New research links fracking to small earthquakes in the central and eastern United States.

April 26 (UPI) – Scientists have discovered more evidence linking fracking to earthquakes, this time in central and eastern United States.

At the meeting of the Seismological Society of America in 2019, which was held this week in Seattle, researchers detailed the connection between hydraulic fracturing wells and some 600 earthquakes in Ohio, Pennsylvania. , West Virginia, Oklahoma and Texas.

Previous studies have detailed the link between oil and gas activities and earthquakes in Oklahoma, Canada, and China. But these studies have focused mainly on the connection between sewage disposal and seismic activity.

Hydraulic fracturing involves injecting high pressure fluids deep into the rock, usually shale, to trigger the release of oil and gas trapped between the rock layers. Often, the wastewater left behind by the activity is treated and then reinjected into the soil. Oil and gas extraction layers are wetter in places such as Oklahoma, resulting in greater amounts of wastewater and a greater need for disposal.

In states such as Ohio, Pennsylvania, and West Virginia, hydraulic fracturing wells are more common than wastewater injections. Wells in the Appalachians have become increasingly common over the last decade.

"The wells are spaced further apart when they are active and there is less sewage disposal," said Michael Brudzinski of the University of Miami, Ohio, in New York. A press release. "So you can see a little more specifically and directly when sewage disposal generates seismicity and when hydraulic fracturing generates seismicity in the Appalachian Basin."

Brudzinski and his colleagues used a method called multi-station model matching to analyze seismic recordings looking for the signature of small, shallow earthquakes. They compared the seismic signature schedule with the regional fracking schedule.

"The [fracking] The seismic signature, when you look at it in a sort of timeline, shows these bursts of seismicity, hundreds, even thousands of events, over a few days or weeks, then everything becomes calm again. You do not tend to see this model with wastewater disposal, "Brudzinski said.

The research team is currently studying the relationship between different fracturing variables – the type of solution injected into the rocks, the depth of the targeted rock layers – and the risk of an earthquake.

"What struck us most is that the depth of the well is more related to the probability of seismicity than we thought," Brudzinski said.