Travel times and amplitudes of principal body phases recorded from gnome

Abstract

Gnome, an undergound nuclear explosion in salt near Carlsbad, New Mexico, produced seismic waves which were recorded widely throughout the United States and at a few foreign stations. The travel times of P were strongly dependent on the path of propagation, and were as much as 12 seconds earlier in the eastern United States than at equivalent distances in the western part of the United States. At the few stations more distant than 25°, P was about 2 seconds earlier than predicted by the Jeffreys-Bullen table for surface focus. Amplitudes of Pn were similarly dependent upon the path of propagation; although the measurements showed great scatter, amplitudes to the east were generally larger than those to the west. Pn travel time and amplitude anomalies suggest a systematic relationship to crustal thickness. There is evidence from the difference in the speeds and attenuation rates that Lg and P are not transmitted along analogous paths through the crust. Short period body waves were two or three times larger than expected from an explosion of the same energy in tuff at the Nevada Test Site. Surface waves, however, were relatively weak compared with explosions of similar yield in tuff.