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Study of Broadband Lg/P and its Application to Source Discrimination,

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Several investigations have shown the ratio LgP to be an effective regional discriminant, but its limitations and spectral characteristics under various geological settings and near-source parameters are largely unknown. This research will analyze representative sets of broadband three-component data for regional phases Pn, Pg, Sn, Lg, and Rg from both explosion and earthquake sources belonging to several distinct regions. The main sources of data will be the large amount of regional, near-regional, and near-field data available from several Department of Energy Labs and the primary Alpha and auxiliary Beta stations of the GSETT-3. A considerable amount of in-country regional data from seismic sources with ground-truth information is also available from the former USSR. These data include not only shots with large variations in their near-source parameters such as geology, yield, and depth of burial but also a few decoupled shots, so their analysis will provide an improved understanding of the role of various near-source parameters in shaping the broadband characteristics of regional phases. Data from decoupled shots, identification of which perhaps constitutes the greatest challenge to U. S. efforts, will be used to investigate whether such explosions may be identified on the basis of their relative deficiency in higher frequency S or Lg. The mechanism of generation of Lg and its influence on the ratio LgP will be determined by using several methods, including synthetic seismograms and finite-difference investigations. Results of the study will significantly improve source discrimination of small events, including identification of decoupled shots.

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  • Government and Political Science
  • Seismology
  • Seismic Detection and Detectors
  • Nuclear Weapons

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