SECTION II. - OTHER ASPECTS
A.
Blast - Direct and Reflected
Background Information-
Direct blast waves that are potentially damaging are confined to
the immediate testing site areas.
ditions, however,blast waves
Under certain meteorological con-
may be refracted (bent) from an upper
atmospheric level back to the earth and thus create relatively high blast
pressures.
One level at which this may happen is between 25,000 and 50,000
feet altitude where winds may cause a focusing effect at some 20-50
miles from the point of detonation.
In turn, the blast wave may be
repeatedly reflected from the ground and bent back from the atmosphere
creating a series of regular spaced points of focus at the earth's surface with intervening "silent" spaces.
Such an effect has resulted in
minor structural damage, such as breaking of windows, 75-100 miles
from the point of detonation at the Nevada Test Site2!.,
A similar effect is obtained when blast waves are bent from a layer
of relatively warm air, called the ozonosphere, at a height of 20 to 30
miles.
The point of first return to the earth is in this case 70-150
miles from the burst.
There may be a return of sound waves from an altitude above 60 miles
(ionosphere).
Most of this blast energy is absorbed, however, resulting
in no recorded structural damage but in some cases audible sharp cracks
and pops.
27.