M 5.9 - 20 km N of Cyangugu, Rwanda

Tectonic Summary

The earthquake occurred in the Western Rift of the East African rift system. The East African rift system is a diffuse, approximately 3000-km-long, zone of crustal extension that passes through eastern Africa from Djibouti and Eritrea on the north to Malawi on the south and that constitutes the boundary between the Africa plate on the west and the Somalia plate on the east. At the earthquake's latitude, the Africa and Somalia plates are spreading apart at a rate of about four millimeters per year. The earthquake occurred near Lake Kivu, the basin of which was created by normal faulting similar to that which produced the February 3 earthquake. The largest earthquake to have occurred in the rift system since 1900 had a magnitude of about 7.6. The epicenter of the February 3, 2008, earthquake is within several tens of kilometers of the epicenter of a magnitude 6.2 earthquake that killed two people in Goma in October 2002. Earthquakes within the East African rift system occur as the result of both normal faulting and strike-slip faulting.