Geophysics Project: Origin of the vast height difference between the African and Pacific LLSVPs
Supervised by Dr. M.M. Li & E. Garnero
The Large Low Shear Velocity Provinces (LLSVPs) are the largest structures in the lower mantle. They have been discovered decades ago, but their morphology and what causes their morphology remain unclear. In this new contribution, we, for the first time, constrain the maximum height of the two LLSVPs from 17 global shear wave velocity seismic models. We find that the African LLSVP is ~1,000 km higher than the Pacific LLSVP. We then perform systematic high-resolution geodynamic models to show that the height of LLSVPs is mainly controlled by the intrinsic density of LLSVP materials and the viscosity of the surrounding mantle. With ~1,000 numerical models, we show that the best explanation for the vast height difference between the two LLSVPs is that the African LLSVP is less dense, and thus less stable than the Pacific LLSVP.
It is the first time to demonstrate that the African LLSVP should be less dense than Pacific LLSVP at the present-day. Therefore, the two LLSVPs may have different densities and compositions. Our combination of the analysis of seismic results and the geodynamic modeling provides new insights on the nature of the Earth’s largest structures in the deep interior and their interaction with the surrounding mantle.
It is the first time to demonstrate that the African LLSVP should be less dense than Pacific LLSVP at the present-day. Therefore, the two LLSVPs may have different densities and compositions. Our combination of the analysis of seismic results and the geodynamic modeling provides new insights on the nature of the Earth’s largest structures in the deep interior and their interaction with the surrounding mantle.