Near-Source Scattering of Rayleigh to P in Teleseismic Arrivals from Pahute Mesa (NTS) Shots

  1. Steven R. Taylor,
  2. Howard J. Patton and
  3. Paul G. Richards
  1. Indra N. Gupta,
  2. Thomas W. McElfresh and
  3. Robert A. Wagner

Published Online: 18 MAR 2013

DOI: 10.1029/GM065p0151

Explosion Source Phenomenology

Explosion Source Phenomenology

How to Cite

Gupta, I. N., McElfresh, T. W. and Wagner, R. A. (1991) Near-Source Scattering of Rayleigh to P in Teleseismic Arrivals from Pahute Mesa (NTS) Shots, in Explosion Source Phenomenology (eds S. R. Taylor, H. J. Patton and P. G. Richards), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM065p0151

Author Information

  1. Teledyne Geotech314 Montgomery Street, Alexandria, Virginia 22314

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875900315

Online ISBN: 9781118663820

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Keywords:

  • Underground nuclear explosions—Detection—Congresses;
  • Seismology—Congresses

Summary

Gupta et al. [1985a] proposed that near-source scattering of fundamental-mode Rayleigh-to-P (Rg[RIGHTWARDS ARROW]P) may be responsible for the large amplitude arrivals immediately following P and pP on NORSAR records of NTS shots. In this study, analyses of teleseismic data from Pahute Mesa (NTS) shots recorded at seismic arrays provide additional support in favor of the Rg[RIGHTWARDS ARROW]P scattering mechanism. Good agreement between the observed and expected spectral ratios indicates that scattering of the explosion-generated Rg, apparently due to hetero-geneities within the source region, gives rise to the large amplitude, low-frequency arrival beginning just after the pP. In accordance with theory for the generation of Rg from an explosion source, the observed spectra and amplitude of the Rg[RIGHTWARDS ARROW]P arrival, for frequencies no higher than about 2 Hz, are strongly dependent on the ratio (shot depth)/(overburden velocity). Several other investigators have suggested these secondary arrivals to be the slapdown phase associated with near surface spallation but our results favor the scattering mechanism. An understanding of these later phases can provide useful source information (including shot depth and medium velocity) and make a significant contribution to the understanding of teleseismic P arrivals from nuclear explosions.