Want to find out where the riskiest places in the United States are for human-caused earthquakes? The government has you covered.
The United States Geological Survey released maps Monday that, for the first time, illustrate the risk of both natural and human-induced earthquakes throughout the eastern and midwestern United States. Human-caused earthquakes are, in many cases, triggered by the oil and gas production process — studies have linked hydraulic fracturing and wastewater disposal to earthquakes in multiple states.
Six states are particularly at risk from human-caused earthquakes, according to the USGS: Oklahoma (the state USGS says faces the most risk), Kansas, Texas, Colorado, New Mexico, and Arkansas. About 7 million people total live in eastern and central regions of the United States that are at risk from these earthquakes, according to USGS researchers, who looked at earthquake logs in these regions in order to create the maps.
“By including human-induced events, our assessment of earthquake hazards has significantly increased in parts of the U.S.,” Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project, said in a statement. “This research also shows that much more of the nation faces a significant chance of having damaging earthquakes over the next year, whether natural or human-induced.”
Typically, human-induced earthquakes are caused by the injection of fracking wastewater deep underground. This water can cause the earth’s faults to slip, triggering an earthquake. Scientists have also tied fracking itself — the act of injecting water, chemicals, and sand underground at high pressures to crack open shale rock and access the gas trapped within — to earthquakes, including earthquakes strong enough to be felt by humans. Researchers on the call said that the science is basically settled on whether wastewater disposal can cause earthquakes.
“I think there’s consensus within the scientific community,” and close to a consensus among energy companies, that wastewater injection can cause earthquakes, said Justin Rubinstein, deputy chief of USGS’ Induced Seismicity Project, on the call. There may be arguments over how specific earthquakes formed, but in general, wastewater injection causing earthquakes is a well-known phenomenon.
The USGS didn’t look at the western U.S. for these maps, in part because since many West Coast states already deal with natural earthquakes on a regular basis, human-caused earthquakes didn’t significantly change earthquake risk in those regions.
“That’s not at all the case in the central and eastern U.S.,” said Michael Blanpied, associate coordinator of the Earthquake Hazards Program, on a call Monday. In these states, earthquake risk is “dramatically different” than it was in 2009, he said.
As the maps show, Oklahoma has been hit particularly hard by human-caused earthquakes. From 1991 to 2008, Oklahoma saw three or fewer 3.0 magnitude — the magnitude at which an earthquake can be felt “quite noticeably” by people — or higher earthquakes each year. Since 2009, the state has seen a drastic increase in earthquakes, both above and below magnitude 3.0. In 2014, the state was the most seismically active among all lower 48 states. That year, the state saw 585 earthquakes — a number that soared in 2015, when the state saw 857 earthquakes.
These earthquakes have sparked multiple lawsuits in the state: in January, a group of 14 Oklahoma homeowners filed a lawsuit against 12 energy companies, claiming the companies’ oil and gas operations are causing dangerous earthquakes. Another lawsuit is trying to get class-action status for residents in nine Oklahoma counties, all of whom claim their homes have been damaged by human-induced earthquakes.
The USGS, as an information agency, did not make any policy recommendations from the research. But USGS scientists said on the call that they hope the maps help residents and policy-makers better understand the risk human-caused earthquakes.
“Many communities in California have faced this problem of seismic hazard and have taken steps” to strengthen or remove buildings, Blanpied said. “Earthquake hazard is a relatively new thing for central communities in the U.S., so hopefully people will find this report useful in starting to look at this hazard.”