Exposure and vulnerability for seismic risk evaluations

• Main Author: Stone, Harriette
• Other Authors: D'Ayala, D. ; Gunasekera, R. ; Rossetto, T.
• Published: University College London (University of London) 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.756118

To make effective decisions for earthquake risk reduction, accurate seismic risk evaluations are required. Substantial data, methods, and tools from the field of structural engineering are used in the seismic risk assessment process, including the collection and interpretation of building data and the estimation of seismic vulnerability, for which there are numerous sources of inefficiency and inaccuracy. Compiling building exposure datasets in an effective manner for use in seismic vulnerability and risk assessments requires methods that collect applicable or useful data whilst balancing accuracy and cost. This thesis investigates this three-way balance. First, a systematic review of the literature is completed to ascertain the most useful building data for estimating seismic vulnerability. Useful building characteristics are determined by: (1) investigating the frequency of building characteristics used in published seismic vulnerability assessment methods, and (2) reviewing studies that explore the sensitivity of inputs to vulnerability assessments; the more sensitive the input, the more useful the data. Second, a range of building data collection methods are tested in the urban centre of Guatemala City. A series of desk-based studies are used to collate published and available information, such as housing censuses, existing studies, the history of urban development, and construction practices and trends. Field-based methods are then employed including established methods such as street-level rapid visual surveys and detailed internal surveys, and newer methods such as virtual surveys using omnidirectional imagery and three-dimensional models derived from unmanned aerial vehicle imagery. The resources required by each method are calculated from the actual costs encountered in the desk study, fieldwork, and post-trip analysis. The accuracy of collected data is determined by justifying assumptions of accurate data and comparing results for individual buildings across the methods using inter-rater agreement statistical methods. The balance of data usefulness, cost and accuracy is examined in detail to highlight the effectiveness of the tested data collection methods. It is found that the building data collection methods that employ newer technology have great potential in this field, although some struggle to collect all of the necessary data to classify building typologies and assess seismic vulnerability, so are most effective when combined with other datasets. Using the collected data, the seismic vulnerability and risk of the study area are estimated, and a preliminary study starts to investigate the impacts of uncertainties in building data when propagated through to loss ratios. Further work is required, but the preliminary result indicate that range the in losses is significant, highlighting the need for accurate building data collection to feed into seismic exposure and vulnerability assessments and, in turn, seismic risk evaluations.