Small earthquakes linked to underground wastewater injection are substantially weaker in their effects than natural earthquakes of the same magnitude, according to a new study conducted by the U.S. Geological Survey . Natural earthquakes are approximately 16 times as strong as human-induced tremors of the same magnitude.
Recent Increase in Small Quakes
The USGS has documented an increase in small earthquakes in the central and eastern United States in recent years, with evidence indicating a likely link to underground wastewater disposal. Energy producers often inject wastewater from the hydraulic fracturing (also known as fracking) process underground after extracting oil and natural gas via hydraulic fracturing. Although the fracking process itself appears to have no effect on seismic activity, re-injecting wastewater after the completion of fracking operations can in some instances cause minor earthquake tremors.
No wastewater injection tremor has caused loss of life, serious injury, or property damage, and most cannot even be felt by humans. Even so, scientists are studying wastewater-induced tremors to assess the safety of the practice.
‘Wimpy’ Manmade Tremors
In the new USGS study, geophysicist Susan Hough studied similar-sized natural and wastewater-induced tremors. Although one might expect tremors of the same seismic magnitude would be felt similarly, Hough discovered the wastewater-induced tremors produced much weaker effects. Magnitude 4.8 wastewater-induced tremors, for example, felt like magnitude 4.0 natural tremors.
“It turns out there’s a big difference between these induced earthquakes and natural earthquakes,” said Hough in a press statement.
“These induced quakes are essentially wimpy in terms of the shaking they’re creating,” Hough added.
Hough’s study is scheduled for publication in the Bulletin of the Seismological Society of America.
Fracking’s Impressive Safety Record
Heartland Institute Science Director Jay Lehr, who received the nation’s first Ph.D. in groundwater hydrology, says the findings confirm the environmental safety of hydraulic fracturing.
“Despite what you hear from the anti-fracking community, hydraulic fracturing has never been shown to cause any earthquakes, no matter how small. To the extent that re-injecting wastewater underground after the hydraulic fracturing process may cause some occasional small tremors, those tremors have never caused injury or property damage. They are simply too small to be significant,” said Lehr.
Lehr noted energy producers have utilized fracking methods since the mid-twentieth century with an impeccable environmental safety record.
“Hydraulic fracturing has passed a whole gamut of environmental tests with flying colors,” Lehr said. “If the minor tremors apparently caused by wastewater re-injection ever proved to be a serious risk, the answer would be to reassess the wastewater re-injection process rather than the hydraulic fracturing process.”
James M. Taylor ([email protected]) is senior fellow for environment policy at The Heartland Institute.