pure and applied geophysics

, Volume 146, Issue 3–4, pp 407–419

Seismic excitation of the polar motion, 1977–1993

  • Benjamin Fong Chao
  • Richard S. Gross
  • Yan-Ben Han


The 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 byChao andGross (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 ∼140°E, away from the actually observed polar drift direction. This non-random behavior, similarly found in other earthquake-induced changes in earth rotation and low-degree gravitational field byChao andGross (1987), manifests some geodynamic behavior yet to be explored.

Key words

Earthquake polar motion earth rotation 


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Copyright information

© Birkhäuser Verlag 1996

Authors and Affiliations

  • Benjamin Fong Chao
    • 1
  • Richard S. Gross
    • 2
  • Yan-Ben Han
    • 3
  1. 1.Geodynamics BranchNASA Goddard Space Flight CenterGreenbeltUSA
  2. 2.Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadenaUSA
  3. 3.Beijing Astronomical ObservatoryChinese Academy of SciencesBeijingChina

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