Pn for the Nevada Test Site

  1. Steven R. Taylor,
  2. Howard J. Patton and
  3. Paul G. Richards
  1. L. J. Burdick,
  2. C. K. Saikia and
  3. N. F. Smith

Published Online: 18 MAR 2013

DOI: 10.1029/GM065p0197

Explosion Source Phenomenology

Explosion Source Phenomenology

How to Cite

Burdick, L. J., Saikia, C. K. and Smith, N. F. (1991) Pn for the Nevada Test Site, in Explosion Source Phenomenology (eds S. R. Taylor, H. J. Patton and P. G. Richards), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM065p0197

Author Information

  1. Woodward-Clyde Consultants, 566 EI Dorado Street, Suite 100, Pasadena, California 91101

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

A regional event discriminant has been developed and tested based on the waveform of high-frequency Pn. The data base used for testing consists of signals from explosions and earthquakes recorded on the western U.S. digital network. This net consists of the four LLNL stations MNV, KNB, ELK, and LAC; the two DWWSSN stations ALQ and JAS; and the two university-run stations PFO and PAS. It has been discovered that at most stations the waveform of Pn onset is remarkably stable and different from the corresponding waveforms from earthquakes. A forward modeling study of broad-band explosion Pn's revealed that the distinctive character of their waveform is caused by a strong pPn arrival. Depth phases from earthquakes arrive much later in the signal. It was found that a clear effective pPn arrival was present in all cases. However, for the explosions, it consistently arrives later than the predicted elastic time. For Pahute events, the amplitude of effective pP is close to the elastic predictions. For Yucca Valley, the amplitude is consistently larger, indicating the effect of a site-dependent nonlinear process in the source region. An appropriate value of t* for Pn appears to be in the range of 0.1 to 0.2 seconds. The frequency content of the explosion Pn energy indicates that it is caused by turning rays in the lid gradient rather than true head waves traveling on the crust mantle interface. The discrimination capacity of the Pn waveform was measured quantitatively by correlating the average explosion Pn trace with a data base of explosion and earthquake signals. The populations separated to a significant level down to magnitude less than 4.0. It was found that the average explosion waveform from one station could be used to discriminate data from a different station, establishing that the Pn waveform discriminant is transportable.