~8- ie evacuated from the area. Such an area is extremely limited and normally not accessible by members of the public. The consideration of safety of persons thus revolves about what happens to buildings and other structures which may be set into vibration by motion of the ground nearby. We approach this problem from the beginning, namely, the source of the explosion. A definite quantity of energy concentrated within a small spherical volume is suddenly released into the crust of the earth. We take account of the total energy and partition it into fractions for which specific effects will be predicted. Within micro-seconds a predictable volume of earth materials will be heated to the point of melting and vaporization. This volume and the associated pressures are predictable for a given yield and given earth materials. Very quickly the spherical cavity expands in all directions, pressing the outgoing walls against surrounding rock. A zone of plastic deformation follows, outside of which there is a zone of cracking. energy. Each of these zones consumes large fractions of the total About 50% is deposited at the source. consumed in plastic deformation and cracking. Another fraction is Finally, the pressure hes fallen so low it can no longer push out the walls of the sphere and the remaining energy is the source of a seismic disturbance, less than 5% of the total. DOE ARCHIVE: Following the laws of scientific seismology, this spherical source radiates seismic waves in all directions. The paths of propagation can be predicted in terms of the rock properties and their distributions. In some respects this event now resembles a very small earthquake, The difference is the small size and spheroidal shape of the source as contrasted with the usual extended linear nature of an earthquake source. 2B