Examination of Shallow Structure in Geothermal Sites of Western Canada Using Microtremor Measurements: Mount Meager and Burwash Landing Case Studies
Date
2024-02-15
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Abstract
Canada has enormous geothermal potential, a sustainable alternative energy in the form of heat. Despite its significant role in moving Canada closer to net-zero CO2 goals, geothermal resource production faces numerous exploration challenges, notably the risks associated with drilling. However, with the emergence of new technologies, e.g., closed-loop systems and declining costs, geothermal energy is increasingly competing with conventional resources like coal. This thesis investigates the use of the Horizontal-to-Vertical Spectral Ratio (HVSR) method, also known as Nakamura’s method or microtremor HVSR (mHVSR), in two geothermal exploration projects. Commonly referred to as HVSR in the geophysical community, this method analyzes microtremors and is effective in determining seismic structures up to 200 meters deep at Mount Meager and 500 meters at Burwash Landing. HVSR complements other geophysical methods that focus on deeper structures and overcomes the limitations of surface geology. At Mount Meager, British Columbia, HVSR has been instrumental in identifying resonance frequencies and understanding the subsurface structure. It has revealed the variability in the shallow subsurface, aiding in the estimation of volcanic unit thicknesses and expanding upon existing geological and seismic data. This has enhanced the understanding of subsurface geology and associated risks. In Burwash Landing, Yukon Territory, where geothermal energy is crucial for local energy needs, the application of a trans-dimensional Bayesian inversion algorithm on HVSR curves has provided detailed insights into seismic structures. This method has offered accurate estimations of bedrock depth and sediment compaction, refining previous interpretations. Notably, it helped correct overestimated sediment layer thicknesses encountered during a drilling operation in November 2022. The trans-dimensional approach avoids the use of predefined models, quantifies uncertainty, and adds objectivity to interpretations. Overall, these studies highlight the importance of HVSR in geothermal exploration, especially in areas with complex topography and geology. HVSR is crucial for understanding shallow structures, assessing associated hazards, and informing studies on deeper geothermal resources. The findings significantly contribute to the understanding of seismic structures in these regions, with broader implications for global sustainability, energy self-sufficiency, and environmental objectives.
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Keywords
Horizontal-to-Vertical Spectral Ratio (HVSR), geothermal, Bayesian inversion, Mount Meager, Burwash Landing
Citation
Berumen Borrego, F. (2024). Examination of shallow structure in geothermal sites of Western Canada using microtremor measurements: Mount Meager and Burwash Landing case studies (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.