Seismic Waves from high yield Atmospheric Explosions

Abstract

High yield test nuclear explosions in the atmosphere carried out in 1962 by the U.S.S.R. over Novaya Zemlya were well recorded by the seismographs at Delhi.  The paper presents a study of these records.  Long period Rayleigh waves were the most prominent and could be detected for most of the explosions was about 20 megatons or more.  Aprominent wave recorded on most of the days has been shown to be the Sa (Caloi) wave and has been discussed at some length.

M2-waves in the range of periods 8-15 seconds could be clearly detected.  The records also show the presence of longer period M2 waves, which have been analysed.  Dispersion of these M2 wave as also of Rayleigh waves has been studies and it is estimated that the thickness of the average continental crust along the path (Novaya Zemlya-Delhi) is 45 km whereas that under the mountain range across the path is 55-60km.

The pressure wave traveling with the speed of sound was well recorded on a number of days.  These waves show clear normal dispersion.  Results derived from the records of the vertical component seismograph compare well with earlier experimental and theoretical results.  The response of the horizontal component seismographs to these waves appears to be due to ground tilt caused by the propagation of the pressure wave.