The number of people at risk for earthquake damage brought on by oil and gas activity is expected to plummet this year, thanks to state regulations as well as market forces, according to a federal forecast released Wednesday.
The U.S. Geological Survey’s 2017 report on earthquakes predicted that about 3.5 million people face significant potential for damage from induced earthquakes, a sharp decline from the 2016 forecast of about 7 million.
Most of those at risk in 2017 from potentially hazardous human-caused earthquakes live in Oklahoma and southern Kansas.
“The story is generally good news in terms of potential damage from induced or man-made earthquakes,” Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project, said in a press call. “Generally, the chance of damage is decreased.”
Mr. Petersen chalked up the earthquake decreases to “regulatory actions by state officials starting about 2014, when they restricted injections and closed some wells, but it’s also potentially related to the declining price of oil, which reduced injected volumes of wastewater.”
The report published Wednesday in Seismological Research Letters also found that the number of “felt earthquakes,” or those above magnitude 2.7, declined in 2016. Earthquakes below magnitude 2.7 are typically detectable only by instruments.
The number of tremors in Oklahoma dropped from 4,000 in 2015 to 2,500 in 2016. Most of those registered below magnitude 2.7, but the state also experienced for the first time three earthquakes of magnitude 5.0 or above.
Any earthquake above magnitude 4.0 has the potential to cause damage to plaster or unreinforced masonry.
“These reductions in earthquake rates indicate that this type of seismicity is manageable or controllable, which is great news,” Mr. Petersen said.
“The bad news is that during the past year, Oklahomans experienced the most active periods for large-magnitude 5.0-plus earthquakes in their recorded history,” he said.
The Sept. 3 magnitude 5.8 tremor near Pawnee, Oklahoma, was the largest recorded in the state’s history.
The surge in ground shaking in the central United States, brought about by the oil and gas boom, has fueled calls for a ban on hydraulic fracturing, but the quakes are not caused by fracking in most cases, according to the USGS.
Rather, the agency attributes the shaking to the injection deep into the ground of wastewater (which is produced even at unfracked oil wells) increasing pressure on fault lines in some instances.
Katie Brown, a spokeswoman for Energy in Depth, a project of the Independent Petroleum Association of America, said the report provides evidence that efforts to reduce ground shaking caused by oil and gas operations are paying off.
“The lower risk of induced seismicity is a clear sign that the collaborative efforts between industry, scientists and regulators are working,” Ms. Brown said in a statement. “In Oklahoma, the number of earthquakes last year dropped by 31 percent, and there were zero felt earthquakes in North Texas in 2016. This study is in line with what numerous experts have said: The risk of induced seismicity is small, rare and manageable.”
In 2016, seismologists recorded no earthquakes of magnitude 4.0 or larger in the “high hazard areas” of north-central Texas and central Arkansas.
“I feel this is a success story in how we can reduce the seismic hazard, and this came about because of persistent and continued efforts between the science and engineering regulatory communities and the media who help us communicate these results,” said Mr. Petersen.
There were only two earthquakes of magnitude 2.7 or larger on average per year in Oklahoma from 1980 to 2000.
The oil-and-gas industry has put Oklahoma on par with California in terms of earthquake activity, although the Golden State’s temblors are largely the result of fault lines such as the San Andreas Fault.
Another half-million people in the central United States are at risk for significant chance of damage from natural earthquakes.
“The forecasted chance of damaging ground shaking in central Oklahoma is similar to that of natural earthquakes in high-hazard areas of California,” the USGS said in a press release.
The USGS began issuing maps and forecasts on both human-caused and natural earthquake activity last year.
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