Skip to main content
SpringerLink
Log in

Attenuation in the uppermost inner core from PKP recordings at African seismological stations

  • Published:
Studia Geophysica et Geodaetica Aims and scope Submit manuscript

Abstract

The attenuation factor QP at the top of the inner core is evaluated by using the amplitude spectral ratio of PKPdf and PKPbc phases observed at African stations (BGCA mostly), from strong deep earthquakes in the Pacific Ocean area. The maximum depth of penetration of the PKPdf phase into the inner core (IC) is roughly 377 km, and the sampled region of IC is centered beneath the Southern Indian Ocean. The derived mean value of QP is 249 ± 31 (95% confidence level) in the frequency range 0.2–2 Hz, where no frequency dependence of attenuation has been reliably observed. By using Student’s t-test, we show that the value is statistically significantly different (with a probability greater than 95%) from other mean values of Q derived by using the same method, for both the western (180 °W to 40 °E) and eastern (40 °E to 180 °E) hemispheres of the IC. The decrease of Q with the radius of the turning point (denoted by rTP), according to QP = 840 − 0.62 rTP, has a moderate statistical support (the R-squared value is 38%). A slightly increase of Q as a function of the angle of the PKPdf path within the inner core with respect to the Earth’s spin axis is observed, in agreement with various investigations performed in the time domain. However, the value of the anisotropy, if any, is suggested to be around 3%.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  • Bhattacharyya J., Shearer P. and Master G., 1993. Inner core attenuation from short period PKP(BC) versus PKP(DF) waveforms. Geophys J. Int., 114, 1–11.

    Article  Google Scholar 

  • Bowers D., McCormack D.A. and Sharrock D.S., 2000. Observations of PKP(DF) and PKP(BC) across the United Kingdom: implications for studies of attenuation in the Earth’s core. Geophys J. Int., 140, 374–384.

    Article  Google Scholar 

  • Cao A. and Romanowicz B., 2004. Hemispherical transition of seismic attenuation at the top of the Earth’s inner core. Earth Planet. Sci.Lett., 228, 3–4.

    Article  Google Scholar 

  • Cormier V.F., 1981. Short-period PKP phases and the anelastic mechanism of the inner core. Phys. Earth Planet. Inter., 24, 291–301.

    Article  Google Scholar 

  • Cormier V.F. and Li X., 2002. Frequency dependent attenuation in the inner core: part II. A scattering and fabric interpretation. J. Geophys. Res., 107, doi:10.1029/2002JB001796.

    Google Scholar 

  • Cormier V.F. and Stroujkova A., 2005. Waveform search for the innermost inner core. Earth Planet. Sci. Lett., 236, 96–105.

    Article  Google Scholar 

  • Cummins P. and Johnson L.R., 1988. Short-period body wave constraints on properties of the Earth’s inner core boundary. J. Geophys. Res., 93, 9058–9074.

    Article  Google Scholar 

  • Doornbos D.J., 1974. The anelasticity of the inner core. Geophys. J. R. Astron. Soc., 38, 397–415.

    Google Scholar 

  • Doornbos D.J., 1983. Observable effects of the seismic absorption band in the Earth. Geophys. J. R. Astron. Soc., 75, 693–711.

    Google Scholar 

  • Draper N.R. and Smith H., 1966. Applied Regression Analysis. John Wiley & Sons, New York, 407 pp.

    Google Scholar 

  • Garcia R., 2002. Constraints on upper inner core structure from waveform inversion of core phases. Geophys J. Int., 150, 651–664.

    Article  Google Scholar 

  • Helffrich G., Kaneshima S. and Kendall J.-M., 2002. A local, crossing-path study of attenuation and anisotropy of the inner core. Geophys. Res. Lett., 29, 1568–1572.

    Article  Google Scholar 

  • Helffrich G. and Kaneshima S., 2004. Seismological constraints on core composition from Fe-O-S liquid immiscibility. Science, 306, 2239–2242.

    Article  Google Scholar 

  • Ishii M. and Dziewonski A.M., 2002. The innermost inner core of the Earth: evidence for a change in anisotropic behavior at ∼300-km radius. PNAS, 99, 14026–14030.

    Google Scholar 

  • Ivan M. and Popa M., 2004. Attenuation in the uppermost inner core from PKP observed at some Romanian stations. J. Balkan Geophys. Soc., 7, 23–29.

    Google Scholar 

  • Ivan M., Marza V., de Farias Caixeta D. and de Melo Arraes T., 2006. Uppermost inner core attenuation from PKP data observed at some South American seismological stations. Geophys J. Int., 164, 441–448.

    Article  Google Scholar 

  • Kennett B.L.N., Engdahl E.R. and Buland R., 1995. Constraints on seismic velocities in the Earth from travel times. Geophys J. Int., 122, 108–124.

    Article  Google Scholar 

  • Krasnoshchekov D.N., Kaazik P.B. and Ovtchinnikov V.M., 2005. Seismological evidence for mosaic structure of the surface of the Earth’s inner core. Nature, 435, 483–487.

