Exposure and vulnerability for seismic risk evaluations

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

Earthquake Damage Data Collection Using Omnidirectional Imagery

The unique perspectives and viewpoints offered by omnidirectional camera technology has the potential to help improve the outcomes of technical post-earthquake reconnaissance missions. Omnidirectional imagery can be used to virtually “walk through” damaged streets post hoc with a 360°, immersive view. A common reconnaissance mission aim is to accurately collect damage data; however, there are time challenges for surveyors in the field. The manuscript explores the potential for using omnidirectional imagery to improve damage surveying, firstly by comparing results from damage surveys completed in the field with results obtained using omnidirectional images collected during a mission and surveyed by an experienced engineer virtually and secondly by comparing damage assessment obtained through omnidirectional imagery collected on the ground with the EU Copernicus damage assessment maps. The omnidirectional imagery data was collected during two separate Earthquake Engineering Field Investigation Team post-earthquake reconnaissance missions, namely the area affected by the 2016, 7.8 Muisne Earthquake in Ecuador and the area struck by the 2016, 6.2 Amatrice earthquake in Italy. Notwithstanding the diverse geographic scale, terrain and urban context of the two reconnaissance missions, the results consistently show significant capabilities for this technology in the identification of construction typologies, number of stories, aggregated “low” and “high” damage grades, and failure modes. The work highlights potential issues with correct identification of disaggregated lower damage grades (e.g., European Macroseismic Scale (EMS-98) damage grades 0–3). Challenges identified in the virtual survey process included poor image quality, insufficient photo sphere captures, and obstructions such as trees, walls or vehicles. The omnidirectional imagery represents a substantial improvement in damage assessment accuracy in respect to satellite imagery, especially for lower damage grades, while it is an essential tool for comprehensive surveys in reduced access zones with high levels of damage

Historical Trajectories of Disaster Risk in Dominica

The calamitous consequences of 2017 Hurricane Maria for the Caribbean island of Dominica highlighted the acute and increasing susceptibility of the region to disasters. Despite increasing international attention to disaster risk reduction, recovery from hazard events can be especially lengthy and difficult for small island developing states. In this article, we build on existing understandings of disaster risk as a physical and social condition, showing that historical processes are fundamental to understanding how conditions of risk emerge and persist over time. We take an integrated approach to analyzing the drivers of risk accumulation, using the example of Dominica, where processes set in motion during the colonial period have shaped the location of people and assets, the degree to which they might be harmed, the societal repercussions of that harm and the prospects for recovery. We focus on the underlying economic vulnerabilities and physical exposure to hazards created by agricultural, economic, and social practices, and successive disaster responses that have constrained recovery. Uncovering these historical drivers and persistent issues, elucidates lessons for pursuing a more resilient development trajectory, including through the promotion of economic restructuring and diversification, and land reform

The April 2016 Muisne (Ecuador) Earthquake : Behaviour of Low-rise RC Frames with Masonry Infill, and Recommendations for New Construction

The 16th April 2016 Mw 7.8 Muisne earthquake in Ecuador caused nearly 700 fatalities, 230,000 injuries and over 35,000 damaged or collapsed homes, leaving 140,000 without adequate housing. The majority of the damaged structures, in particular in urban and peri-urban areas, were constructed from low-rise reinforced concrete frames with unreinforced masonry infill. It was evident by their design that these buildings are generally non-engineered, or at least not correctly engineered, for seismic loads. This paper draws on observations made primarily from the EEFIT reconnaissance mission, augmented from other missions to the affected region, to describe the typical types of damage and failures seen in this building taxonomy, and why these are likely to have occurred. The paper then explores confined masonry as an option for new construction. An example is presented of the successful implementation of confined masonry post-event in the affected region, describing the approach that was adopted, in particular training, promotion and dissemination of the confined masonry technique, as well as the challenges of influencing people’s existing perceptions and styles. The paper concludes with a summary of why confined masonry is considered to be a durable, resilient, easy to construct and appropriate form of new construction in Ecuador.Applied Science, Faculty ofNon UBCCivil Engineering, Department ofUnreviewedFacultyResearcherOthe