Distance Effects
We have been re-examining the large database of the western United States (U.S.) underground nuclear tests and
earthquakes we assembled under a prior year BAA (Walter et al. 2003). This western U.S. nuclear explosion data
covers a wide range of depths and material properties and has excellent ground truth information (Springer et al.
2002). This is unlike the situation in most of the world where regional recordings of nuclear tests are scarce and
discrimination optimization needs to be done in their absence. In addition we have chemical explosions recorded at
the same stations from the Arizona Source Phenomenology Experiment (AZSPE). The AZSPE carried out
dedicated single shot chemical explosions under a variety of depth and confinement conditions in two mining
regions, a soft rock coal mine and a hard rock copper mine (see Bonner et al. this volume). These mining regions
also routinely detonate ripple-fired production blasts that can be observed at regional distances. The availability of
both nuclear and chemical explosions lets us examine the differences in optimization and performance of the two
source types relative to the earthquakes. The locations of the data and stations discussed in this paper are shown in
Figure 1.
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Walter, W. R.; Mayeda, K.; Gok, R.; Rodgers, A. J.; Sicherman, A.; Hickling, T. et al. Regional Seismic Discrimination Optimization With and Without Nuclear Test Data: Western U.S. Examples, article, June 30, 2005; Livermore, California. (https://digital.library.unt.edu/ark:/67531/metadc876038/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.