Handan Zhang

Using reflective waves method to comprehensively identify and catalog the seismic anisotropy of the Core-Mantle Boundary to establish a robust mapping

PhD project title:

Mapping Core-mantle boundary anisotropy with core-reflected P waves.

Project description:

Seismic anisotropy is relevant to mantle flow, and mapping the anisotropy of the Core-Mantle Boundary (CMB) could enhance our understanding of mantle flow patterns. However, there is currently no convincing evidence that Large Low Shear Velocity Provinces (LLVPs) exhibit anisotropic features. Research on the CMB and LLVPs has predominantly relied on the analysis of refractive S and P waves, particularly through examining splitting and differences in vertical and horizontal arrival times [Long, 2009][Alexander and Phinney, 1966][Ni and Helmberger, 2001].

Nevertheless, the refractive wave method has its limitations and disadvantages: 

• magnitude 6.5 or larger sources are required because of the rapid amplitude decrease with ob- serving distance in the shadow region, especially for high frequencies
• at least two recording stations in the shadow region, on nearly the same azimuth from the source, are needed in order to remove source radiation effects
• interpreting observed diffracted waves in terms of theory is difficult

This project aims to deploy novel observations of core-reflected P waves to map the anisotropy of the CMB.