Why some earthquakes caused by fracking come with warning signs
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.
Fracking, a process involving high-pressure fluid injection to fracture rock and release oil or gas, can trigger earthquakes. However, the occurrence of foreshocks—small tremors preceding the main earthquake—varies greatly depending on the location. An international research team analyzed seismic records from western Canada between 2014 and 2024, identifying 77 magnitude 3 or larger earthquakes linked to hydraulic fracturing.
Eighty-one percent of these events were preceded by smaller tremors within 5 kilometers and five days prior to the main event. While fluid injection rates cannot fully explain these differences, local fault conditions play a significant role. Faults that are more sensitive to injected fluids and closer to failure tend to experience more foreshocks.
This variability means that large earthquakes can sometimes strike with little warning, challenging current safety protocols. The study suggests that traffic-light safety systems should be adapted based on local geology, incorporating seismogenic susceptibility, real-time seismic-geodetic observations, and physics-based nucleation models.
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