abstract

Seismic waves resulting from a low yield nuclear detonation 1200 feet deep in a salt bed near Carlsbad, New Mexico were measured by strong-motion seismographs operated by the Coast and Geodetic Survey on the surface in the distance range from 0.5 to 8.8 miles and underground in a potash mine 8.7 to 11.2 miles distant. In addition, many temporary and permanent seismographs were operated by the Coast and Geodetic Survey and other organizations on a continentwide and a world-wide basis. Ground particle accelerations exceeded those from the Logan shot, a like detonation in tuff, by a factor of about 4, and accelerations underground in the salt bed were about half those on the nearby surface. There was no evidence of damaging accelerations in nearby commercial operations or dwellings. Nearby transient ground particle displacements were about the same as those from the logan shot, except that the frequencies were higher. Attenuation with distance across the plains to the east was relatively low as compared with similar effects in the mountain and plateau area toward the west. Upper mantle velocities likewise were higher toward the east, 8.3 to 8.4 km/sec, as compared with 7.8 to 8.1 km/sec toward the north, west, and northwest. The estimated magnitude of the gnome shot was from 4.5 to 5.0, depending on the choice of data.

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