Mapping Small-Scale Structure Above the Core-Mantle Boundary

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WysessionEAR-0207751 The aim of this project is to advance our understanding of the geophysics of the Core-mantle boundary (CMB) region through examination of small-scale regional variations in shear waves that interact with D", the base of the mantle. Specifically, the investigators will look for direct evidence of the foundations of mantle plumes, chemical boundary layers, and subducted slabs at the CMB with the increased resolution provided by the growing database of broadband array data. The CMB displays complexity and variability unequalled within the sub-lithospheric earth. As a major chemical and thermal boundary layer between the rocky mantle and liquid outer core, the CMB likely plays significant roles in the circulation of mass, as well as the transfer of heat both within and between the mantle and core. The investigators will specifically address the following questions: 1) Do mantle plumes form in D"? 2) Are there laterally discrete chemical boundary layers within D"? 3) Do slabs reach the CMB? One-dimensional models of D" structure will be generated using reflectivity synthetics, but final models will also be tested with fully 3D synthetics using the spectral-element method of Komatitsch and Tromp (2001), which has been installed on Washington University's SGI parallel processing machine.