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APPENDIX c. * 
Gravity waves in the sea caused explosions 
If a emall charge, say a few ounces, is exploded just above or 
below a water surface, an impressive wave system is generated. The 
scaling laws from small to large charges, however, are such that large 
charges generate disappointingly small wave systems, particularly if the 
charge is exploded above the water surface. 
The waves caused by an explosion below the surface is supposed to 
result mainly from the creation of a cavity which breaks near its 
maximum. The largest cavity is caused when the depth of the charge is 
about 70-80% of the maximum bubble radius, a result which allows the 
optimum depth to be calculated. The wave height at distances proportional 
to the linear dimensions of the bubble (or cavity) are directly 
proportional to the linear dimensions of the cavity. Since the bubble 
is created against a pressure which is the sum of atmospheric pressure 
and a head of water equal to the depth, the size of the cavity increases 
less rapidly with charge weight than does the linear dimensions of the 
chargee 
When the charge is exploded a few charge radii above the water 
surface, the wave system is generated by the impulse given to the water 
surface. In this case, the scaling law is that the wave height at 
distances proportional to the linear dimensions of the charge is 
proportional only to the sixth root of the charge weight. Comparatively 
enormous charges (eege the atomic bomb) cause waves only a few inches high 
at a distance of 1,000 yards. 
If the depth of water is only of the order of a few charge radii, 
the waves near the centre are comparable in height with the depth of water, 
and therefore probably break. The theory of small wave heights is no 
longer applicable, and the waves must be considered more analogous to a 
tidal bore. 
Broadly speaking, gravity waves caused by explosions are of little 
operational interest, but there are two possible exceptions (a) where the 
e is enormous (several thousands of tons, in relatively shallow 
water), (b) where multiple charge arrays, giving a “beam", are employed. 
