Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

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.

Seismogenic Fault Reactivation in Western Central Africa: Insights From Regional Stress Analysis

“…Overall, several studies have speculated that preexisting fractures are hosting earthquakes along the continental margins and interior of western Africa but lack details of the ambient stress field and the evidence for coseismic surface fault rupture or presence of active fault scarps (Amponsah, 2002; Ayele, 2002; Blundell, 1976; Bouka Biona & Sounga, 2001; Kutu, 2013; Olugboji et al., 2021; Sykes, 1978). Here, with our stress analysis, we provide insight into the control of contemporary stress regimes on the occurrence of intraplate earthquakes in the region.…”

Seismic risk analysis for large dams in West Coast basin, southern Ghana

“…Accra's earthquakes are mainly attributed to the reactivation of faults in the Romanche fracture zone, specifically the Coastal Boundary fault and Akwapim fault (Kutu 2013;Musson 2014;Ahulu et al 2018). The Coastal Boundary fault became tectonically active in Jurassic times and is still active (Ahulu et al 2018).…”

Application of Shore-Based Video and Unmanned Aerial Vehicles (Drones): Complementary Tools for Beach Studies

“…The continental shelf off Dzita is narrow (~25-35 km), limited by east-west offsetting by the Romanche fracture zone, a left-lateral transform fault. The Volta delta developed in a large salient trap created by left-lateral offsetting of the coast and continental shelf of Ghana, probably by the Romanche fracture zone [27], a major fracture zone impinging on the Bight of Benin shelf [28]. The wave setting along the coastline is the cyclone-and storm-free West Coast Swell Environment as defined by [29], and the prevailing swells are moderate to high energy (H = 1.36 m), long period (T = 9.6 s) southwesterly swells from the Atlantic [30].…”