COMPARING UNITED-STATES AND RUSSIAN EXPERIENCE WITH CAVITY DECOUPLINGIN SALT

Recently released Russian data on two underground nuclear explosions i n an Azgir salt dome allow comparison for the first time with similar U. S. explosions. In both cases, highly tamped explosions were employe d to form cavities and, after a period of several years, much smaller explosions were then carried out in these same cavities. The seismic d ecoupling factor obtained from the Russian tests appears to be a facto r of 4 less than is predicted, based on the U. S. experience. However, the Russian data are found to be entirely consistent with smaller sca le U. S. experiments with chemical explosives. These results can be ex plained by the extent of damage in the immediate vicinity of the cavit y walls, but it remains unclear why the damage should exist at the Rus sian site, and not at the U. S.