The Kordofan earthquakes, central Sudan

Geophysical studies have revealed extensive rift systems throughout Central Africa, among them the White Nile Rift runnng SE-NW across central Sudan. Few earthquakes have been detected teleseismically in areas of Sudan away from the East African or Red Sea Rift systems. Relocations presented here confirm three earthquakes to have occurred at shallow depth at the NW extreme of the White Nile Rift, around Jebel Dumbeir, Kordofan province. Ambiguity in a teleseismic P-wave first-motion solution for the 9 October 1966 0648GMT event is resolved by use of the P/pP/sP relative amplitude method. The fault plane is near-vertical, striking to 005–025° with a downthrow to the SE and a minor sinistral strike-slip component. This is consistent with ground deformation and location of an aftershock. Its downthrow direction appears to reflect subsidence of the White Nile Rift and central Sudan. Its strike is common with present-day activity in the Ethiopian Rift, suggesting that a near ESE-WSW stress regime persists across central and southern Sudan.