-6- large aperture seismic arrays (LASA) in which 500 or more seismometers are located. The objective of these arrays is to discover clandestine underground nuclear explosions anywhere in the world. The quantity of seismic data recorded on both sides of the world is prodigious. The United States successfully detected the first Soviet nuclear explosion by methods of this kind in 1949. Many subsequent events in East and West have also been recorded. In a constant effort to improve detection capability, systems of instrumentation have been developed which exceed all former performance characteristics. Moreover, the continual examination of huge quantities of data by machine methods has led to reliable determinations of the location and yield of these events. These programs of nuclear detection have provided the seismologists of the world with opportunities to solve problems in seismology hitherto regarded as impossible. The net result has been an expansion in knowledge and understanding of the principles of seismology throughout the world, From this improved position have arisen further applications to other areas of seismology, e.g., exploration, earthquakes and effects of seismic disturbances, AEC SAFETY PROGRAM [DOE ARCHIVES A principal consideration of the Atomic Energy Commission is the safety of life and property from effects of underground nuclear detonations I have portrayed for you the extremely comprehensive background on which all considerations of safety are now based. The goal of safety for each ZG