The study, led by researchers at the University of Alberta, tested a framework developed by the Alberta Energy Regulator (AER) and a framework developed by the British Columbia Oil and Gas Commission (BCOGC). Both frameworks use a traffic light system to assess the likelihood that an earthquake was induced by human activity, with green indicating a low likelihood, yellow indicating a possible likelihood, and red indicating a high likelihood.
The AER framework assigns a color based on the distance between the earthquake and nearby injection wells, the volume of fluid injected into the wells, and the timing of the earthquake relative to injection activity. The BCOGC framework also considers these factors, but it also includes an assessment of the regional tectonic setting and the presence of other potential earthquake triggers.
The study found that both frameworks classified the Fox Creek earthquake as yellow, indicating a possible likelihood that it was induced. However, the AER framework assigned a higher likelihood of induced seismicity than the BCOGC framework. This difference is likely due to the fact that the AER framework does not consider the regional tectonic setting, which may have contributed to the earthquake.
The study also found that both frameworks are sensitive to the choice of input parameters. For example, the distance between the earthquake and nearby injection wells is a key factor in both frameworks, but the definition of what constitutes a "nearby" well can vary. Similarly, the volume of fluid injected into wells is a factor in both frameworks, but the exact cutoff value for classifying a well as "high-volume" can vary.
The study concludes that while the AER and BCOGC frameworks provide a useful starting point for assessing the likelihood that an earthquake was induced, they are not foolproof and should be used in conjunction with other methods, such as detailed seismic analysis and modeling.
The Fox Creek earthquake was the largest earthquake to occur in Alberta in over 60 years. It caused significant damage to homes and businesses in the area and raised concerns about the potential for induced seismicity in the province. The AER has since implemented a number of measures to reduce the risk of induced seismicity, including limiting the volume of fluid that can be injected into wells and requiring operators to monitor seismic activity near their operations.
