Abstract
For four centuries now, southern Ghana has been known to be seismically active, and there is no clear geological explanation for the cause of the seismicity. By evaluating new field data and information with re-interpreted historical earthquake data of southern Ghana, the nature of the seismicity of southern Ghana has been elucidated. The mutual connection between the earthquake epicentres and the remote causes by Mid-Atlantic transform faults and fracture zones has been established. The seismic regions of southern Ghana have been linked separately to tectonic faults and activities of the St. Paul’s and Romanche transform-fracture zone systems offshore in the Gulf of Guinea to onshore. It is concluded that the seismicity of southern Ghana is due to tectonic activities of the St. Paul’s and Romanche transform-fracture systems. The Accra region earthquakes originate from reactivation of faults in the Romanche transform-fracture zone, and propagate onshore through Accra and environs. The Axim region earthquakes come from reactivated faults linked to the St Paul’s fracture zone, which go through southern Cote D’Ivoire to Ghana. Seismotectonic movements along the St Paul’s transform and fracture zones have quieted since 1879. But movement along the Romanche Transform fault and Fracture zone is active, causing ongoing seismicity of southern Ghana.
Highlights
Earthquakes are natural crustal stabilization phenomena caused by lithospheric faulting and adjustments that help maintain the crustal stability and spheroidal structure of the Earth
Previous recorded damaging and destructive earthquakes had been reported in places wide apart in southern Ghana, notably from the southwest in the districts of Axim and Elmina to the
Junner et al (1941) [1] gave the trend of the actual en echelon fissures on the ground between Fete and Weija in the Accra region as N30 ̊E (030 ̊) in a general direction that swung between northeast (045 ̊) and N60 ̊E (060 ̊) indicates a sinistral subvertical seismic shear faulting of the Accra region, which sense is consistent with the trend and sense of the Equatorial Atlantic transform and fracture zone systems of the St
Summary
Recent seismicity in southern Ghana has heightened the need to find explanation for the causes of the earthquake activities in Ghana. Most of the discussions in the literature of the seismicity of Ghana have focused predominantly on earthquakes of the Accra-Ho seismic region at southeastern Ghana, and seem to generalize that for the whole country [e.g. 6-8], inherently suggesting a common cause for the seismicity of the entire southern Ghana. This generalization oversimplifies the nature and understanding of the phenomenon in Ghana
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