Scenario-based earthquake risk assessment for central-southern Malawi: The case of the Bilila-Mtakataka Fault

Abstract

A regional seismic risk analysis for central-southern Malawi is conducted by focusing on the Bilila-Mtakataka Fault within the East African Rift System and by incorporating local information on population exposure and building vulnerability. The scenario-based earthquake risk assessments account for uncertainty in geometry, position, and rupture pattern of the Bilila-Mtakataka Fault as well as ground-motion variability and are based on the latest 2018 national census data. In addition, Malawi-specific seismic fragility functions, which were developed based on building surveys and laboratory tests of local construction materials, are implemented to reflect realistic seismic vulnerability of unreinforced masonry constructions in Malawi. The results from the earthquake risk assessments and sensitivity analyses based on alternative data and models highlight the importance of incorporating local information on seismic hazard characterisation, population data, and seismic vulnerability of buildings, in comparison with global data and models. For the considered case study region, individual effects of the above-mentioned model components tend to result in 20–30 % or greater differences in regional seismic risk metrics, such as the affected population experiencing a certain ground shaking intensity level or the number of collapsed housing units. The improved seismic hazard-risk assessments are more effective in informing future seismic risk mitigation policies and actions.