Electrical Structure of the Earth's Upper Mantle

全球地震层析成像、板块运动重建和俯冲板块命运的区域层析成像研究对地球上地幔大尺度结构的限制影响了我们对地球对流的看法。证据支持上地幔的大规模、体积横向非均质性，以及410和660公里处的内部不连续性。全球地磁观测站网的长周期电磁感应数据可以解决大尺度的地幔结构横向变化问题。PI建议开发和应用球形三维反演方案来成像地球上地幔电导率的横向变化。反演将基于PI最近开发的球形有限元代码。利用反演代码和其他地球物理技术的限制，PI提出：1)验证长周期全球感应数据与上地幔地震层析成像结果一致的假设；2)开发正则化算法并反演上地幔三维电导率结构的全球感应数据集；3)将电偶效应和海洋效应纳入现有的非均质球电磁感应正演模型。这项工作可能会在地幔电导率变化的三维建模和解释方面取得有益的进展，并为地幔动力学提供独立的约束条件。

Everett 9526651 Constraints on the large-scale structure of Earth's upper mantle from global seismic tomography, plate motion reconstructions, and regional tomographic studies on the fate of subducting slabs influence our view of convection in the planet. The evidence supports large-scale, volumetric lateral heterogeneity in the upper mantle, in addition to internal discontinuities at 410 and 660 km. Long-period electromagnetic induction data from the worldwide magnetic observatory network can resolve large-scale lateral variations in mantle structure. The PI proposes to develop and apply a spherical 3-d inversion scheme for imaging lateral variations in upper mantle conductivity of the earth. The inversion will be based on the PI's recently developed spherical finite element code. Using the inversion code, and constrains from other geophysical techniques, the PI proposes to 1) test the hypothesis that long period global induction data are consistent with upper mantle seismic tomographic results, 2) develop a regularization algorithm and invert the global induction data set for the three-dimensional electrical conductivity structure of the upper mantle, and 3) incorporate galvanic and oceanic effects into the existing forward model of electromagnetic induction in a heterogeneous sphere. The proposed work is likely to lead to useful progress on 3-d modeling and interpretation of mantle conductivity variations and provide independent constraints on mantle dynamics.