NSFGEO-NERC: Global ultralow-velocity zone properties from seismic waveform modeling

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The Earth's core-mantle boundary (CMB) region is of critical importance for understanding Earth dynamics and harbors a wide variety of heterogeneous structures. Ultra-low velocity zones (ULVZs) are regions of reduced seismic velocities at the CMB, which have been associated with hot spot volcanism,Large Igneous Provinces, core-mantle interaction and Large-Low Shear Velocity Provinces and thus are essential in assessing Earth dynamics. ULVZs are typically studied using seismic waveform analysis, but these studies suffer from large uncertainties in ULVZ parameters due to modeling tradeoffs. Fundamental questions related to the physical nature of ULVZs remain unanswered, including their compositional variability, size distribution, location with respect to other structures, and 3-D geometry. Additionally, only a small fraction of the CMB area has been probed for ULVZs. Here, we seek to fundamentally reassess ULVZs from all angles, and reduce uncertainties in their properties, location, and composition.