I. The Detectability of High Frequency Energy at Teleseismic and Regional Distances. II. Studies of Radiation from High-Explosive and Nuclear Cratering Events.
Abstract
A survey of the literature on short-period seismic studies shows that seismic waves of high frequency in the 3-10 Hz range, can be observed regularly at both regional and teleseismic distances. These observations show that the low Q values proposed for the long-period seismic waves cannot be valid in the short-period band. The data indicate that, in the mantle, Q increases with frequency and may be as much as five times higher at 5-10 Hz than in the long-period band. Even with the most conservative assumptions, the level of high frequency amplitudes in the teleseismic P waves exceeds that predicted with a constant t*p = 1 sec by a factor of at least 100,000 at and beyond 5 Hz. The apparent Q beta of the lithosphere, which may be largely due to scattering by the small scale inhomogeneities in the crust, also shows an increase with frequency by as much as a factor of four within the 1-10 Hz band. This parameter controls the attenuation and the detectability of seismic waves at regional distances such as Pn, Pg, Sn and Lg. These results indicate that deriving source diagnostics for explosions and earthquakes at both teleseismic and regional distances is possible utilizing high frequencies, and methods to do this must be developed further. A survey of existing data from cratering explosions reveals that there is no hard-rock transverse component digital data. The best all-around data available is that taken in Yucca Lake by Lawrence Livermore Laboratory in 1973-1974. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 04, 1981
- Accession Number
- ADA111855
Entities
People
- R. R. Blandford
- Zoltan A. Der