A survey of complaints of seismic-related damage to surface structures following the Salmon underground nuclear detonation

Abstract

Following Salmon, the undergound nuclear experiment in Mississippi, numerous unexpected complaints of damage were received from residents living 15 to 40 km away. The claimed damage is mostly cracks in plaster, stucco, and masonry. Ground motion at these ranges was within the predicted safe limits, with peak surface-particle velocities roughly an order of magnitude below the 5 to 10 cm/sec previously accepted as the threshold for damage. It is shown that a 5 cm/sec damage threshold is not descriptive of this area, and revised damage criteria need to be formulated that take into consideration geology, frequency spectrum, and other factors in addition to surface particle velocity. The claimed damage is similar to that normally found in Mississippi homes where it is attributed to poor foundation soils. The triggering by Salmon of naturally occurring settlement cracks is suspected, but the physics of the process is not yet fully understood. Further complications in the survey are introduced by local sociology and psychology and public relations factors.