摘要
SeismicPvelocitystructureisdeterminedfortheupper500kmoftheinnercoreandlowermost200kmoftheoutercorefromdifferentialtraveltimesandamplituderatios.ResultsconfirmtheexistenceofagloballyuniformFregionofreducedPvelocitygradientinthelowermostoutercore,consistentwithironenrichmentneartheboundaryofasolidifyinginnercore.Pvelocityoftheinnercorebetweenthelongitudes45oEand180oE(quasi-EasternHemisphere)isgreaterthanorequaltothatofanAK135-Freferencemodelwhereasthatbetween180oWand45oE(quasi-WesternHemisphere)islessthanthatofthereferencemodel.Observationofthisheterogeneitytoadepthof550kmbelowtheinnercoreandtheexistenceoftransitionsratherthansharpboundariesbetweenquasi-hemispheresfavoreithernoorveryslowinnercoresuperrotationoroscillationswithrespecttothemantle.DegreeoneseismicheterogeneitymaybebestexplainedbyactiveinnercorefreezingbeneaththeequatorialIndianOceandominatingstructureinthequasi-EasternHemisphereandinnercoremeltingbeneathequatorialPacificdominatingstructureinthequasi-WesternHemisphere.Variationsinwaveformsalsosuggesttheexistenceofsmaller-scale(1to100km)heterogeneity.
出版日期
2013年05月15日(中国期刊网平台首次上网日期,不代表论文的发表时间)