This article examines a possible link between hydraulic fracturing (HF) operations and the earthquakes recorded in the St. Lawrence Valley (SLV) between Montreal and Quebec City, Quebec, Canada. Between November 2006 and July 2010, HF operations were conducted in 18 different wells to evaluate the shale gas potential of the local Utica shales.
For earthquakes between years 2006 and 2012, we considered the distances between the HF wells and the epicenters and the time differences between the end of HF activity and the origin times of earthquakes. In addition, Rayleigh (Rg) phases were interpreted as an indicator of a shallow source. It was found that only three shallow focus earthquakes were within 15 km of HF wells. Shallow tectonic earthquakes are rare occurrences in the SLV (5% of cases), but a shallow source does not necessarily indicates that the event was induced by HF operations. The time interval between the end of HF operations and the occurrence of these earthquakes varied between 298 (0.81 yr) and 1348 days (3.75 yrs), making a connection very unlikely, especially when the small cumulative volume of fluids that was injected is considered. In conclusion, the HF operations in the SLV were not connected to any detectable induced seismicity (IS).