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If you live in the East Texas town of Timpson, or nearby, chances are you’ve had a shaky week. It all started last Friday, very early in the morning, when an earthquake measuring 4.1 on the Richter scale struck just north of town, causing minor damage. Then on Tuesday, again, very early in the morning, a smaller 2.8 quake struck. Then yesterday afternoon another quake occurred, just south of town, with a strength of 2.7. That’s three earthquakes within a week.
So what’s going on? We put that question to Dr. Cliff Frohlich, a seismologist that studies manmade earthquakes at the University of Texas at Austin. Yes, manmade.
Frohlich has looked into a string of quakes in the Dallas-Fort Worth area that began in 2008. Frohlich has linked many of those quakes to deep injection wells used to dispose of wastewater from oil and gas drilling, which has taken off in recent years with the advent of hydraulic fracturing and horizontal drilling. (You can read more about how disposal wells work here.)
“Those [DFW] earthquakes started only six weeks after [disposal] injection,” Frohlich says. “At the same depth, and within a kilometer of the well.” Frohlich has conducted two peer-reviewed studies of quakes in that area, linking them to injection wells. “Injection-triggered earthquakes are more common than is generally recognized,” he writes in his latest study.
But is that what’s happening in East Texas? The largest earthquake to ever strike the area hit Timpson (in Shelby County) directly last May, with a magnitude of 4.8. “The highest intensities … occurred south of Timpson … where chimneys, fireplaces, and brick veneer siding suffered significant damage,” Frohlich and two others write in a review of that quake recently presented to the American Geophysical Union. (Earthquakes below an intensity of 4.0 generally aren’t known to cause significant damage.)
There have been earthquakes in the surrounding area in the past, but nothing this big. And Timpson has never experienced earthquakes, according to U.S. Geological Survey measurements dating back to 1973. There are 27 active disposal wells in Shelby County, according to the Railroad Commission of Texas’ database, with two of them in Timpson.
So are the Timpson earthquakes connected to disposal wells? It’s certainly possible, Frohlich says. He’s leading a team studying a potential link, and their research could be ready by the end of the year. But one thing slowing him down? The area keeps shaking, meaning they have to keep adding more data. “If they quit having earthquakes it’d be faster,” he says.