Detection of PKJKP at intermediate periods by progressive multi-channel correlation

Emile A. Okal; Yves Cansi

doi:10.1016/S0012-821X(98)00210-6

Detection of PKJKP at intermediate periods by progressive multi-channel correlation

Emile A. Okal^*, Yves Cansi

^*Corresponding author for this work

Earth and Planetary Sciences

Research output: Contribution to journal › Article › peer-review

37 Scopus citations

Abstract

We have identified the seismic phase PKJKP, traveling through the inner core of the Earth as a shear wave, in intermediate-period (2-10 s) records of the deep 1996 Flores Sea earthquake at eight stations of the French seismic network. This constitutes direct evidence of the solidity of the inner core which, while generally recognized, was until now only inferred from indirect evidence. The arrival times on stacked seismograms require a shear-wave velocity at the top of the inner core β(ICB) = 3.65 km/s in agreement with values suggested from normal mode observations. Julian et al.'s 1972 observation of a lower velocity (2.95 km/s) is easily reconciled with our result if interpreted as the surface reflection pPKJKP. The high Poisson ratio (v = 0.44) can be reconciled with a normal crystalline structure without invoking partial melting on account of the overwhelming pressure at the center of the Earth.

Original language	English (US)
Pages (from-to)	23-30
Number of pages	8
Journal	Earth and Planetary Science Letters
Volume	164
Issue number	1-2
DOIs	https://doi.org/10.1016/S0012-821X(98)00210-6
State	Published - Dec 15 1998

Keywords

Earthquakes
Inner core
PKP-waves
S-waves

ASJC Scopus subject areas

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

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title = "Detection of PKJKP at intermediate periods by progressive multi-channel correlation",

abstract = "We have identified the seismic phase PKJKP, traveling through the inner core of the Earth as a shear wave, in intermediate-period (2-10 s) records of the deep 1996 Flores Sea earthquake at eight stations of the French seismic network. This constitutes direct evidence of the solidity of the inner core which, while generally recognized, was until now only inferred from indirect evidence. The arrival times on stacked seismograms require a shear-wave velocity at the top of the inner core β(ICB) = 3.65 km/s in agreement with values suggested from normal mode observations. Julian et al.'s 1972 observation of a lower velocity (2.95 km/s) is easily reconciled with our result if interpreted as the surface reflection pPKJKP. The high Poisson ratio (v = 0.44) can be reconciled with a normal crystalline structure without invoking partial melting on account of the overwhelming pressure at the center of the Earth.",

keywords = "Earthquakes, Inner core, PKP-waves, S-waves",

author = "Okal, {Emile A.} and Yves Cansi",

note = "Funding Information: We thank Commissariat {\`a} l'Energie Atomique for support, Yann Klinger and James Schwartz for help in previous but unsuccessful attempts to detect PKJKP, and Jeannot Trampert and Hanneke Paulssen for discussion and friendly competition. Discussion on Poisson ratios with Jean-Paul Poirier is also acknowledged. We believe it is a particularly fitting tribute to the memory of Inge Lehmann that most of this paper was written on an SAS plane during a flight between Copenhagen and Chicago. The paper was substantially improved by three careful reviews. This research was performed while EAO enjoyed the support of the National Science Foundation. [AC] Copyright: Copyright 2011 Elsevier B.V., All rights reserved.",

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doi = "10.1016/S0012-821X(98)00210-6",

language = "English (US)",

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PY - 1998/12/15

Y1 - 1998/12/15

N2 - We have identified the seismic phase PKJKP, traveling through the inner core of the Earth as a shear wave, in intermediate-period (2-10 s) records of the deep 1996 Flores Sea earthquake at eight stations of the French seismic network. This constitutes direct evidence of the solidity of the inner core which, while generally recognized, was until now only inferred from indirect evidence. The arrival times on stacked seismograms require a shear-wave velocity at the top of the inner core β(ICB) = 3.65 km/s in agreement with values suggested from normal mode observations. Julian et al.'s 1972 observation of a lower velocity (2.95 km/s) is easily reconciled with our result if interpreted as the surface reflection pPKJKP. The high Poisson ratio (v = 0.44) can be reconciled with a normal crystalline structure without invoking partial melting on account of the overwhelming pressure at the center of the Earth.

AB - We have identified the seismic phase PKJKP, traveling through the inner core of the Earth as a shear wave, in intermediate-period (2-10 s) records of the deep 1996 Flores Sea earthquake at eight stations of the French seismic network. This constitutes direct evidence of the solidity of the inner core which, while generally recognized, was until now only inferred from indirect evidence. The arrival times on stacked seismograms require a shear-wave velocity at the top of the inner core β(ICB) = 3.65 km/s in agreement with values suggested from normal mode observations. Julian et al.'s 1972 observation of a lower velocity (2.95 km/s) is easily reconciled with our result if interpreted as the surface reflection pPKJKP. The high Poisson ratio (v = 0.44) can be reconciled with a normal crystalline structure without invoking partial melting on account of the overwhelming pressure at the center of the Earth.

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Detection of PKJKP at intermediate periods by progressive multi-channel correlation

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