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 | |
| State | Published - Dec 15 1998 |
Funding
We thank Commissariat à 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]
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