A study by the Alberta Geological Survey has concluded the cause of the earthquake that rocked Sylvan Lake in March, 2019.
According to a report published by the Alberta Geological Society, a department of Alberta Energy Regulators (AER), the earthquake was caused by fracking at a nearby site.
The report, released last month, details finding from the ML4.18 earthquake with the epicentre located about 12 kilometres south of town, as well as ML 3.13 quake a year prior located near Red Deer.
The Alberta Energy Regulators deemed the two quakes suspicious, due to their location.
“The observation of these events in a typically seismically quiescent region was suspicious, considering the recent development of the Duvernay East Shale Basin,” the report reads.
Vesta Energy, a Calgary-based company, was fracking at the time and in the vicinity of earthquake.
AER said they had to use information obtained by Vesta Energy to properly assess the situation, and find a cause for the quake.
“Because deployments of seismic monitoring stations in the province have been skewed to more seismically active areas, assessing the induced status of this cluster based solely on data from those areas was impossible. Instead, the operator of the well in question deployed a passive seismic monitoring network to more thoroughly address the issue.”
Vesta Energy has a site near Sylvan Lake and reported it was fracturing at the time of the quake. Operations at the site immediately ceased, according to an AER order.
Director of Environment and Operational Performance Erik Kuleba said in the order issued to Vesta Energy “that a release of a substance or substances has occurred, and that substances have caused, are causing, or may cause an adverse effect.”
Before Vesta Energy was able resume operations, they had to submit a plan to AER by March 11 “to show how they will minimize the risk of any seismic impacts in the future.”
Vesta Energy had to include all passive seismic data from April 2018 to present.
In May, Vesta was able to start working at the site once again. Alberta Energy Regulators said Vesta’s risk assessment plan showed minimal risk of seismic impacts in the future.
According to the AGS, Alberta has experienced more than 600 earthquakes between 1985 and 2011. During the same time, Saskatchewan only experienced 41 recorded earthquakes.
Most of Alberta’s recorded earthquakes are distributed evenly along the foothills and Rocky Mountains, there are also clusters of earthquakes east of the Rocky Mountain “deformation belt” around Rocky Mountain House, according to AGS.
Earthquake seismologists with the Geological Survey of Canada originally believed the cause of the March 4 earthquake.
The original cause was believed to be from tectonic movement along the Rocky Mountains. While Central Alberta is a distance away from a fault line, quakes still occur every few years, as stress from the fault lines can often be felts a ways away.
The quake was relatively centralized. Reports say the shock could be felt in Red Deer, Lacombe, Blackfalds, Eckville, Penhold and as far north as Gull Lake.