Thesis Format

Monograph

Evaluation of Effectiveness in Seismic Microzonation Hazard Mapping in Canada: Communication, Use, Standardization and Levels

Author

Meredith L. Fyfe, Western UniversityFollow

Degree

Master of Science

Program

Geophysics

Collaborative Specialization

Environment and Sustainability

Supervisor

Molnar, Sheri

Abstract

Comprehensive seismic hazard maps in the form of seismic microzonation maps have been produced for many populous and seismically active Canadian cities. These maps are important tools for regional decision making for technical (engineering) and non-technical (planning, emergency management, insurance) applications. Outcomes from stakeholder engagement indicate that non-technical end users are not confident in their interpretation of the maps or the mapped site effect predictors (metrics). Users may seek seismic hazard information from lower-level mappings, such as the global Vs₃₀ mosaic, which, when compared against the higher-level Canadian mappings, was found to correctly estimate site class with 26% accuracy and Vs₃₀ values within ±49% of in situ measurements. Implementing best practices in cartographic design, using metrics consistent with building codes, distributing maps in digital formats, and co-developing products with end users are suggested to improve user comprehension and support effective utilization of higher-level Canadian seismic hazard products for regional applications.

Summary for Lay Audience

Many populous cities are located in earthquake prone regions and so we prepare for earthquakes by designing buildings and preparing emergency management strategies based on knowledge of a region’s seismic hazard. A key element of that hazard is the strength of ground shaking, which depends on the earthquake’s magnitude, its distance, and local site conditions, such as geology and topography. Sites with different conditions may respond differently in an earthquake, and this spatial variability of site conditions across a region is mapped to display relative seismic hazard as a region-specific seismic hazard map. Not only may several maps be generated and available with differing levels of detail and thereby accuracy for a given region, but many users of these maps, who are not technical experts in seismic hazard, may be challenged to understand what the maps are communicating or to determine which map is appropriate or suitably accurate for their intended application. Canadian end users’ comprehension of seismic hazard measures or metrics and their interpretation of mapped products was evaluated in this thesis during a regional stakeholder engagement workshop as well as from a nation-wide online questionnaire survey to determine how seismic hazard maps should be improved to communicate technical information more effectively. Further, higher accuracy seismic hazard maps for six urban centres in Canada were compared with lower accuracy global-scale mapping to evaluate the difference between these two different levels of available region-specific seismic hazard maps. Outcomes of these investigations were used to inform a set of best-practice recommendations for producing future region-specific seismic hazard maps in Canada and to promote the use of the more detailed type of maps, where available, for regional-scale decision making. Where comprehensive region-specific seismic hazard maps are not yet available in Canada, maps of lower detail may be used but should consider their error (approx. 30-50% depending on the chosen metric) compared to more detailed and higher accuracy mapping demonstrated in this thesis. Ultimately, better informed decision makers make better decisions, and producing and using effective region-specific seismic hazard maps are important factors for improving society’s earthquake resilience.

Recommended Citation

Fyfe, Meredith L., "Evaluation of Effectiveness in Seismic Microzonation Hazard Mapping in Canada: Communication, Use, Standardization and Levels" (2023). Electronic Thesis and Dissertation Repository. 9567.
https://ir.lib.uwo.ca/etd/9567