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Published December 1978 | Published
Journal Article Open

Attenuation measurements of split normal modes for the 1960 Chilean and 1964 Alaskan earthquakes


Measurements of attenuation for the Earth's longest period modes can be significantly biased by the effects of frequency splitting. Using our previously developed methods of time domain synthesis of split normal modes, we measure Q without such a bias. We also conduct numerical experiments to confirm the errors in Q measurements which result from neglecting the effects of splitting. In contrast to frequency domain this time domain technique allows us to reject data below the ambient noise level for each mode. The Q's of the longest period spheroidal (_0S_(2–0)S_5) and torsional (_0T_(3–0)T_4) modes are determined using long (500 hr) records from the Chilean and Alaskan earthquakes.

Additional Information

© 1978 Seismological Society of America. Manuscript received May 26, 1978. We thank Yoshio Fukao, Hiroo Kanamori, Stewart Smith, and Ralph Wiggins for advice and assistance. Richard Sailor provided us with translations of the papers by Akopyan et al. Seth Stein was supported by a fellowship from the Fannie and John Hertz Foundation. This research was also supported by National Science Foundation Grant EAR78-03653 at Stanford and National Science Foundation Grants EAR76-14262 and 7803653 at Stanford and by National Science Foundation Grant EAR77-14675 at Caltech.

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