Description: The ability to negotiate and verify a Comprehensive Test Ban Treaty (CTBT) depends in part on the ability to seismically detect and discriminate between potential clandestine underground nuclear tests and other seismic sources, including earthquakes and mining activities. Regional techniques are necessary to push detection and discrimination levels down to small magnitudes, but existing methods of event discrimination are mainly empirical and show much variability from region to region. The goals of Lawrence Livermore National Laboratory`s (LLNL`s) regional discriminant research are to evaluate the most promising discriminants, improve our understanding of their physical basis and use this information to develop new and more effective discriminants that can be transported to new regions of high monitoring interest. In this report we discuss our preliminary efforts to geophysically characterize two regions, the Korean Peninsula and the Middle East-North Africa. We show that the remarkable stability of coda allows us to develop physically based, stable single station magnitude scales in new regions. We then discuss our progress to date on evaluating and improving our physical understanding and ability to model regional discriminants, focusing on the comprehensive NTS dataset. We apply this modeling ability to develop improved discriminants including slopes of P to S ratios. We find combining disparate discriminant techniques is particularly effective in identifying consistent outliers such as shallow earthquakes and mine seismicity. Finally we discuss our development and use of new coda and waveform modeling tools to investigate special events.
Date: July 1, 1995
Creator: Walter, W.R.; Mayeda, K.M. & Goldstein, P.
Partner: UNT Libraries Government Documents Department