Calculation of first-zonePwave amplitudes for Salmon Event and for decoupled sources

Abstract

Theoretical calculations of the first half-cycle amplitudes of the P wave at 250 to 1000 km are made from source functions representing several types of nuclear explosions in salt. Specifically, they are (1) Gnome scaled to 5 kt; (2) Salmon; (3) theoretical 25 kt detonated in a cavity built to fully decouple a 5-kt explosion; and (4) theoretical 5 kt also detonated in a 5-kt cavity. The calculations consist of a series of convolutions of the source functions plus the attenuation operators plus the instrument response. Amplitude factors are calculated using Zvolinskii's near-front approximation for various assumed crustal models. Experimental amplitudes from Salmon fall below the amplitude curve for the scaled Gnome source. They are consistent with amplitudes for the Salmon source; therefore, head-wave propagation along the M discontinuity may occur in the eastern United States. This is not conclusive, however, since body-wave calculations might give amplitudes of equal consistency. Amplitudes calculated for the fully decoupled 5-kt source show a decoupling of 200. Those from the overdriven cavity source indicate that a partial decoupling of 80 can be gained by overdriving a cavity by a factor of 5. INTRODUTION T•E SOURCEThere has been some contention that no true head wave from the M discontinuity would be seen as a first arrival from the Salmon event.This argument was based on the apparent differences in the earth's crust in the eastern continental United States from those in the west.

Nuclear Decoupling, Full and Partial

“…Comparing the 4000-m • value from Salmon with the 21-m • value from the 5-kt decoupled cavity, we have a salt-to-salt decoupling ratio of about 200. This is consistent with decoupling calculations and Salmon measurements at the 500-km range [Springer, 1965].…”

Symposium on Engineering With Nuclear Explosives, Las Vegas, Nevada, January 14--16, 1970. Proceedings.

“…Removal efficiencies of 80 to 100 per cent were obtained at hydraulic detention times of one-half hour to two hours with all matrix media except the three-inch gravel, which attained 58 to 76 per cent removal at three to aix-hour detention times [47]. Apparently the void spaces in the three-inch gravel were too large to provide good biological solids retention.…”

“…Reduction of the device yield would reduce the initial concentrations of radioactivity correspondingly. Costs quoted in Table V-b are based on [9,12,46,47].…”

“…A comprehensive experimental-theoretical study of an underground nuclear event from explosive detonation to distant seismic signal has been published for only one experiment, Salmon. 45,46,47 This work concerned only the first P-wave arrival in the first zone, the head wave that is critically refracted at the Mohorovicic discontinuity. Other experimental-theoretical studies beginning with the measured reduced displacement potential (instead of the explosive detonation) and ending with the head wave arrival have been made.°>28 Toksoz et al4° used R-wave measurements from several nuclear explosions together with an appropriate layered geological model to calculate a seismic source function (equivalent to a reduced displacement potential) for the explosion.…”

Seismic monitoring: a unified system for research and verifications

“…During the last two decades considerable effort has been devoted to research projects necessary to improve techniques for monitoring underground nuclear explosions. These investigations have included development of seismic scaling laws [Utter et al, 1959;Romney, 1959;Weston, I960;Werthand Herbst, 1963;Mueller and Murphy, 1971;Carpenter, 1967;Murphy, 1977;Peppin\ 1977, studies on seismic coupling [IVerth eta)., 1962;lMtter et al, 1961;Springer. 1966aSpringer.…”