An important technical issue associated with underground nuclear test monitoring is the discrimination of nuclear explosions from naturally occurring phenomena such as earthquakes and man-made disturbances such as mining explosions and rockbursts. Additionally, nuclear test ban treaty studies of seismic discrimination, yield estimation, and evasion have taught us the importance of explosion source-region phenomenology on monitoring capabilities. Los Alamos has undertaken a multidisciplinary effort involving the integrated analysis of ground-motion, seismic, and geologic data with calculations to improve our understanding of explosion source phenomenology and its effects on seismic signals. Earthquakes One of the fundamental technical problems in our work is the discrimination of underground nuclear explosions and earthquakes. Measurements can be taken from seismograms that are based on the expected differences between the two sources.
Explosions are compact, shallow sources with a very short time duration.
Because of their relative large spatial extent, earthquakes generally take more time to complete the rupture process than explosions. These dissimilarities result in differences in the ratio of P to S waves and spectral content between the two sources. In contrast, the early-arriving P waves from the explosion are enhanced relative to the surface waves. Specialized methods have been developed to integrate recorded ground motions, video, timing, local geology, velocity structure, and computer modeling used to analyze and interpret ground motion. UC2001 - For conditions of use, see Disclaimer .