The uppermost mantle shear wave velocity structure of eastern Africa from Rayleigh wave tomography: constraints on rift evolution

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dc.contributor.authorO’Donnell, J.P., Adams, A., Nyblade, A.A., Mulibo G.D., and Tugume F
dc.date.accessioned2021-04-20T14:16:51Z
dc.date.available2021-04-20T14:16:51Z
dc.date.issued2013-05-01
dc.description.abstractAn expanded model of the 3-D shear wave velocity structure of the uppermost mantle beneath eastern Africa has been developed using earthquakes recorded by the AfricaArray East African Seismic Experiment in conjunction with data from permanent stations and previously deployed temporary stations. The combined data set comprises 331 earthquakes recorded on a total of 95 seismic stations spanning Kenya, Uganda, Tanzania, Zambia and Malawi. In this study, data from 149 earthquakes were used to determine fundamental-mode Rayleigh wave phase velocities at periods ranging from 20 to 182 s using the two-plane wave method, and then combined with the similarly processed published measurements and inverted for a 3-D shear wave velocity model of the uppermost mantle. New features in the model include (1) a low-velocity region in western Zambia, (2) a high-velocity region in eastern Zambia, (3) a low-velocity region in eastern Tanzania and (4) low-velocity regions beneath the Lake Malawi rift. When considered in conjunction with mapped seismicity, these results support a secondary western rift branch striking southwestwards from Lake Tanganyika, likely exploiting the relatively weak lithosphere of the southern Kibaran Belt between the Bangweulu Block and the Congo Craton. We estimate a lithospheric thickness of ∼150–200 km for the substantial fast shear wave anomaly imaged in eastern Zambia, which may be a southward subsurface extension of the Bangweulu Block. The low-velocity region in eastern Tanzania suggests that the eastern rift branch trends southeastwards offshore eastern Tanzania coincident with the purported location of the northern margin of the proposed Ruvuma microplate. Pronounced velocity lows along the Lake Malawi rift are found beneath the northern and southern ends of the lake, but not beneath the central portion of the lake.en_US
dc.description.sponsorshipThis study was funded by National Science Foundation grants OISE-0530062, EAR-0440032 and EAR-0824781en_US
dc.identifier.citationJ. P. O’Donnell, A. Adams, A. A. Nyblade, G. D. Mulibo, F. Tugume, The uppermost mantle shear wave velocity structure of eastern Africa from Rayleigh wave tomography: constraints on rift evolution, Geophysical Journal International, Volume 194, Issue 2, August 2013, Pages 961–978, https://doi.org/10.1093/gji/ggt135en_US
dc.identifier.doidoi.org/10.1093/gji/ggt135.
dc.identifier.urihttp://hdl.handle.net/20.500.11810/5644
dc.language.isoenen_US
dc.publisherOxforden_US
dc.subjectMantle processes, Seismicity and tectonics, Surface waves and free oscillations, Seismic tomography, Dynamics of lithosphere and mantle, Africaen_US
dc.titleThe uppermost mantle shear wave velocity structure of eastern Africa from Rayleigh wave tomography: constraints on rift evolutionen_US
dc.typeJournal Article, Peer Revieweden_US
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