On the importance of changes in the gravity field on seismic recording at ultralong periods.
The effect of changes in gravity induced by the Earth's deformation on seismic recording at ultralong periods is studied quantitatively for the low-order spheroidal modes of the Earth. Because this effect can either enhance or reduce the recorded amplitude of a mode, depending on its geometry, it may become nontrivial at the longest free-oscillation periods, and contribute to relative deviations of up to 17%.
Okal
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Department of Geology and Geophysics, Yale University, Box 6666, New Haven, Connecticut 06511.