Abstract

Amplitudes of P waves recorded by long-period seismographs for nuclear explosions in Novaya Zemlya, the Nevada Test Site, and Amchitka Island yield a new body-wave magnitude calibration function for teleseismic distances. At some distances, it differs from the Gutenberg-Richter (1956) function by as much as 0.4 magnitude units.

A comparison of short- and long-period body-wave magnitudes for the 1966 Novaya Zemlya event indicates that anelastic attenuation of P waves is greater in the upper than in the lower mantle, but, for waves with periods of 1 sec or greater, the effect of anelastic attenuation on the amplitudes is less than that of geometric spreading.

The amplitude data hint at the existence of a second-order velocity discontinuity in the lower mantle at a depth of about 2300 km.

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