Joint Seismic tomography for the Africa plate and underlying mantle

Theme: Solid Earth Dynamics

Primary Supervisor:

James Hammond

Department of Earth and Planetary Sciences, BBK

James Hammond's Profile Picture

Project Description:

The African plate appears to be underlain by significant mantle upwellings with possible deep lower mantle roots. These are thought to have triggered the ongoing rifting in the East African rift, with considerable associated seismic and volcanic hazard and are responsible for the current high elevations across East-Africa, controlling surface processes and affecting drainage patterns.

Seismic imaging is the most powerful method to study structure of the lithosphere and mantle. In Africa, the resolution of such images has been limited by the distribution of stations and earthquake sources. However, over the past 20 years, many regional and local seismic networks have been installed across the continent and dramatically expanded seismic data sets. Our team has been heavily involved in this and has built separate models for parts of the continent using either body wave travel times (Hammond), receiver functions (David Thompson, Cardiff) or surface wave data (Stewart Fishwick, Leicester).

This PhD will aim to bring all these data together and using cutting edge inversion techniques (Nick Rawlinson, Cambridge), will jointly invert these data for lithospheric and mantle structure beneath Africa. Interpretation of the images in terms of temperature and possibly composition and presence of melt will be done using methods developed by Saskia Goes (Imperial) and implications of these thermochemical structures on uplift and subsidence will be evaluated using the expertise from Gareth Roberts (Imperial) and his group.

Policy Impact of Research:

Mantle upwellings beneath Africa are thought to be responsible for continental breakup 30 million years ago and the subsequent volcanic and earthquake hazards today. They are also responsible for significant uplift and thus control river drainage patterns and subsequent delivery of sediments to margins, a key factor in hydrocarbon development.

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