Powerful earthquakes thousands of kilometers away can trigger swarms of minor quakes near wastewater-injection wells like those used in oil and gas recovery, sometimes followed months later by quakes big enough to destroy buildings.

 

A discovery, published in the journal Science by one of the world's leading seismology labs, threatens to make hydraulic fracturing, or "fracking," which involves injecting fluid, particularly wastewater, deep underground, even more controversial.

 

Geologists have known for 50 years that injecting fluid underground, commonly done to extract natural gas and oil, can increase pressure on seismic faults and make them more likely to slip. The result is an "induced" quake.

Quakes with a magnitude of 2 or lower, which can hardly be felt, are routinely produced in fracking. But evidence was found that injection wells can set the stage for more dangerous quakes. Because pressure from wastewater wells stresses nearby faults, if seismic waves speeding across Earth's surface hit the fault it can rupture and, months later, produce an earthquake stronger than magnitude 5.

 

However, current federal and state regulations for wastewater disposal wells focus on protecting drinking water sources from contamination, rather than earthquake hazards.