Abstract
AbstractRayleigh wave group and phase velocity measurements obtained from ambient noise and earthquake data at 51 broadband stations were used to construct the first 3‐D crustal and upper mantle shear wave velocity model of Botswana. The model shows low crustal velocities associated with the Passarge and Nosop sedimentary basins, whereas the Kaapvaal, Zimbabwe, Maltahohe, and Congo Cratons are recognized by high mantle velocities. The lowest upper mantle shear wave velocity, beneath northeastern Botswana, is associated with the southwestern branch of the East African Rift System. This low‐velocity mantle anomaly appears to be linked to the crust of the Okavango Rift Zone and the location of the 3 April 2017 6.5 earthquake in central Botswana. We suggest that fluids or melt at the base of the crust from the southward continuation of the East African Rift Zone triggered the intraplate earthquake in an extensional tectonic setting.
Highlights
The African continent comprises several Archean cratons surrounded by younger Proterozoic fold belts
We suggest that fluids or melt at the base of the crust from the southward continuation of the East African Rift Zone triggered the intraplate earthquake in an extensional tectonic setting
Our results suggest that fluids from the East African Rift System in the upper mantle have triggered the intraplate earthquake as part of the ongoing rifting in southern Africa
Summary
The African continent comprises several Archean cratons surrounded by younger Proterozoic fold belts. The reworking of these cratonic blocks by accretion and rifting is fundamental for understanding the formation of the continent and the evolution of its crust. The Rehoboth Province and adjacent areas are presently covered by a thick sedimentary layer extending to more than 10 km in the Nosop and Passarge Basins (Pretorius, 1984). This hampers studies of the structure of the Rehoboth Province and adjacent mobile belts
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