Surface wave tomography and shear wave velocity structure of the Southwestern block of the Congo craton

DSpace/Manakin Repository

Show simple item record

dc.contributor.author Mangongolo, Azangi
dc.date.accessioned 2012-02-27T06:05:02Z
dc.date.available 2012-02-27T06:05:02Z
dc.date.issued 2012-02-27
dc.identifier.uri http://hdl.handle.net/10539/11350
dc.description M.Sc., Faculty of Science, University of the Witwatersrand, 2011 en_US
dc.description.abstract Rayleigh wave dispersion curves are used to invert for the group velocity maps of the southwestern block of the Congo craton. The group velocity maps were then inverted to obtain the three dimensional shear-wave velocity of the lithosphere beneath the region. In the process, the adjacent Kalahari craton and Damara mobile belt were also mapped to help constrain the southernmost edge of the Congo craton. To obtain the surface wave group velocity tomography, event-station dispersion curves of Rayleigh waves were measured using the multiple filter analysis method. Then the dispersion curves were inverted using the conjugate gradient least-square (CGLSQR) inversion method. To check the reliability of the result, a checkerboard test was performed. The 2-dimensional group velocities and 3-dimensonal shear-wave velocities were found to be faster beneath the southwestern block of the Congo craton and the Kalahari craton and slower in the Damara mobile belt. The group velocity map at 20s period shows that basins are 0 to 3% slower than PREM model. For longer period (50s to 120s), the Central and East African Rift system are ~ 5 % faster, cratons are 5 to 8% faster, and the adjacent mobile belts are 0 to 4% faster than the PREM model. The Afar depression is the slowest, up to 6% slower than the continental PREM model at all periods. The shear-wave velocity maps reveal that (1) the Afar area is the slowest (up to 8% slower than the IASP91 model), (2) the cratons are faster (up to 6% faster than IASP91) than the surrounding mobile belts (up to 2% faster than IASP91). The East African Rifts system is also slow (up to 5%). The Damara mobile belt constitutes a clear separation terrain between the Congo craton and the Kalahari craton. This result is consistent with previous studies by Pasyanos and Nyblade (2007), and Priestly et al. (2006, 2008), who also found faster shear-wave velocities beneath the Kalahari, Congo and Tanzania cratons. The relatively slow seismic velocities (-1 to 2% compared to IASP91) in the Proterozoic Damara mobile belt between the southwestern block of the Congo craton and the Kalahari craton are explained by the view that the Proterozoic lithosphere has hotter rock materials than the SW block of the Congo craton and the Kalahari craton. Our model of faster lithosphere beneath the SW block of the Congo and the Kalahari craton is also consistent with the model of strongly depleted (in basaltic components) lithosphere beneath these craton; compared to less depleted lithosphere beneath the DMB. en_US
dc.language.iso en en_US
dc.subject Surface waves en_US
dc.subject Tomography en_US
dc.subject Shear waves en_US
dc.subject Geophysics en_US
dc.title Surface wave tomography and shear wave velocity structure of the Southwestern block of the Congo craton en_US
dc.type Thesis en_US


Files in this item

This item appears in the following Collection(s)

Show simple item record

Search WIReDSpace


Advanced Search

Browse

My Account

Statistics