According to a press release by Ruhr-Universität-Bochum, a research team; A new type of earthquake has been detected in an area in British Columbia, Canada. With a network of eight seismic stations surrounding an injection well a few kilometers away, researchers from the Geological Survey of Canada, Ruhr-Universität Bochum and McGill University recorded seismic data from nearly 350 earthquakes. It has been observed that approximately 10% of the earthquakes detected in the recorded data exhibit similar characteristics to earthquakes experienced in volcanic areas, such as breaking more slowly.
It was noted that the new type of earthquake, unlike other earthquakes of the same magnitude, occurred more slowly and lasted longer than normal. It was stated that the earthquake was triggered by hydraulic fracturing, a method used to extract oil and gas in western Canada.
New type of earthquake an ‘intermediate form’ of seismic shear with conventional earthquakes
Until now, experts had explained the earthquakes that occurred during hydraulic fracturing with two different processes. According to the first of these, the liquid pumped into the rock causes a pressure large enough to create a new crack in the underground rock near the well.
With the increasing pressure, a large amount of accumulated energy is released that can trigger an earthquake by affecting the existing faults. According to the second explanation, the liquid pressure increase caused by underground injection causes elastic stress changes that are effective at longer distances on the surrounding rocks, and if these changes occur in the rocks where the faults are located, an earthquake can be triggered.
More recently, numerical models and laboratory analyzes have concluded that the same process observed on tectonic faults elsewhere also occurs on faults near injection wells. This process, which starts as a slow slip that does not release any seismic energy and is called ‘seismic slip’; It can also cause rapid shifts on nearby faults and changes that cause earthquakes.
However, the lack of seismic energy resulting from seismic shift and the size of the faults in question can make this phenomenon very difficult to observe in nature. For this reason, researchers have not yet been able to concretely document a link between triggered earthquakes and seismic shifts. However, the research team interprets these recently discovered new slow earthquakes as an intermediate form of traditional earthquake and seismic slip, and thus indirect evidence that seismic slip can also occur near wells. That’s why the researchers call the new type hybrid frequency waveform earthquakes (EHWs).
“We assumed that triggered earthquakes behave like most other earthquakes and have roughly the same breaking rate, two to three kilometers per second,” said research team member Rebecca Harrington, which isn’t actually the case. According to the data recorded by the researchers, the shaking from a conventional 1.5-magnitude earthquake ceases after about seven seconds, while an EHW earthquake of the same magnitude continues to shake for more than ten seconds. It is speculated that the discovery could help minimize the damage caused by the tremors triggered by the fracture.
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