Risk remains high for damage from human-induced earthquakes

The risk of damage from human-induced earthquakes has declined in some parts of the central US, but it’s still way up since wastewater injection began around 2008, according to the US Geological Survey. On 1 March the agency released a map of potential ground-shaking hazards for that part of the country in 2017. For the second straight year, USGS has issued a short-term risk assessment that includes human-induced quakes.

The hotspot in the new map, like last year’s, is a zone that includes north-central Oklahoma and southern Kansas. In that area the risk of damage, which is defined as the cracking of plaster and masonry, reaches 12% in places. Some 3.5 million people live in the area where there is significant (greater than 1%) risk for damage from human-induced earthquakes. The other hotspot is about 800 km to the east in the New Madrid fault zone, but seismic activity there is natural.

The risk of damage from human-induced earthquakes declined a bit for 2017. The forecasting models use data from the past two years, and the region saw fewer earthquakes in 2016 than in 2015. The at-risk areas also shifted. The hazard chance in the Dallas metro area, for example, was downgraded, and in Oklahoma the risk has shifted slightly eastward.

The changes from 2016 are likely due to less injection of wastewater from oil and gas extraction, says USGS scientist Charles Mueller. He cites mitigation efforts by Kansas and Oklahoma, along with falling petroleum prices, as potential contributors.

Still, on 3 September 2016, a magnitude 5.8 earthquake near Pawnee, Oklahoma, was the strongest earthquake ever recorded in the state. And last year Oklahoma witnessed a record three earthquakes greater than magnitude 5.0; all occurred where the risk of damage was forecast to be at least 5%.

The USGS’s traditional hazard assessment is used for setting building codes that protect structures from natural earthquakes. The forecast incorporates hundreds of years of seismic data and looks forward up to 50 years, a time scale corresponding to the lifetimes of buildings. The new short-term forecasts, Mueller says, can help with assessing dams and other critical facilities, gauging financial risk, and preparing communities for earthquakes. “We are not predicting earthquakes per se,” he says. “We forecast trends in the rates of future earthquakes based mostly on the recent past, and we estimate damage from that.”

The risk due to human-induced seismicity is subject to changes in commercial activities and regulatory decisions, Mueller notes. The maps are part of USGS contributions to the multiagency National Earthquake Hazards Reduction Program .