According to the new study published in the journal Science November 17, seismic activity in northwest Alberta over the last five years was likely caused by fracking, a process in which chemically-laden water and sand are injected into shale formations under high pressure to release oil or gas.
Researchers mapped out over 900 seismic events that occurred near the Duvernay shale deposit around the Fox Creek and Duncan Canyon area, dating back to December 2014. This includes the 4.8 magnitude earthquake that occurred on January 12, in Northern Alberta that was considered to be the strongest fracking-induced earthquake ever, reports EcoWatch.
Under current rules, according to CBC News, if an earthquake in the Fox Creek area is a 4.0 magnitude or above, operations must be ceased immediately. Repsol did just that after the January earthquake.
The study found there were two main causes for the earthquakes. The first is the immediate pressure increases as the fracking process is occurring. “We were able to show that what was driving that was very small changes in stress within the Earth that were produced by the hydraulic fracturing operations,” said David Eaton, co-author of the study, reports DeSmogBlog.
The second cause comes from pressure changes created by lingering fracking fluids. A fault will shake when the fluids seep into tiny spaces in the porous rock, causing increased pore pressure.
“If that pressure increases, it can have an effect on the frictional characteristics of faults,” Eaton told the Globe and Mail. “It can effectively jack open a fault if the pore pressure increases within the fault itself and make it easier for a slip to initiate.”
It should be noted that the link to fracturing and earthquakes in Alberta is not related to the recent number of induced earthquakes that occurred in Oklahoma and other western states recently. These earthquakes were likely caused by the injection of large volumes of oil and gas wastewater deep into the underground wells.
“The key message is that the primary cause of injection-induced seismicity in Western Canada is different from the central United States,” Eaton told the New York Times.
