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
|Effective start/end date||12/1/09 → 11/30/13|
- National Science Foundation (NSF): $184,271.00
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