Mapping the Core-Mantle Boundary Using Sdiff Postcursors ...

• Main Author: Martin, Carl
• Format: Thesis
• Language: English
• Published: Apollo - University of Cambridge Repository 2023
• Subjects: Core-Mantle Boundary; Deep Earth; Earth Sciences; Lower Mantle; Seismology; ULVZs; Iceland
• Online Access: https://dx.doi.org/10.17863/cam.109540; https://www.repository.cam.ac.uk/handle/1810/369951

The core-mantle boundary – the interface between the rocky mantle and the fluid iron outer core – is host to a diverse collection of phenomena across all length scales. At the largest length scales, continent-sized structures characterised by low velocity anomalies lie opposite to each other on the core-mantle boundary. These structures, known as large low shear velocity provinces (LLSVPs), are predominantly situated beneath the Pacific Ocean and the African continent. Smaller, more extreme phenomena (10s km thick, up to 100s km wide, dVs -10–50%, dVp -5–25%) have been identified on top of the core-mantle boundary, called ultra-low velocity zones (ULVZs). The largest of these anomalies have been associated with whole-mantle plumes at the base of major hotspots (Hawaii, Iceland, Samoa, and Galapagos), and have been suggested to act as a plume root and geochemical reservoir. In this thesis, we use the S core-diffracted phase (Sdiff) to detect ULVZs. Sdiff wavefronts propagating across the core-mantle boundary ...