Inner core transition zone and anomalous PKP(DF) waveforms from polar paths

Xiaodong Song, Xiaoxia Xu

Research output: Contribution to journalArticlepeer-review


Short-period PKP(DF) waves (which travel through the inner core) from polar paths (nearly NS) were observed to have small amplitudes and complex waveforms but the cause has been a mystery. Here we examine both short-period and broadband PKP record sections from a single earthquake in South Sandwich Islands (SSI). The data from polar paths show clear evidence for an inner core triplication. Our waveform modeling suggests a 250-km thick isotropic upper inner core (UIC) overlying an anisotropic lower inner core (LIC) with about 8% anisotropy. The synthetics match the observed waveforms and amplitudes well with a normal value of inner core attenuation. We propose that such a UIC/LIC transition zone structure may be the cause of anomalous DF waveforms along polar paths. The inferred level of anisotropy in the LIC, 2-3 times previous estimates, has important implications for understanding physical properties of the inner core and sources of inner core anisotropy.

Original languageEnglish (US)
Pages (from-to)1-1-1-4
JournalGeophysical Research Letters
Issue number4
StatePublished - Feb 15 2002

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)


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