This morning, a small earthquake went relatively unnoticed in rural Karnes County, some 50 miles southeast of San Antonio. Local law enforcement said they didn't feel it — and they certainly didn't receive calls reporting damage.
But while few felt the 3.1 magnitude quake rumbling underfoot, its impossible to dismiss the significance of yet another earthquake in South Texas' Eagle Ford Shale region.
This is the fourth minor earthquake recorded in this region in 2018. The other three quakes — occurring in both Karnes and Wilson counties — took place over a a four-day period alone. Compare that to 2017, which only saw two quakes in Eagle Ford, and 2016 which saw zero.
Texas doesn't sit on a fault line. Based on the state's geologic makeup, there's no natural reason these counties should be shaking — the cracks in the Earth's crust that run under Texas haven't shifted in 300 million years. Scientists have instead attributed these newer earthquakes to human activity, especially the kind that relies on Eagle Ford's fossil-rich sedimentary rocks.
Researchers with U.S. Geological Survey believe recent drilling from the oil and gas industry
has introduced earthquakes to Texas and surrounding oil-rich states. They argue that fracking, the process of drilling into the earth and using a high-pressure water mixture to extract natural gas, disrupts the fault lines enough to start an earthquake.
And the size of these earthquakes is growing. Sure, Karnes County's 3.1 is minor hiccup compared to the quake that rocked Mexico City
this summer, but it's larger than the region's past shakes.
According to a recent study USGS published with help from Southern Methodist University researchers, the number of earthquakes with magnitude greater than 3 (out of 10) in Texas has increased from 2 to 12 per year.
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