Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio

Xiangfang Zeng; Sidao Ni

doi:10.1007/s12583-013-0371-9

Volume 24 Issue 5

Oct 2013

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Journal of Earth Science > 2013 > 24(5): 716-724.

Xiangfang Zeng, Sidao Ni. Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio. Journal of Earth Science, 2013, 24(5): 716-724. doi: 10.1007/s12583-013-0371-9

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Xiangfang Zeng, Sidao Ni. Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio. Journal of Earth Science, 2013, 24(5): 716-724. doi: 10.1007/s12583-013-0371-9

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Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio

doi: 10.1007/s12583-013-0371-9

Xiangfang Zeng^{1, 2},
Sidao Ni^{3
,
,}

1.
CAS Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing, 100049, China
2.
Mengcheng National Geophysical Observatory, University of Science and Technology of China, Hefei, 230026, China
3.
State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, 430077, China

Funds:

the National Natural Science Foundation of China 41204044

the National Natural Science Foundation of China 40674027

the Fund of Chinese Academy of Sciences KZCX2-EW-121

More Information

Corresponding author: Sidao Ni, sdni@whigg.ac.cn
Received Date: 03 Dec 2012
Accepted Date: 02 Jun 2013
Publish Date: 01 Oct 2013

Abstract

Abstract

Shear velocity and density contrast across the inner core boundary are essential for studying deep earth dynamics, geodynamo and geomagnetic evolution. In previous studies, amplitude ratio of PKiKP/PcP at short distances and PKiKP/P at larger distances are used to constrain the shear velocity and density contrast, and shear velocity in the top inner core is found to be substantially smaller than the PREM prediction. Here we present a large dataset of PKiKP/P amplitude ratio measured on 420 seismic records at ILAR array in Alaska for the distance range of 80°–90°, where the amplitude ratio is sensitive to shear velocity and density contrast. At high frequency (up to 6 Hz), mantle attenuation is found to have substantial effects on PKiKP/P. After the attenuation effects are taken into account, we find that the density contrast is about 0.2–1.0 g/cm³, and shear velocity of inner core is 3.2–4.0 km/s, close to the PREM (Preliminary Reference Earth Model) prediction (0.6 g/cm³ and 3.5 km/s, respectively). The relatively high shear velocity in inner core does not require large quantities of defects or melts as proposed in previous studies.
- inner core boundary,
- shear velocity of inner core,
- density contrast,
- core phase

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References(48)

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Constraining Shear Wave Velocity and Density Contrast at the Inner Core Boundary with PKiKP/P Amplitude Ratio

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