EARTHQUAKES. Between 1847 and 1994 there were more than 110 recorded earthquakes of magnitude three or greater in Texas.
No Texas earthquake has exceeded a magnitude of 6.0, and most have been fairly small and caused little or no damage.
Damage has occurred in at least twenty-five of the recorded earthquakes, however, and one death has been attributed to a Texas quake.
Almost all of the earthquakes in Texas have been caused by one of two sources.
The major source is relief of tectonic stress along fault lines. These are most common in the Rio Grande rift belt, the Panhandle, the Ouachita Belt, and the Coastal Plain.
Small earthquakes have also been attributed to well injections associated with oil and gas field operations and occur in areas near large oil and gas fields.
The first known earthquake in Texas occurred in Seguin and New Braunfels on February 13, 1847.
The largest earthquake in Texas occurred on August 16, 1931, near Valentine in Jeff Davis County; it measured about 6.0 on the Richter Scale.
Many of the other West Texas earthquakes have occurred in El Paso, including the only Texas quake associated with a death; on March 7, 1923, in Ciudad Juárez, Chihuahua, a few kilometers from the quake’s epicenter, an adobe house collapsed and suffocated the man inside.
Some of the larger earthquakes in the Panhandle include the 1917, 1925, and 1936 Panhandle and Borger quakes and the 1948 Dalhart quake. No earthquake in the Panhandle has exceeded a magnitude of 5.0.
Earthquakes in East and Central Texas have been fairly small. Some notable ones have occurred at Manor (1873), Paige (1887), Creedmore (1902), Mexia-Wortham (1932), and Trout Switch (1934). Other significant earthquakes have occurred in Wellborn (1857), Hempstead (1910), and Anderson (1914) in the Southeast and in Rusk (1891), Center (1981), and Jacksonville (1981) in the Northeast.
In April 1993 an earthquake of magnitude 4.2 that took place in Atascosa County damaged homes and a gas pipeline.
On April 14, 1995, the second largest earthquake in Texas struck West Texas near Alpine. The quake measured 5.7 and caused alarm and minor damage in Alpine, Pecos, Fort Davis, and Marathon. The event generated widespread reports in the national media.
Three years later, another tremor of magnitude 3.6 shook Alpine. The South Texas town of Alice reported a small earthquake of magnitude 3.8 on March 24, 1997, and in August 2000 Amarillo experienced a series of six earthquakes of magnitudes ranging from 2.7 to 3.3. The tremors caused hairline cracks in underground pipes and gas lines and in the walls of some buildings.
An unnatural number of earthquakes hit Texas in the past decade, and the region’s seismic activity is increasing. In 2008, two earthquakes stronger than magnitude 3 struck the state. Eight years later, 12 did.
There has been a recent increase in natural gas extraction — including fracking, or hydraulic fracturing, but other techniques as well — which produces a lot of wastewater. To get rid of it, the water is injected deep into the ground. When wastewater works its way into dormant faults, the thinking goes, the water’s pressure nudges the ancient cracks. Pent-up tectonic stress releases and the ground shakes.
Given the lack of faults in Texas’s most recent 300 million years of history, there is no known geologic process that could explain its sudden quake outbreak. “There is no other explanation” except that these earthquakes are caused by human activity, Magnani said.
The study is in line with what other earthquake experts had surmised using different analyses. “We don’t expect a lot of pushback” from the scientific community, Blanpied said.
“This is a landmark contribution in the question of whether the Fort Worth basin earthquakes are man-made,” said Cliff Frohlich, a geophysicist at the University of Texas at Austin who was not involved with the study. Frohlich said this research eliminates the possibility, sometimes raised by the oil and gas industry, that the Texas quakes are part of a natural cycle of faults that awaken every few thousand or million years.
The seismic reflection data provide a powerful argument “that these earthquakes are something new and different,” he said — activity stemming from the injection of wastewater deep into basement rock. (“Most of the time it’s the large volume injection,” he said, “not the little frack jobs.”)
In March 2016, the USGS published a map of the likely areas where human-made earthquakes will strike in the United States. About 7 million people are at risk of these events, with Texas and nearby Oklahoma among the most susceptible states.