Large earthquakes away from plate boundaries pose a significant threat
to human lives and infrastructure, but such events typically occur on
previously unknown faults. Most cases of intra-plate seismicity result
from compression related to far-field plate boundary stresses. The April
2017 Mw 6.5 earthquake in central Botswana, and subsequent events,
occurred in a region with no previously known large earthquakes,
occurred away from major present day tectonic activity, and accommodate
extension rather than compression. Here, we present results from an
integrated geophysical study that suggests the recent earthquakes may be
a sign of future activity, controlled by the collocation of a weak upper
mantle and weak crustal structure, between otherwise strong Precambrian
blocks. Magnetotelluric data highlights Proterozoic continent accretion
structure within the region, and shows that recent extension and
seismicity occurred along ancient thrust faults within the crust. Our
seismic velocity and resistivity models suggest a weak zone in the
uppermost mantle, that does not persist to greater depths, and is
therefore unlikely to represent mantle upwelling. The Botswana events
may therefore be indicative of top-down extension as a response to large
scale extensional forces.