| Abstract: | First observations of geologically young rock faults and folds in New York in the late nineteenth century were shortly followed by others in Ontario. Remapping of the Paleozoic rocks began in the 1930s, and Quaternary geology mapping became organized in the 1950s, leading to further discoveries of faults and folds in the bedrock. Engineering works in the Niagara and Hamilton areas from the 1890s to the 1970s encountered repeated problems of rock squeeze. The separate geological and engineering experiences were linked in the 1970s, and with heightened awareness, discoveries of rock disturbances (mainly popups) greatly increased in the 1970s and 1980s. Understanding centered on high horizontal stress in the bedrock, which became quantified through rock testing and modeling. The creation of the Multi-Agency Group for Neotectonics in Eastern Canada (MAGNEC) in 1986 brought together a diverse group interested in all aspects of neotectonics, including the distribution and causes of rock stress and the potential implications for seismic risk. The existence of nuclear power plants sensitive to variations in the stress environment and high population densities near the Great Lakes provided motivation for further attention, and Prince Edward County was designated for special study. Recent suggestions of reduced seismic activity under ice sheets and increased activity associated with isostatic uplift during their retreat lead to the question whether seismic risk is slowly decreasing as uplift rates decline. |
