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.
