Deaggregation of Probabilistic Seismic Hazard for Designated Cities in Ghana

Abstract

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.