South Sudan

South Sudan occupies a complex geological position straddling the northern extension of the East African Rift System and the ancient basement of the Central African Shield. The East African Rift enters South Sudan from Uganda and Kenya through the Albert Rift to the southwest, and a system of Mesozoic and Cenozoic rift basins — including the Blue Nile Rift, the Central Sudan Rift, and the Muglad and Blue Nile basins — extends through the country northward into Sudan. These rift structures generate occasional moderate seismicity, particularly in the west and southwest of the country.

The region around the Uganda-South Sudan border, including the area near the Albert Rift and the Imatong Mountains, has experienced moderate earthquakes. The Democratic Republic of Congo border region near Tambura has also shown occasional seismicity. A [[magnitude]] 5.5 event struck near Kapoeta in eastern South Sudan in January 2021, causing felt shaking across the region.

The geology of South Sudan is dominated by Precambrian basement — part of the Nile Craton and associated mobile belts. These ancient rocks were deformed during multiple Proterozoic orogenic episodes, and the resulting [[fault]] structures can be reactivated under modern stress. The Cretaceous rift basins overlying this basement, however, represent the primary seismogenic zones where the crust is thinner and more susceptible to deformation.

Historical earthquake records for South Sudan are extremely limited, partly because seismic monitoring infrastructure is essentially absent and partly because the country's prolonged civil conflicts have made scientific fieldwork impossible. Events that do occur are typically characterised based on regional network data from Uganda, Ethiopia, or Sudan, with correspondingly poor location accuracy.

The tectonic setting involves South Sudan sitting near the diffuse boundary between the Nubian and Somalian sub-plates, in a zone where the rift geometry is transitional and complex. The [[seismic-wave]] propagation in the region is affected by the varying lithospheric thickness between the ancient craton domains and the younger rift basins. Seismic hazard in South Sudan is assessed as low-to-moderate in the southwest and very low in the northeast, though the data to support this assessment are sparse.