Four wastewater wells used in oil and natural gas drilling may be responsible for triggering 20 percent of all earthquakes in the central and eastern U.S. from 2008 to 2013, according to a study published today in the journal Science.
The wells are used to dispose of high volumes of wastewater released from underground rocks when they are fractured using modern oil-drilling techniques. The four wells are likely responsible for a dramatic rise in earthquakes near Oklahoma City since 2009, according to the research.
Oklahoma has had more earthquakes than California so far this year, making it the most seismically active state in the continental U.S. and raising suspicions that drilling activity is influencing a surge in temblors there. The state had 238 earthquakes with a magnitude 3.0 or greater through June, more than double the number in California, which has historically ranked second in earthquakes behind Alaska.
Scientists studied wastewater-injection volumes, geologic information and data from earthquake sensors to show that fluids pumped into the wells increased underground pressures and spread them. The area of elevated underground pressure grew in a way that overlapped with a “migrating front” of earthquakes centered near Oklahoma City.
The data showed that water pumped into wastewater wells can increase and affect underground pressures as far away as 35 kilometers (22 miles), potentially triggering earthquakes at faults that would have previously been considered too distant.
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