Hemispherical variations in seismic velocity at the top of the Earth's inner core

Nature
F Niu, Lianxing Wen

Abstract

Knowledge of the seismic velocity structure at the top of the Earth's inner core is important for deciphering the physical processes responsible for inner-core growth. Previous global seismic studies have focused on structures found 100 km or deeper within the inner core, with results for the uppermost 100 km available for only isolated regions. Here we present constraints on seismic velocity variations just beneath the inner-core boundary, determined from the difference in travel time between waves reflected at the inner-core boundary and those transmitted through the inner core. We found that these travel-time residuals-observed on both global seismograph stations and several regional seismic networks-are systematically larger, by about 0.8 s, for waves that sample the 'eastern hemisphere' of the inner core (40 degrees E to 180 degrees E) compared to those that sample the 'western hemisphere' (180 degrees W to 40 degrees E). These residuals show no correlation with the angle at which the waves traverse the inner core; this indicates that seismic anisotropy is not strong in this region and that the isotropic seismic velocity of the eastern hemisphere is about 0.8% higher than that of the western hemisphere.

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Citations

May 12, 2010·Proceedings of the National Academy of Sciences of the United States of America·Maurizio MattesiniRajeev Ahuja
Jun 13, 2012·Proceedings of the National Academy of Sciences of the United States of America·Zhu MaoHo-Kwang Mao
May 22, 2010·Science·Bruce A Buffett
Oct 12, 2005·Proceedings of the National Academy of Sciences of the United States of America·D HelmbergerM Gurnis
Dec 28, 2006·Proceedings of the National Academy of Sciences of the United States of America·Aimin CaoBarbara Romanowicz
Jun 29, 2013·Scientific Reports·M MattesiniR Ahuja
Feb 6, 2018·Scientific Reports·Marian IvanRami Hofstetter
Aug 6, 2010·Nature·Michael I Bergman
Aug 2, 2017·Nature Communications·Dongdong Tian, Lianxing Wen
Sep 27, 2008·Science·Benoit Langlais, Hagay Amit

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