    Article  Google Scholar 

  • Li X. and Cormier V.F., 2002. Frequency dependent attenuation in the inner core: part I. A viscoelastic interpretation. J. Geophys. Res., 107, doi:10.1029/2002JB001795.

    Google Scholar 

  • Loper D.E. and Roberts P.H., 1981. A study of conditions at the inner core boundary of the earth. Phys. Earth Planet. Inter., 24, 302–307.

    Article  Google Scholar 

  • Masters G. and Gilbert F., 1981. Structure of the inner core inferred from observations of its spheroidal shear modes. Geophys. Res. Lett., 8, 569–571.

    Google Scholar 

  • Morelli A., Dziewonski A.M. and Woodhouse J.H., 1986. Anisotropy of the inner core inferred from PKIKP travel times. Geophys. Res. Lett., 13, 1545–1548.

    Google Scholar 

  • Niazi M. and Johnson L.R., 1992. Q in the inner core. Phys. Earth Planet. Inter., 74, 55–62.

    Article  Google Scholar 

  • Niu F. and Wen L., 2001. Hemispherical variations in seismic velocity at the top of the Earth’s inner core. Nature, 410, 1081–1084.

    Article  Google Scholar 

  • Poupinet G., Pillet R. and Souriau A., 1983. Possible heterogeneity in the Earth’s core deduced from PKIKP travel times. Nature, 305, 204–206.

    Article  Google Scholar 

  • Souriau A. and Souriau M., 1989. Ellipticity and density at the inner core boundary from subcritical PKiKP and PcP data. Geophys J. Int., 98, 39–54.

    Article  Google Scholar 

  • Souriau A. and Roudil P., 1995. Attenuation in the uppermost inner core from broad-band GEOSCOPE PKP data. Geophys J. Int., 123, 572–587.

    Article  Google Scholar 

  • Souriau A. and Romanowicz B., 1996. Anisotropy in inner core attenuation: a new type of data to constrain the nature of the solid core. Geophys. Res. Lett., 23, 1–4.

    Article  Google Scholar 

  • Souriau A. and Romanowicz B., 1997. Anisotropy in inner core: relation between P-velocity and attenuation. Phys. Earth Planet. Inter., 101, 33–47.

    Article  Google Scholar 

  • Stearn S.D., 1975. Digital Signal Analysis. Hayden Book Co., Inc., New Jersey, USA.

    Google Scholar 

  • Stevenson D.J., 1987. Limits on lateral density and velocity variations in the Earth’s outer core. Geophys. J. R.. Astron. Soc., 88, 311–319.

    Google Scholar 

  • Stroujkova A. and Cormier V.F., 2004. Regional variations in the uppermost 100 km of the Earth’s inner core. J. Geophys. Res., 109, doi:10.1029/2004JB002976.

    Google Scholar 

  • Tromp J., 1993. Support for anisotropy of the Earth’s inner core from free oscillations. Nature, 366, 678–681.

    Article  Google Scholar 

  • Tromp J., 1995. Normal-mode splitting observations from the Great 1994 Bolivia and Kuril Islands earthquakes: constraints on the structure of the mantle and inner core. GSA Today, 5, 137–151.

    Google Scholar 

  • Tseng T.L., Huang B.S. and Chin B.H., 2001. Depth-dependent attenuation in the uppermost inner core from the Taiwan short period seismic array PKP data. Geophys. Res. Lett., 28, 459–462.

    Article  Google Scholar 

  • Wessel P. and Smith W.H.F., 1996. A global, self-consistent, hierarchical, high-resolution shoreline database. J. Geophys. Res., 101, 8741–8743.

    Article  Google Scholar 

  • Widmer R., Masters G. and Gilbert G., 1992. Observably split multiplets-data analysis and interpretation in terms of large-scale aspherical structure. Geophys J. Int., 111, 559–576.

    Article  Google Scholar 

  • Yu W. and Wen L., 2006. Inner core attenuation anisotropy. Earth Planet. Sci. Lett., 245, 581–594.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Dept. of Geophysics, University of Bucharest, 6 Traian Vuia Str., 70138, Bucharest o.p.37, Romania

    M. Ivan

  2. School of Ocean and Earth Sciences, Tongji University, 1239 Siping Rd., 200092, Shanghai, China

    M. Ivan

  3. Faculty of Sciences, University of Bangui, PO Box 908, Bangui, Central African Republic

    G. R. Moloto-A-Kenguemba

Authors
  1. M. Ivan
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. G. R. Moloto-A-Kenguemba
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Ivan, M., Moloto-A-Kenguemba, G.R. Attenuation in the uppermost inner core from PKP recordings at African seismological stations. Stud Geophys Geod 51, 221–230 (2007). https://doi.org/10.1007/s11200-007-0011-x

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11200-007-0011-x

Key words

Search

Navigation