Hydraulic fracturing, commonly known as “fracking,” is a process where shale and other types of impermeable rock are blasted open with water, “fracking fluid” and sand in order to access and extract oil and natural gas.
According to the Natural Resources Defense Council, fracking fluid contains chemical additives, the identities of which have often been shielded from disclosure on the basis that they are “confidential business information” or trade secrets. However, the U.S. Environmental Protection Agency identified 1,084 different reported chemicals used in fracking from 2005 to 2013. Some of the common ingredients found in fracking fluid were ethylene glycol, propargyl alcohol and methanol, all of which are considered hazardous to human health.
Oil and gas operations like fracking also release toxic air contaminants such as benzene, fine particulate matter, hydrogen sulfide and silica dust.
In addition to the chemical cocktails polluting our air and water from fracking, this destructive method of searching for the fossil fuels that are driving the climate crisis has also been shown to cause earthquakes.
New research from scientists at the University of California, Riverside (UC Riverside) confirms that fracking leads to small, slow earthquakes or tremors, the origin of which had previously been unknown.
The study, “Tremor signals during fluid injection are generated by fault slip,” was published in the journal Science.
In the study, the research team looked at data from fracking performed using liquid carbon dioxide, rather than the usual wastewater, reported UC Riverside News. Abhijit Ghosh, associate professor of geophysics at UC Riverside and co-author of the study, pointed out that, since the carbon dioxide is a liquid, the study’s result would almost definitely apply to water-based fracking.
Seismographs record large earthquakes with high amplitude pulses due to their sharp jolts, while tremors appear as slow, gentle rises with less amplitude that gradually decrease.
“We are pleased that we are now able to use these tremors to track the movement of fluids from fracking and monitor the movement of faults resulting from the fluid injections,” Ghosh said, as reported by UC Riverside News.
Earlier debates between seismologists regarding the origin of the tremor signals included theories that they were caused by large earthquakes that occurred far away, while others surmised they were caused by noise from human activity, such as industrial machinery or passing trains.
“Seismometers are not smart. You could drive a truck nearby, or kick one with your foot, and it would record that vibration,” Ghosh said. “That’s why for some time we didn’t know for sure if the signals were related to the fluid injections.”
To try and find the cause of the tremors, the researchers used seismometers around a Wellington, Kansas, fracking site, recording data during the six month fracking injection period, as well as one month before and after.
“We studied seismic tremor signals in Wellington Field, Kansas, using a seismic array during a carbon dioxide injection program. We show that these signals are generated below the surface during the time of carbon dioxide injection,” the authors of the study wrote.
The research team found that the signals leftover, after background noise was discarded, came from underground and only appeared during fluid injections.
“We did not detect the tremors before or after the injections, which suggests the tremors are related to them,” Ghosh explained, as UC Riverside News reported.
Stopping the toxic and dangerous practice would be one way to prevent faults from slipping and producing tremors and the larger earthquakes that fracking has been known to cause. Ghosh said that, since that is unlikely to happen, monitoring the activities in order to understand how they are deforming rocks, as well as tracking fluid movement after fracking injections, is important.
Companies perform model experiments to determine what the limits for fluid injection pressures should be, according to UC Riverside News. Adhering to the established limits helps keep fluids from migrating in the direction of large underground faults that could trigger seismic activity.
“We can only model this type of experiment when we know there is an existing fault. It is possible there are faults we do not know of, and in those cases, we cannot forecast what will happen,” Ghosh said, as reported by UC Riverside News.