P sub n from the Nevada Test Site
Abstract
A regional event discriminant is being developed and tested based on the waveform of high frequency P sub n. The data base being used in the development consists of signals from explosions and earthquakes recorded on the western U.S. digital network. It has been discovered that at most stations the waveform of P sub n onset is remarkably stable and different from the corresponding waveforms from earthquakes. A forward modeling study of broad band explosion P sub n's revealed that the distinctive character of their waveform is caused by a strong p P sub n arrival. Depth phases from earthquakes arrive much later in the signal. It was found that a clear effective p P sub n arrival was present in all cases. However, 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, it is consistently larger indicating the effect of a site dependent nonlinear process in the source region. An appropriate value of t* for P sub n appears to be in the range of 0.1 to 0.2 seconds. The frequency content of the explosion P sub n 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 P sub n waveform was measured quantitatively by correlating the average explosion P sub n trace with a data base of explosion and earthquake signals. Keywords: Synthetic seismograms, Nuclear explosion testing, Underground explosions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 15, 1988
- Accession Number
- ADA208276
Entities
People
- C. K. Saikia
- L. J. Burdick
- N. F. Smith