کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4677185 1634792 2013 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Rolling hills on the core–mantle boundary
ترجمه فارسی عنوان
تپه های نوردی در مرز مرجانی هسته ای
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
چکیده انگلیسی

Recent results suggest that an iron-rich oxide may have fractionally crystallized from a primordial magma ocean and settled on the core–mantle boundary (CMB). Based on experimental results, the presence of only a few percent of Fe-rich oxide could slow seismic waves down by several percent. This heavy layer can become highly undulating as predicted from dynamic modeling but can remain as a distinct structure with uniform velocity reductions. Here, we use the large USArray seismic network to search for such structures. Strong constraints on D″ are provided by the core-phase SKS where it bifurcates, containing a short segment of P-wave diffractions (Pd) when crossing the CMB, called SKSd. Synthetics from models with moderate velocity drops (less than 10%) involving a layer with variable thickness, perhaps a composite of sharp small structures, with strong variation in thickness can explain both the observed SKSd waveforms and large scatter in differential times between SKKS and SKS. A smooth 3D image is obtained from inverting SKSd waveforms displaying rolling-hills with elongated dome-like structures sitting on the CMB. The most prominent one has an 80-km height, ∼8° length, and ∼4° width, thus adding still more structural complexity to the lower mantle. We suggest that these results can be explained by a dynamically-stabilized material containing small amounts (∼5%) iron-rich (Mg,Fe)O providing a self-consistent physical interpretation.


► Low velocity structure on CMB with moderate velocity reduction.
► Construct 3D shape of this structure.
► Iron-rich oxide could be the physical interpretation for this structure.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 361, 1 January 2013, Pages 333–342
نویسندگان
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