seismic waves generated by nuclear detonations and chemical high explosives result in less damaging effects than would be predicted for the same peak acceleration from an earthquake. Part of this difference may lie in the fact that ground motions from earthquakes persist for a longer period of time for each shock. repeated shocks in most cases. Also, they are Thus, structures are subjected to more damaging effects because of the number of shocks and greater duration of each shock than would be the case for the same peak acceleration experienced as a result of ground motion from an underground nuclear explosion. Since nuclear detonations produce ground motions, it has been speculated that they may "trigger" a natural earthquake. It is not possible to have a natural earthquake, however, without prior storage of strain energy -- a process that occurs over a period of years. It would be necessary to conduct an explosion several miles deep in an earthquake susceptible area to be near a zone where the stress might be great enough for an incipient quake to be triggered.*>The response of structures to earthquakes has been the subject of study for many years and satisfactory procedures have been developed for design of structures to withstand the effects of earthquakes. However, in these cases the interest is in significant structural damage, rather than plaster cracking or other minor effects. In the case of underground nuclear explosions the site is selected with safety in mind so that structures outside the test area will ordinarily be subjected to ground motions of small amplitude. The possibility that light damage may result, therefore, must be considered.