This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615–2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study—Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km.

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A probabilistic seismic hazard study based on the values of spectral acceleration (SA), and peak ground acceleration (PGA) has been performed for the southern part of Ghana. Three conceivable seismic sources inside and near Ghana were identified and considered based on a modern and integrated earthquake catalog of over a century (1615–2009). Epistemic uncertainties associated with input parameters were considered and implemented in the seismic hazard calculation using a logic tree method. These included the chosen suitable ground-motion attenuation equations. Thereafter, the deaggregation of the seismic hazard, expressed in magnitude and distance, for selected cities in Ghana was estimated to aid in the understanding of the contributions to the hazard of various seismic sources. Deaggregation of the seismic hazard was estimated for SA of 0.2 s, and 1.0 s as well as PGA at 10% probability of exceedance in 50 years. All in all, the results show that the sources located close to the cities contribute most to their seismic hazard, especially for PGA. More distance sources only contribute to the hazard at longer periods (e.g. 1.0s) The importance of the outcome of this type of study is that deaggregation of the seismic hazard offers valuable data of the seismic sources that contribute towards the hazard at a specific location. This information can be used to decide on the scenario-based ground-motion time histories necessary for the seismic design of structures.