What do Global Geoid Models Tell us About the Mantle Viscosity Profile?
Panasyuk, S.V. and B.H. Hager,Eos Trans. Am. geophys. Un., 78, F156, 1997. Abstract: Previous investigations of mantle viscosity structure based on models of the nonhydrostatic geoid typically have assumed a particular model of the distribution of internal density anomalies. Densities were typically converted from a seismic velocity anomaly model, assuming a constant of proportionality, and/or from a geodynamical model of subducted slabs. The inferred viscosity profile was very sensitive to the assumed upper mantle density structure, e.g., slabs vs. tomography. We carry out a non-linear, multi-parameter, constrained inversion for the mantle viscosity profile based on fits to the geoid and/or free-air gravity field using tens of models of mantle density heterogeneity from tomographic and slab models. Using a compressible flow formulation, we simultaineously invert for velocity-to-density conversion factors in the upper and lower mantle for each model. A small number (three) of distinct
