CSEDI: Structure and Dynamics of Large-Scale Lower Mantle Compositional Heterogeneity

Research project

Description

This two-year proposal seeks funding for seismological imaging of lower mantle heterogeneity beneath the Pacific Ocean, and numerical convection simulations to put the seismic imaging into a dynamically consistent framework; thus the proposed multidisciplinary work combines seismological (PI Garnero) and geodynamics (PI McNamara) analyses. Recent seismological work has added great detail to deep mantle structure beneath the Pacific, with evidence for large low shear velocity provinces (LLSVPs) that are denser than and chemically distinct from the surrounding mantle. Smaller scale structure includes ultra-low velocity zones (ULVZs) that may preferentially reside at LLSVP margins. This proposed work aims to continue high resolution analyses that suggest sharp LLSVP edges extending well up off the core-mantle boundary (CMB), and associated phenomena that depend strongly on LLSVP and mantle properties, including: ULVZ location and structure, CMB topography in vicinity of LLSVP edge, strong heterogeneity within the LLSVP, and relationship to plume upwelling off the LLSVP top. Seismic data from southwest Pacific subduction zones recorded in North American densely sample the LLSVP beneath the Pacific Ocean, especially beneath Hawaii, and is the focus area of the proposed work. Seismic findings will inform and be informed by geodynamic simulations that include LLSVP structures. Particular attention will be given to LLSVP morphology and internal structure in the dynamical calculations, as these features will be seismically imaged.
StatusFinished
Effective start/end date5/15/124/30/15

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lower mantle
province
low velocity zone
core-mantle boundary
geodynamics
mantle
ocean
simulation
mantle structure
subduction zone
seismic data
upwelling
plume
convection
topography