Wuorinen, Val2024-08-152024-08-1519741974https://hdl.handle.net/1828/20209Earthquakes represent the most serious catastrophic natural hazard in the Victoria area. The city is in Zone 3, the highest Canadian risk category, and an earthquake capable of generating intensity VIII on the Modified Mercalli Scale is postulated with a return period of one hundred years. However, because of differences in local ground conditions, the actual intensity of shaking during an earthquake may be expected to vary considerably. A seismic microzonation map showing this anticipated spatial variation in intensity is obviously required to enable decision makers to evaluate possible alternatives in reducing the harmful effects of future earthquakes. This study aims to provide such a microzonation of the city of Victoria. It is based on a geomorphological, investigation of local bedrock topography and Quaternary stratigraphy, and includes an intensity survey of the last earthquake, occurring in 1946, which caused extensive damage in the city. From a study of borehole data, city engineering reports, pre-development maps, and fieldwork, a three dimensional overview of the city's geomorphology was obtained and mapped. By interviewing persons who had been in Victoria during the 1946 earthquake, over two hundred intensity ratings for that event, ranging from III to VII, were obtained. An attempt was then made to explain the spatial variations in intensity by correlation with possible causal variables. A strong correlation was found to occur between intensity experienced and round conditions, so providing the basis for the development of a three-zone microzonation map of Victoria. On this model, intensities lower than average can be expected in areas where bedrock appears within ten feet of the surface, while in contrast higher than average intensities are anticipated in areas underlain by thick Victoria clay. Over one-half of Victoria falls into the first category, while only small areas of unfavourable ground have been identified. At present, the only human adjustments to the seismic hazard in Victoria appear to be the application of earthquake-resistant building regulations to major structures and individual insurance policies. It is hoped­ that the microzonation map included in this study may serve to heighten the perception of risk and so stimulate a greater range of social adjustments.156 pagesAvailable to the World Wide WebThesis