Number of Americans at risk of man-made earthquakes falls

The number of Americans who live in areas threatened by man-made earthquakes is half of what it was last year, researchers said Wednesday. 

According to a United States Geological Survey report, 3.5 million people live or work in parts of the country where there is “significant potential for damaging shaking” from earthquakes induced by human activity. 

Most of those people live in Oklahoma and southern Kansas, according to the report. 

Last year, the USGS determined that 7 million Americans live in areas threatened by induced seismic activity. 

{mosads}Researchers have blamed the increase in man-made quakes on the injection of wastewater from oil and gas drilling operations into the ground. The high-pressured injection of those fluids into the ground can weaken fault lines and trigger quakes.

The problem is severe enough that regulators in several states with hydraulic fracturing operations have put strict new standards on wastewater disposal there. The USGS said the new regulations — combined with decreased oil and gas production — have lessened the threat of new man-made earthquakes around the country.  

Even so, officials warned that the possibility for earthquakes is still there. 

“The forecast for induced and natural earthquakes in 2017 is hundreds of times higher than before induced seismicity rates rapidly increased around 2008,” said Mark Petersen, the chief of the USGS National Seismic Hazard Mapping Project. 

“Millions still face a significant chance of experiencing damaging earthquakes, and this could increase or decrease with industry practices, which are difficult to anticipate.” 

The USGS began distinguishing between natural and man-made quakes last year following the jump in the seismic activity.

—Updated at 5:21 p.m.