Investigating African Mantle Structure with Adaptively Parameterized P-wave Tomography

Abstract:

Africa is home to a variety of ‘textbook’ tectonic features, such as the Cameroon Volcanic Line, the African Superswell, and the Afar triple junction; yet, the driving forces associated with these features are uncertain. Numerous global- and continental-scale tomographic images have been used to investigate the connections between surface features in Africa and the underlying mantle. However, the role of mantle plumes, including the African Superplume, small-scale convection, and other directed asthenospheric flow remains debated. Part of the uncertainty stems from resolution issues associated with the tomographic methods that have been employed. To further address how mantle processes influence surface tectonic features, we are developing a new P-wave tomographic model for the African continent. Our dataset includes more than 25 million global travel-time residuals acquired from the International Seismological Centre, augmented with more than 41,000 travel-time residuals measured from various African seismic networks. Further, we employ an adaptively parameterized grid that provides improved resolution compared to tomographic methods that use regularly-spaced gridding. By allowing the data sampling density to constrain the grid parameters, increased resolution is obtained in areas with significant raypath coverage without over-emphasizing poorly sampled regions and without averaging out small-scale structures. Preliminary results will be shared.