For the first time, the U.S. Geological Survey is pinpointing the places where quakes induced by human activity as well as natural seismicity are most likely to occur this year.
The map released today dramatically raises the earthquake risk assessment for areas of Oklahoma, Kansas, Texas, Colorado, New Mexico and Arkansas, primarily due to seismic activity triggered by injecting wastewater deep underground.
Wastewater injection is often associated with the oil and gas extraction method known as hydraulic fracturing, or fracking. However, the USGS says fracking fluid typically makes up less than 10 percent of the injected wastewater. Most of it is saltwater that’s brought up as a byproduct during the oil and gas production process. To avoid polluting freshwater sources, the undrinkable water is typically pumped deep underground over the course of years or decades.
Previous studies have shown a link between wastewater injection and the increased incidence of quakes in Oklahoma. Such quakes aren’t catastrophic, but they do cause damage to buildings – and that’s why they were included in the newly released assessment.
“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 news release. “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.”
The map, and a 52-page report that accompanies it, focuses on the risk of human-induced earthquake damage for the central and eastern United States, going only as far west as the Rocky Mountains and northeastern Arizona. For the Far West, the USGS considered only the natural earthquake risk. That part of the map shows a hot spot centered around Seattle where the risk of a damaging quake is set at up to 5 percent for this year.
University of Washington seismologist John Vidale, director of the Pacific Northwest Seismic Network, told GeekWire that human-induced shaking wouldn’t be that big a factor for Seattle. “We do have a bit of geothermal activity for heating, but as far as we can tell, there’s no heightened risk,” he said.
The best example of the type of risk covered by the USGS’ damage assessment would be the 2001 Nisqually earthquake, which did an estimated $2 billion in damage and injured about 400 people. Over the past year, there’s been a lot of talk about a “Really Big One” that could devastate western Washington, but that type of rare, catastrophic earthquake isn’t well-represented in a year-by-year risk assessment, Vidale said.
About 7 million people live in areas where the USGS saw the potential for damaging quakes caused by wastewater injection and other human activities. The USGS noted that when the human factor is included, some parts of Oklahoma face a risk of earthquake damage that’s similar to that seen in high-hazard areas of California.
The hazard map also shows a heightened risk of quake damage around New Madrid, Mo., which has long been seen as a seismic hot spot. That region has experienced a higher rate of natural quakes in the past two years, the USGS said.
The USGS said it was adding the one-year maps to its 50-year seismic hazard assessments because the risk of human-induced quakes can change relatively quickly due to shifts in industrial practices. For example, induced quakes have become less frequent in some areas of Alabama and Ohio over the past couple of years. Meanwhile, there’s been an uptick in seismic activity in other parts of Alabama and in areas of Mississippi. Scientists are still investigating whether that uptick is due to natural or human-induced causes, the USGS said.
