Probing the Earths Outer Core for a Stratified Layer

Project: Research project

Description

An outstanding question in deep Earth science is the degree to which the mantle and core are not in equilibrium. Disequilibrium processes should result in chemical reactions at the core-mantle boundary (CMB) that give rise to fine-scale outermost core and lowermost mantle layering. Recent geochemical, dynamical, and geomagnetism considerations have supported core-side layering, but such a layer has not been unambiguously imaged. Seismic studies of the outermost core utilize SmKS waves: mantle S-waves that convert to P-waves upon entering the core, reflect m-1 times from the underside of the CMB, then convert back to an S-wave for the final mantle leg. SmKS phases are the only seismic waves that have turning depths in outermost core. Past work indicates reduced P velocities at the top of the outer core. However, SmKS phases can be significantly contaminated by lower mantle heterogeneities, which past work has not adequately accounted for. Also, a stably stratified outer core layer must be less dense, and hence predicts that the velocity of such a layer will be elevated, not decresed. Thus, there is an important need to better image the outermost core, while accounting for anomalous mantle structure.vnd.ms-ex
StatusFinished
Effective start/end date12/1/0911/30/13

Funding

  • National Science Foundation (NSF): $184,271.00

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outer core
mantle
core-mantle boundary
S-wave
mantle structure
geomagnetism
lower mantle
Earth science
disequilibrium
seismic wave
chemical reaction
P-wave