Temporal Changes of the Inner Core From Globally Distributed Repeating Earthquakes

Yi Yang, Xiaodong Song

Research output: Contribution to journalArticlepeer-review


Time-dependent travel times of seismic waves traversing the inner core from repeating earthquakes provided compelling evidence for an inner core differential motion. Here we conducted a systematic search for strong repeating earthquakes in the last three decades to examine the global pattern of temporal changes of the inner core. We performed extensive analyses on the quality of the repeating earthquakes and quantified the error (σic) of travel time measurements from all possible sources except the inner core temporal changes. We set 2σic as a threshold for judging whether an inner core temporal change is significant. No significant temporal changes were found in most parts of the inner core, but large temporal changes (over 3σic) were observed beneath four regions in Northern Hemisphere (North Atlantic, Northeast Pacific, Russian Far East/Sea of Okhotsk, and Europe/North Africa), besides the well-known Central America anomaly in previous studies. Most large temporal changes were associated with time lapses of over 6 years and smaller distances, possibly resulting from the rotation shifting the laterally varying top 300 km of the inner core. A new path sampling North Atlantic suggested a small-scale and steep lateral velocity gradient of the inner core and a slow eastward inner core rotation of 0.051°/year. Small-scale lateral variations may reconcile large difference in the estimates of the inner core rotation rate. We also observed enigmatic very large abrupt temporal changes (as short as 44 days), which may be related to disturbances caused by the great Sumatra earthquakes.

Original languageEnglish (US)
Article numbere2019JB018652
JournalJournal of Geophysical Research: Solid Earth
Issue number3
StatePublished - Mar 1 2020


  • PKP
  • cross correlation
  • inner core
  • inner core rotation
  • repeating earthquakes
  • temporal changes

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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