Teleseismic short-period amplitudes: Source and receiver variations

Abstract

Short-period P-wave amplitude data from nuclear explosions in the Soviet Union recorded by WWSSN stations in the United States are presented. Thirty-four events in five test sites are analyzed. The consistency and similarity of the initial P waveforms allow a stable amplitude measure. A well-defined amplitude pattern is obtained for each source region. The test sites at northern and southern Novaya Zemlya show a relative amplitude trend of a factor of 3 across the United States in their respective amplitude patterns. This is in contrast to two sites at Semipalatinsk which are in good relative agreement. A pattern of lateral variation of amplitude in the United States is obtained for a northern azimuth of approach. Stations situated on sediments are corrected for amplification effects. In contrast to previous studies, stations in the Western United States do not have systematically lower amplitudes than Eastern United States stations. Lowest amplitudes are found in Golden, Colorado (GOL) and Albuquerque, New Mexico (ALQ), a factor of 4 lower than high amplitude stations. Preliminary amplitude data are presented from earthquakes in the Kuriles and South America. Events are chosen for consistency of waveforms across the United States to minimize earthquake source and directivity effects. These earthquake data indicate that amplitude variations in the United States are azimuthally dependent.

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