Oil and gas operations could trigger large earthquakes 7.0
Oil and gas operations could trigger large earthquakes 7.0
The U.S. Geological Survey (USGS) has taken its first stab at quantifying the hazard from earthquakes associated with oil and gas development. The assessment, released in a preliminary report today, identifies 17 areas in eight states with elevated seismic hazard. And geologists now say that such induced earthquakes could potentially be large, up to magnitude 7, which is big enough to cause buildings to collapse and widespread damage.
The new bull’s-eyes on the map, regions such as central Oklahoma, have short-term hazards that are comparable to the those in traditional earthquake states, like California, says Mark Petersen, chief of the USGS National Seismic Hazard Mapping Project in Golden, Colorado. “These earthquakes are occurring at a higher rate than ever before and pose a much greater threat to people living nearby,” he says. “This report represents our first step in identifying and quantifying the ground shaking from induced earthquakes.”
Geoscientists have known for decades that the injection of fluid can increase pressures within the pores of deep rock formations, pushing faults that are already critically stressed by forces in Earth’s crust past the snapping point. But the phenomenon has been brought to the fore by an extraordinary rise in small earthquakes across parts of the central United States. That surge has coincided in time and place with the boom in unconventional oil and gas extraction such as hydraulic fracturing, or "fracking," in which high-pressure fluid is injected into the ground to break up the underlying rock and release trapped gas or oil. In most cases, the earthquakes are not due to fracking itself, which is usually completed in hours or days. Rather, the culprit is typically wastewater disposal, where high volumes of water extracted in oil and gas operations is reinjected into deep basement rocks, where the bigger and more dangerous faults lie.
So far, the largest induced earthquake in the United States has been the 2011 magnitude-5.6 earthquake in Prague, Oklahoma, which damaged dozens of buildings. But geoscientists now say there is no reason why oil and gas operations couldn’t end up triggering something much larger. “There are certainly faults large enough to produce a magnitude 7,” says Justin Rubinstein, a geophysicist at USGS in Menlo Park, California, and a co-author of the new report. “We can’t rule this out.”
http://news.sciencemag.org/earth/2015/04/oil-and-gas-operations-could-trigger-large-earthquakes
We need more fracking around yellowstone..........