This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Fracking, the injection of high-pressure fluid to fracture rock and release oil or gas, can trigger earthquakes. While some sites generate small tremors beforehand that may provide an early warning, others produce few or none.
An international research team set out to discover why these foreshock patterns vary so dramatically and what this means for current safety protocols designed to reduce earthquake risks. To investigate how common foreshocks are, the scientists analyzed seismic records across western Canada from 2014 to 2024. They built a catalog of roughly 70,000 earthquakes and identified 77 magnitude 3 or larger quakes associated with hydraulic fracturing.
Next, they analyzed seismic data alongside fluid injection records, satellite measurements of ground deformation, and other geological and geophysical data for these events. Their findings are published in the journal Science. The team discovered that 71 of the 77 magnitude 3 or larger events were preceded by smaller tremors within 5 kilometers (3 miles) in the five days leading up to the main event.
"Foreshocks are pervasive before ML ≥ 3 induced mainshocks in western Canada," wrote the study authors. But the number of foreshocks varied wildly. While one quake was preceded by more than 700 small tremors, six events struck with no foreshocks within this five-day, 5-kilometer (3-mile) window.
Injection factors, such as how fast or how much fluid was pumped into the ground, could not fully explain these dramatic differences on their own. "Injection is necessary but insufficient to explain foreshock productivity." Instead, the number of foreshocks was also linked to local fault conditions. Sites with lots of foreshocks tended to be located in areas where underground faults were most sensitive to injected fluids and showed signs of being close to failure.
By contrast, less sensitive fault zones that lacked these signs tended to produce few or no foreshocks. This means a larger induced earthquake could strike with little to no advance notice from seismic monitoring. After studying ground deformation and seismic patterns, the scientists concluded that fluid injection can push faults toward a larger earthquake in three ways.
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