Wastewater Injection Caused Oklahoma Earthquakes

Scientific American, 3 July, 2014.

A new study attributes the recent surge of quakes in central Oklahoma to the injection of wastewater at a handful of high-rate wells across the state.

More than 230 earthquakes with a magnitude greater than 3.0 have shaken the state of Oklahoma already this year. Before 2008 the state averaged one such quake a year. The surge in seismic activity has left residents and experts alike wondering about the underlying cause.

A study published today in Science explains how wastewater injection sites—areas where toxic water left over from oil drilling and fracking processes is injected into the ground between impermeable layers of rocks to avoid polluting freshwater—could be driving the sharp increase in the sometimes-disastrous earthquake events. “It really is unprecedented to have this many earthquakes over a broad region like this,” says study co-author Geoffrey Abers of Cornell University. “Most big sequences of earthquakes that we see are either a main shock and a lot of aftershocks or it might be right at the middle of a volcano in a volcanic system or geothermal system. So you might see little swarms but nothing really this distributed and this persistent.”

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