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Published April 10, 1977 | Published
Journal Article Open

The effect of attenuation on gross earth models


In most recent free oscillation studies of the earth's interior the effect of absorption upon the eigenperiods of the earth has been ignored. This is equivalent to assuming that the earth is close to perfectly elastic. Since the actual earth is significantly anelastic over seismic frequencies, a frequency-dependent correction of the order of 1% must be applied to the normal mode periods in order that models based on those modes may be compared with body wave results. The eigenperiods of an earth model based on uncorrected data, model C2 (Anderson and Hart, 1976a), are adjusted for attenuation and then inverted to determine the resulting overall perturbation in the earth model. The corrected normal mode data as well as the uncorrected data can be fitted by a spherically symmetric earth model. The effect of including the attenuation term is to generally increase seismic velocities, particularly shear velocities, throughout the model. An important consequence of this change is to reduce or eliminate base line discrepancies between body wave results and normal mode results.

Additional Information

Copyright 1977 by the American Geophysical Union. (Received July 23, 1976; revised November 22, 1976; accepted December 12, 1976.) Paper number 6B0923. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Office of Scientific Research under contract F44620-72-C-0078. We thank Tom Jordan and Richard Sailor for calling our attention to two recent Soviet papers on the subject of this paper. Contribution 2788 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.

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