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Seismic Excitation of the Polar Motion, 1977-1993The mass redistribution in the earth as a result of an earthquake faulting changes the earth's inertia tensor, and hence its rotation. Using the complete formulae developed by CHAO and GROSS (1987) based on the normal mode theory, we calculated the earthquake-induced polar motion excitation for the largest 11,015 earthquakes that occurred during 1977.0-1993.6. The seismic excitations in this period are found to be two orders of magnitude below the detection threshold even with today's high precision earth rotation measurements. However, it was calculated that an earthquake of only one tenth the size of the great 1960 Chile event, if happened today, could be comfortably detected in polar motion observations. Furthermore, collectively these seismic excitations have a strong statistical tendency to nudge the pole towards approximately 140deg E, away from the actual observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field by CHAO and GROSS (1987), manifests some geodynamic behavior yet to be explored.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Chao, Benjamin Fong
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Gross, Richard S.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Han, Yan-Ben
(Academia Sinica Beijing, China)
Date Acquired
August 19, 2013
Publication Date
January 1, 1996
Publication Information
Publication: PAGEOPH
Volume: 146
Issue: 3/4
ISSN: 0033-4553
Subject Category
Distribution Limits
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