Earthquakes triggered by man-made practices have risen sharply in the United States since 2009, especially in the central part of the country, prompting the U.S. Geological Survey to outline a preliminary set of models to forecast the frequency and severity of future temblors.
Oklahoma has been the state hardest hit by the increased rates of magnitude-3 or higher quakes blamed on industrial operations that dispose of wastewater by injecting it into deep wells, followed by Texas, Kansas, Colorado, New Mexico and Ohio, the USGS said in a newly released study.
“This new report describes for the first time how injection-induced earthquakes can be incorporated into U.S. seismic hazard maps,” Mark Petersen, chief of the USGS National Seismic Hazard Modeling Project, was quoted as saying in a press release Thursday.
“These earthquakes are occurring at a higher rate than ever before and pose a much greater risk to people living nearby. The USGS is developing methods that overcome the challenges in assessing seismic hazards in these regions in order to support decisions that help keep communities safe from ground shaking,” the release said.
All of the areas where increased seismicity has been detected “are located near deep fluid injection wells or other industrial activities capable of inducing earthquakes,” the USGS said.
The study also referred to hydraulic fracturing, or fracking, a controversial hydrocarbon extraction technique that involves pumping a pressurized fluid – usually composed of water, sand and chemicals – into a shale formation to create a fracture in the rock layer and release trapped petroleum or natural gas.
Shale accounted for around 40 percent of U.S. dry natural gas production in 2012, the U.S. Energy Information Administration said in a report last year.
The USGS, however, downplayed the role of fracking in the increased seismic activity.
“Many questions have been raised about whether (fracking) is responsible for the recent increase of earthquakes. USGS’s studies suggest that the actual hydraulic fracturing process is only occasionally the direct cause of felt earthquakes.” EFE