After at least a dozen earthquakes hit North Texas in 36 hours, geophysicists said they're looking into whether fracking might have been a factor. The largest quake hit Irving, Texas, with a magnitude of 3.6 on Tuesday evening. By then, local nerves were already frazzled from the initial 2.7-magnitude earthquake that hit Tuesday morning and the 3.5-magnitude earthquake that hit earlier in the afternoon. "It could just be a natural event that just happened to occur," Robert Williams, a geophysicist with the USGS, told NBC News. "We're going to be exploring all possibilities, including any contributions that the oil and gas industry might have in terms of injection of fluids or extraction of fluids in the subsurface."
Earthquakes have historically been rare in the area. That means scientists know very little about the cause of temblors in the area as compared to in seismic hot spots like California. "Generally speaking, we have not been studying earthquakes in our backyard until recently," Heather DeShon, an associate professor of geophysics at Southern Methodist University, told NBC News. She said that studies had linked fracking with increased earthquake activity in North Texas and Oklahoma, but urged against jumping to conclusions, saying "We cannot say yet what's causing the Irving earthquakes."