C. WEATHER As a crude comparison, the 10.4 million tons TNT equivalent . Background Information Interest in the possible effects of nuclear detonations on the weatherfall into two classes; one, direct effects because of the energy released, and two, triggering effects. The latter effects might be (a) a catalytic effect from the particles thrown into the atmosphere (something akin to cloud seeding with silver iodide crystals), (b) a change in the electrical conductivity of the air since radioactive debris contains chargedparticles, and (c) a reduction of solar energy received on earth owing to the quantity of dust thrown into the atmosphere. The Data The conclusions of many studies and experiments of these possible effects are best presented in reference:* 1. “... The energy of even a thermonuclear ex- plosion is small when compared to most large-scale weather processes. Moreover, it is known that much of this energy is expended in waysthat cannotdirectly affect the atmosphere. Even thefraction of the energy which is directly added to the atmosphere is added in a rather inefficient manner from the standpoint of affecting the weather. Meteorologists and others acquainted with the problem are readily willing to dismiss the possibility that the energy released by the explosions can have any important direct effect on the weather processes...” 2. “.,.The debris which has been thrown up into the atmosphere by past detonations was found to be ineffective as a cloud-seeding agent...” 3. “... The amount of ionization produced by the radioactive material is insignificant in affecting general ; atmospheric conditions . . .” 4. “.., Dust thrown into the air by past volcano eruptions decreased the direct solar radiation received at the ground by as much as 10-20 percent. The contamination of the atmosphere by past nuclear tests has not produced any measurable decrease in the amount of direct sunlight received at the earth’s surface. plosions There is a possibility that a series of ex- designed for the maximum efficiency in throwing debris into the upper atmosphere might significantly affect the radiation received at the ground...” The volume of material ejected by Krakatoa volcanic eruption in 1883 was approximately 13 cubic miles with an estimated reone-third of the volume being spread worldwide.” This sulted in a diminution of the amount of sunlight received on the ground. nuclear detonation on October 31, 1952 on the island of Elugelab in the Pacific left a crater of about one mile in diameter and 170 feet deep at its apex. Assuming conservatively that the crater was a right angle cone and that all of the debris was thrown into the atmosphere, i.e., none of the depression was caused by compression, it is estimated that about 15,000 million tons TNT equivalent of surface detonations would be required to eject an amountof dust into the atmosphere equivalent of Krakatoa. Following large nuclear detonations in the Pacific minor and temporary weather changes have been observed, such as local cloud formation sometimes with local precipitation, where the moisture conditions in the atmosphere are most favorable for this effect. Evaluation The most inclusive evaluative statements made are found in references 31 and 2. “| ..No statistically significant changes in the weather during the first ten years of the atomic age have been found, yet careful physical analysis of the effects of nuclear explosions on the atmosphere must be madeif we are to obtain a definite evaluation of this problem. Although it is not possible to prove that nuclear explosions have or have not influenced the weather, it is believed that such an effect is un- likely . . .” (1956). “.. although there has been much speculation about the influence of atomic testing on weather, there still appears to be no additional evidence suggesting a cause andeffect relationship . . .” (1960). D. GROUND MOTIONS — EARTHQUAKES Background Information A wide variety of factors determine both the ground motions and structural responses from nuclear detonations,i.e., energy yields of the detonations, distance from ground zero, depth of the shot and depth of measurement, and the nature of the ground (hard rock, etc.). “Competent” rock such as granite couples and transmits more energy into seismic ground waves than does alluvium—a noncohesive sedimentary deposit. Although ground waves will be more rapidly absorbed in al- luvium, it is possible for waves to travel great distances along the surface with relatively large amplitudes (amountof motion) if the alluvium is very thick. However, these surface waves die out rapidly with the depth into the ground. Because of the 27