Deterministic seismic ground motion modelling of the greater Accra Metropolitan area, Southeastern Ghana

Abstract

The seismic ground motion of the greater Accra Metropolitan Area has been modelled for land use planning and disaster mitigation. The deterministic computation, a hybrid method based on the modal summation and finite difference method was used. Using these techniques, the seismic ground motion along four profiles located in the metropolis has been computed. The 1939 earthquake of magnitude 6.5 (ML) was used as the scenario earthquake. Synthetic seismic waveforms from which parameters for engineering design such as peak ground acceleration, velocity and spectral amplifications have been produced along the geological cross sections. The peak ground acceleration and velocity computed for the metropolis ranges from 0.14 g to 0.57 g and 9.2 cms -1 to 37.1 cms-1, respectively. These correspond to intensity ranging from VII to IX on the Modified Mercalli Intensity scale. Areas in the metropolis underlain by unconsolidated sediments experience the largest shakings. The results illustrated represent a useful guide for civil engineers in the design of buildings in the metropolis for safe and sustainable development. © 2009 December Geological Society of South Africa.