Ghana

Ghana occupies a structurally interesting position on the West African craton. While much of the country sits on stable Precambrian basement, southern Ghana is transected by the Akwapim Fault Zone — a northeast-trending ancient structural lineament that has been reactivated periodically since the Proterozoic. The Akwapim-Togo ranges, a series of northeast-trending ridges that cross southeastern Ghana into Togo, follow this zone of structural weakness. Southern Ghana, including the capital city Accra, experiences moderate seismicity by West African standards, with several damaging historical earthquakes recorded in the coastal zone.

The most significant earthquake in Ghana's recorded history occurred on 22 June 1939, centered near Accra. The earthquake reached an estimated [[magnitude]] of 6.5 and killed approximately 17 people while injuring over 130. The [[epicenter]] was located in the Gulf of Guinea just offshore from Accra, and the shaking was intensified by the soft coastal sediments on which parts of the city are built. The event caused widespread structural damage to buildings in Accra and was felt across the coastal region of Ghana and in adjacent parts of Togo.

An earlier significant event struck on 10 July 1862 near Accra, reported to have severely damaged many buildings in the then-colonial capital. A magnitude 6.0 event in 1906 also affected the Accra region. More recently, a magnitude 5.1 earthquake in December 1997 near the Akwapim ranges was widely felt in Accra and surrounding districts.

The Volta Lake, impounded by the Akosombo Dam since 1965, sits in a pre-existing depression along the ancient Volta Basin. The filling of the reservoir was associated with a moderate increase in local seismicity — a well-documented phenomenon of reservoir-induced seismicity — though the events recorded in the 1960s and 1970s near the lake were of low [[magnitude]] and not damaging.

The tectonic setting of Ghana involves reactivation of Proterozoic [[fault]] systems under the contemporary northeast-southwest compression of the African plate. The Romanche and Chain transform fault zones, which intersect the African continent offshore from Ghana in the Gulf of Guinea, represent ancient oceanic fracture zones that have been dormant since the Cretaceous but may marginally influence the stress field in coastal southern Ghana. The [[seismic-wave]] propagation characteristics in Ghana are dominated by the ancient but mechanically heterogeneous craton, which can efficiently transmit energy over long distances from moderate earthquakes.