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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, B10307, doi:10.1029/2004JB002976, 2004

Regional variations in the uppermost 100 km of the Earth's inner core

Anastasia Stroujkova

Physics Department, University of Connecticut, Storrs, Connecticut, USA


Vernon F. Cormier

Physics Department, University of Connecticut, Storrs, Connecticut, USA


Abstract

The structure of the uppermost 100 km of the inner core was examined from PKIKP and PKiKP waveforms in the distance range of 118°–140°. We found evidence of a low-velocity layer in the uppermost inner core in the equatorial region predominantly located between longitude 20°W to 140°E. In the latitudinal direction the anomaly is detectable from 35°S beneath the Indian Ocean to 60°N underneath Asia. The maximum thickness of the low-velocity layer inferred from waveform modeling is 40 km with velocity jump of about 3%. We speculate that this layer may represent newly solidified core in the area where vigorous compositional convection in the outer core coincides with new crystal growth in the inner core.

Received 15 January 2004; accepted 15 July 2004; published 16 October 2004.

Keywords: inner core; seismic phases; PKiKP; PKIKP; travel times.

Index Terms: 7207 Seismology: Core and mantle; 7203 Seismology: Body wave propagation; 7260 Seismology: Theory and modeling; 8124 Tectonophysics: Earth's interior—composition and state.

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Citation: Stroujkova, A., and V. F. Cormier (2004), Regional variations in the uppermost 100 km of the Earth's inner core, J. Geophys. Res., 109, B10307, doi:10.1029/2004JB002976.