tbe
The region from 55 feet to 130 feet is still imp®* vious
but was apparently crushed since the drilling shows water return but
no core return. It has not yet been feasible to detect this crushed
region by sonic measurements even from inside the tunnel, so that
detection by sonic means from above the surface is at least very
difficult.
Diagnostic kixperiments
ie
lif,
Diagnostic experiments necessary for weapon development
can be easily carried out underground.
The yield can be measured
be
by shock arrival time measurements in the rock, analagous to the
fireball measurements above ground. This wae done on Rainier and
appears to be accurate to 10% even without a calibration,
The radius
of the radioactive debris or the armount of material melted might also
be used if the medium is calibrated by a shot of known yield. The
prompt diagnostics such as neutron and gamma ray measurements to
give time interval or propagation burning data, streak camera work,
etc., can be done better below than above ground since the shielding
is free and one need only drill holes as desired. Radiochemistry
has not been demonstrated to be satisfactory, since fractionation
does occur, Howevcr, the use of hollow pipes leading into reception
chambers from the cevice may give a substantial fraction of debris
unfractionated, and may lead to satisfactory radiochemical diagnostics.
Preliminary estimates indicate that a test operation can be
6
carried out more cheaply underground than on towers and balboons.
The diagnostic stations could also be underground for clandestine
tests (in fact they probably will be even if the tests are not hidden).
Keeping underground tests secret will increase the costs by preventing
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lity of proving a violation.
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the use of a single diagnostic bunker for many shots on the basis that
more than one in a given vicinity increases suspicion and the possibi-
It may mean that each shot must be ina
completely different area, but this conclusion may be modified to some
extent, because also natural earthquakes have aftershocks. In any
event, such extra costs are associated with clandestine tests generally
IV,
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7 SET perryan erden Bs PP Raa
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rather than underground tests specifically and are not likely to be more
than a few million per shot, which is not a large percentage increase.
Dependence of Seismic Signal on Yield and Medium
On the basis of observations, it is believed that the amplitude
of the earth motion from an underground explosion increases as the
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