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Field and remote sensed first-order approaches towards Empirical seismic vulnerability assessment of unreinforced masonry buildings
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  • Thando Nqasha,
  • Mulemwa Akombelwa,
  • Zeenath Khoyratty,
  • Mayshree Singh,
  • Andrzej Kijko
Thando Nqasha
University of KwaZulu-Natal

Corresponding Author:[email protected]

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Mulemwa Akombelwa
University of KwaZulu-Natal
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Zeenath Khoyratty
University of KwaZulu-Natal
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Mayshree Singh
Maya geophysics
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Andrzej Kijko
University of Pretoria
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Abstract

The 5 August 2014 Orkney earthquake in South Africa caused significant damage to low-cost unreinforced masonry buildings. After the earthquake, post-earthquake surveys were conducted to assess damage and deduce intensity of these buildings. During the field surveys, only buildings that were reported as damaged were investigated. This study aimed at conducting an empirical seismic vulnerability assessment using data collected from field surveys. However, for a comprehensive assessment, the data should include all buildings in the study area, regardless of whether they were damaged or undamaged. Hence in this study, a first-order approach was applied to gather sufficient data to construct fragility curves for low-cost unreinforced masonry buildings in South Africa. The damage probability matrix technique was selected from the available empirical seismic assessment procedures for fragility curve construction. The fragility curves were constructed using the intensity and damage data, statistical models, and model fitting techniques. Damage and intensity were measured using the European macro-seismic scale. The fragility curves obtained in this study predicted comparable but slightly lower damage compared to other curves of unreinforced masonry buildings of similar typology. These curves were obtained for URM buildings that were damaged during the 2017 Iran-Iraq earthquake that occurred along the in the Zagros fold and thrust belt; the 2009 L’Aquila earthquake; and the 1962 and 1969 Sarajevo and Banja Luka earthquakes. The reason for predicted lower damage might be due to the fact that majority of buildings in the study were assumed to have no damage. Even though the method applied was able to produce comparable fragility curves with other studies, it is recommended that during the post-earthquake surveys, all the buildings in the study area should be investigated including those that suffered little to no damage in order to get a good sample of buildings vulnerability.