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Published June 1977 | Published
Journal Article Open

Split free oscillation amplitudes for the 1960 Chilean and 1964 Alaskan earthquakes


Splitting of the Earth's normal modes was observed for both the 1960 Chilean and 1964 Alaskan earthquakes. The strong peaks in the observed spectrum of each split multiplet correspond to singlets with much higher amplitudes than the others. Using theoretical results we have derived elsewhere (Stein and Geller, 1977a), we are able to predict this pattern. We show that the source mechanisms inferred for these earthquakes from surface waves are consistent with the observed pattern of relative spectral amplitudes of the split modes. However other mechanisms, such as a slow isotropic volume change, are also consistent with the split-mode amplitudes and are excluded only by additional data.

Additional Information

Copyright © 1977, by the Seismological Society of America. Manuscript received December 7, 1976. We thank Hiroo Kanamori for his advice and assistance, and for allowing us to use his results prior to publication. Seth Stein was supported by a fellowship from the Fannie and John Hertz Foundation and this research was supported by the National Science Foundation under Grants EAR74-22489 and EAR76-14262.

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