same volume.
The excavation of such a cavity would be fairly costly,
and its use might be limited to a single occasion because it might cave
in. To find out to what extent the seismic signal from an underground
explosion could be reduced by suitable choice of medium, manytests
would be required but most of these could be carried out at low yield.
It is likely that reduction of seismic signal is easier for low-
Unconsolidated material is found
only in the top layers of the earth and the required burial depth
increases with yield, so that it may be difficult to find such material
deep enough to successfully contain a 50-kiloton test. The digging of
underground caves large enough to give a substantial reduction of the
seismic signal from a 50-kiloton explosion will be very costly and may
in fact be impossible, especially since for mechanical stability a cave
arpa
yield shots than for high-yield ones.
4
'
!
}
t
It should be pointed out that 1 and 5 kilotons refer to the size of
the seismic signal, not to the actual yield. By proper choice of the
SECRET-“#"RES TRIOTERDATA
ESR Sy
eRe bheg ey ey
~
“ry
.
”
ne
not be distinguished from nuclear explosions and therefore will require
further investigation on the spot. If the limit is set at 5 kilotons the
number of unidentifiable earthquakes will be about 35.
ataf
The most
———
per year in the USSR which give signals of similar strength.
promising feature of seismic signals from underground explosions
distinguishing them from earthquakes is that the first pulse from
explosions always corresponds to compression while the first pulse
from an earthquake is compressive in two quadrants, while it corresponds
to dilatation in the other two. It is estimated in Appendix A that there
will be about 300 earthquakes of strength equivalent to 1 kiloton or over
which will give signals in the proposed seismic detection net which can~
wan Tren He
mae es
shot will be detected by the net of seismic stations proposed for the
USSR in that appendix. However, there are about 2500 earthquakes
oe
Se ee ee
:
7 otha?
Om,
ws
a
x
ata
+ plas
It is shown in Appendix A that the seismic wave from a 1]-kiloton
subsurface explosion in surroundings similar to those of the Rainier
en Se
Identification
WTt :
V.
<
"looks like" 1/2 kiloton, but more difficult to make a 50-kiloton explosion
e
appear like 5 kilotons.
» 4
SRRTS a i
must be smaller at great depth than near the surface. Thus it may well
be possible to reduce the signal from a 5-kiloton explosion so that it