Short-Period and Broadband Seismic Investigation of the Core-Mantle Boundary and D'

9814811

Revenaugh

This research involves the mapping of a feature just above the core-mantle boundary referred to as the ULVZ (Ultra-Low Velocity Zone). It is a thin layer (less than 40 km thick) characterized by greatly depressed compressional and shear velocities indicating that it is probably partially molten and possibly chemically differentiated from the overlying mantle. Inferred properties of the ULVZ make it an efficient conveyer of heat from the core, a shaper of the geodynamo, and a potential storehouse for deep mantle volatiles. Correlation of core-mantle boundary ULVZ patches with hotspot volcanism at the earth's surface suggests a link to plume genesis, specifically that instability within or on top of the layer may orchestrate heat flow from the deep mantle. To date, 44% of the core-mantle boundary has been probed for the presence or absence of a detectable ULVZ. 25% of the sampled core-mantle boundary is overlain by an ULVZ. This work involves extension of coverage to new areas and more detailed investigation of previously covered areas to refine seismic parameters that will be useful to the mineral physics and mantle dynamics scientists.