known to have been perceived by persons without benefit
of instruments has been about 100 miles.
These few persons
were situated under conditions favorable to the amplification
of the ground motions. No structural damage from ground
motion has been experienced beyond about six miles from the
site of the nuclear detonations.
Evaluation
Records of ground motion are now available for many underground nuclear explosions. Analyses of data and application
of geophysical principles are resulting in a steady improvement
in methods of prediction of ground motions for planned events.
Since ground motions from underground nuclear explosions
are different in some respects from those from an earthquake
and there is a need to predict marginal damage to structures
for such explosions a new approach is required. The analytical procedures for structural response generally are valid
and can be applied. Additional direct test information is
required and is being acquired by the AEC.
Until more data
are developed, conservative estimates of the effects may be
made by comparison with damage which might be expected
from the same amplitude of ground motion in an earthquake.
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