And in those areas where wastewater injection might be a seismological threat, he said, there may be other disposal options.
The San Antonio Express-News reports,
First the well is drilled, and then highly pressurized fluid is injected to break up the rock. This increases the rate at which natural gas can be produced from the well.
At that point something must be done with the wastewater used to frack the well. To avoid contaminating nearby groundwater, it often is injected back, deep into the well.
It is this step, scientists believe, that can trigger earthquakes.
Although the world’s strongest earthquakes occur along the major fault lines, there are smaller, pre-existing faults all over.
The injection of water can change the pressure along these faults, causing them to slip and triggering small earthquakes, scientists say. Fracking, then, might cause an earthquake sooner than it would have occurred naturally.
But the process seems unlikely to amplify a tremor.
“My preliminary studies suggest you almost never get induced earthquakes that are bigger than the natural earthquakes in an area,” said Cliff Frohlich, a researcher at the University of Texas at Austin’s Institute for Geophysics.
That was the case even with the Youngstown quake.
As recently as 1998, there was a magnitude 4.5 earthquake near the city, according to the U.S. Geological Survey.
Although scientists say they have a basic understanding of fracking and earthquakes, more research is needed to put further limits on the risk posed by the process.
“I think it’s a manageable problem,” Frohlich said. “To me it seems that, especially if more research were done, it’s possible to establish some areas of the country where you could do almost any amount of injection.”
And in those areas where wastewater injection might be a seismological threat, he said, there may be other disposal options.