Two more earthquakes shook the Falls City area of Karnes County, one on early Thursday morning and then another early Friday morning.
The U.S. Geological Survey (USGS) reported the Thursday quake registered a 3.9 on the Richter Scale, and the Friday quake was a 3.5. The Friday quake became the 21st temblor in about 30 days to be reported near the town of 500 people, less than an hour drive southeast of San Antonio.
Most of the quakes have been in the 3.0 range and little more than a curiosity to most local residents.
But Falls City Volunteer Fire Department Chief Raymond Dziuk said the 4.7 temblor on Feb. 17 was a bit different.
"That one got your attention, really kind of like how bad was that going to be," he said. "We didn't end up with hardly any damage to our house, you know, little light cracks in the ceiling in our living room."
Dziuk said residents also reported doors rattling or knick-knacks falling off the shelves.
The fire chief compared it to a train passing right by his house. He said he heard the rumble first and then felt it.
No injuries have been reported, and Dziuk said residents do not seem overly concerned. But he said as a first responder there is always worry that a bigger one could come.
Karnes County is home to some oil production caused by hydraulic fracturing, but the USGS reported most induced earthquakes are not directly caused by "fracking."
The agency explained that the recent increase in earthquakes in the central United States is primarily caused by disposal of waste fluids that are a byproduct of oil production.
Wastewater disposal wells typically operate for longer durations and inject much more fluid than is injected during the hydraulic fracturing process, making them more likely to induce earthquakes, according to the USGS website.
But an assistant professor at UTSA's Department of Earth and Planetary Science suspected the series of recent temblors in Karnes County are linked directly to fracking and not the disposal of waste fluids.
Matt Cannon said the Texas Bureau of Economic Geology installed seismic meters across Karnes County in 2017. He said academic research followed the installation. "There's actually been several papers that have come out as a result that do link the increase in seismic activity directly to fracking, so not just wastewater disposal," Cannon added.
He also said those added monitors mean more seismic activity is being recorded than ever before.
Cannon said it's unlikely, however, the quakes will grow stronger in the future.
The temblors, regardless of size or reason, remain a subject of fascination for many residents in the area, including in San Antonio. In 2022, many Alamo City residents felt sustained shaking from a 5.4 quake in West Texas.
