FLOMATON, Ala. (WALA) – Scientists have a mystery on their hands. What is causing the ground to shake in Alabama’s Escambia County?
Three more earthquakes detected by the U.S. Geological Survey brings the number to eight since March 7. And four smaller ones identified by the agency’s state counterpart raises the total to 12 in fewer than two months.
Smaller earthquakes are quite common across the globe. The Incorporated Research Institutions for Seismology estimates 12,000 to 14,000 occur worldwide every year.
But Elizabeth Cochran, a seismologist with the U.S. Geological Survey, said most of those earthquakes take place along the boundaries of tectonic plates far below the earth’s surface.
“Over there in Alabama and Florida, you’re not actually on a plate boundary,” she said. “So, we see fewer earthquakes away from the plate boundaries in general.”
That does not necessarily mean that the tremblors are caused by drilling or other industrial activity, however.
More data is the key to establishing a connection, Cochran said. After last month’s earthquakes in the Flomaton area, she said, federal authorities installed four additional seismology stations to get more accurate readings. That information will take months – and perhaps as long as a year – to analyze.
But Cochran said the preliminary results suggest the quakes have been fairly deep. For instance, a quake registered 2.8 on the Richter scale on Thursday appears to have occurred more than 5.5 miles underground.
She said that at those depths – roughly one to 10 miles – tremblors tend to be natural events.
“That’s less likely that it’s induced, but again, we really have to look in more detail at whether those depths are correct and then if there’s any other information we have about faults to fluids in the area,” she said.
If the quakes have been induced by industrial activity, it could be due to a drilling method known as hydraulic fracturing – or fracking – which involves the injection liquid at high pressure to break apart underground rocks and to force open fissures in order to suck out oil or gas.
But Cochran said the opposite can trigger quakes, as well. She said authorities in Kansas and Oklahoma have seen large increases in seismic activity over the past decade attributable to a process where energy companies re-inject oil and gas waste created by the drilling process.
Cochran said filling water reservoirs even can cause quakes.
A map produced by the Alabama Oil and Gas Board shows plenty of energy wells in Escambia County, including around Flomaton. But Sandy Ebersole, geologic investigations program director with the Geological Survey of Alabama, said a large number of wells does not prove a link to earthquakes.
Determining “causation based on location, alone, is not a very scientific method,” she said.
Ebersole pointed to Greene County, which saw more than a dozen earthquakes during a nine-month period in 2014 and 2015 even though the area has no oil and gas wells.
If state authorities do suspect a company of causing quakes, there is no specific regulation on the books. Instead, officials said, they would work with the company to address the issue.
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