While Texas is not typically associated with frequent seismic events like California, earthquakes do occur within the state. The frequency of these events has noticeably increased in recent decades.
Seismic Activity in Texas
Texas has a history of seismic activity, with the earliest recorded earthquake occurring near Seguin and New Braunfels in 1847. Over 100 felt earthquakes were recorded in the 20th century across 40 Texas counties. The strongest was the 1931 Valentine earthquake in West Texas, estimated between magnitude 5.6 and 6.4, felt across much of Texas and neighboring states. A magnitude 5.7 tremor occurred near Alpine in 1995.
Since the early 2000s, Texas has experienced a notable increase in earthquake frequency. Between 2008 and 2016, the average number of earthquakes with magnitudes greater than 3 rose from about two to twelve per year. In 2023, Texas recorded 2,493 earthquakes of magnitude 2.0 or higher, more than double the amount in 2020. Most Texas earthquakes are minor, many below magnitude 3.0, but some are strong enough to be felt.
Geographic hotspots include West Texas, particularly the Permian Basin and Pecos area, which has seen significant increases in activity since 2009. The Texas Panhandle, North Texas (including Dallas-Fort Worth), and South Central Texas have also experienced increased seismicity.
Natural Geological Influences
Earthquakes in Texas can arise from natural geological processes, even though the state is not on an active plate boundary. Texas is within the stable North American Craton. Intraplate earthquakes, occurring far from plate edges, can still happen due to stress buildup and release within the continental crust.
The state contains numerous ancient fault lines, remnants of past geological activity. These include the Balcones Fault Zone, running from Del Rio to Dallas, and faults from the Ouachita Orogeny, a mountain-building event hundreds of millions of years ago. The East Texas Basin also features fault systems formed by underlying salt deposits.
Many ancient faults, like the Balcones Fault, have been largely inactive for millions of years but represent zones of weakness. Stress can accumulate along these structures from regional forces. When this stress exceeds rock strength, these faults can reactivate, leading to an earthquake. Natural seismicity in Texas is linked to the reactivation of these older fault systems under current regional stress fields.
Human Activities and Earthquakes
Beyond natural geological influences, a significant portion of Texas’s increased seismic activity links to human industrial operations, particularly oil and gas production. Scientific consensus, supported by studies, points to deep underground wastewater injection as a primary cause of induced earthquakes. This wastewater is a byproduct of oil and gas extraction.
Injecting this wastewater into deep geological formations increases fluid pressure, known as pore pressure. This elevated pore pressure counteracts forces holding fault lines together, reducing normal stress and making them susceptible to slipping. Dormant faults can reactivate under these conditions, leading to earthquakes.
While hydraulic fracturing (“fracking”) involves high-pressure fluid injection, it is rarely the direct cause of felt earthquakes. The main concern is the disposal of vast quantities of wastewater produced during and after these operations. Disposal wells operate longer and inject larger fluid volumes than fracking, leading to more widespread pressure changes underground.
Regions with intensive oil and gas development, such as North Texas (Dallas-Fort Worth and Azle) and the Permian Basin (Pecos, Midland, Odessa), have experienced increased seismic activity correlated with wastewater disposal. A 2016 study concluded that 59 percent of Texas earthquakes since 1975 were likely caused by oil and gas activities. This evidence highlights the impact of industrial practices on the state’s seismic landscape.
Monitoring and Mitigating Seismic Events
In response to increasing seismic activity, Texas has implemented significant monitoring and mitigation efforts. A primary initiative is the TexNet Seismic Observatory, operated by the Bureau of Economic Geology at The University of Texas at Austin. Established in 2017, TexNet deploys a statewide network of seismometers to detect, locate, and report on earthquakes, providing data to distinguish between natural and human-induced events. The TexNet Earthquake Catalog offers public access to recorded seismic activity.
Complementing TexNet, the Center for Integrated Seismicity Research (CISR) investigates induced seismicity causes. This research aims to understand the interplay between geological structures and fluid injection, informing regulatory decisions and industry practices. CISR collaborates with TexNet, industry, and state regulatory agencies to understand Texas seismicity.
The Railroad Commission of Texas (RRC), the state’s oil and gas regulatory body, plays a central role in mitigating induced seismicity. The RRC established Seismic Response Areas (SRAs) in regions with elevated earthquake activity, such as the Permian Basin (Northern Culberson-Reeves, Gardendale, Stanton). Within SRAs, the RRC can modify, suspend, or terminate saltwater disposal well permits if injection contributes to seismic events, as outlined in 16 Texas Administrative Code ยง3.46.
Regulatory responses include requiring operators to report injection volumes and pressures more frequently, and sometimes mandating reductions in disposal volumes or suspending permits. These actions are based on ongoing data analysis and collaboration among scientists, regulators, and industry. While Texas earthquakes are generally not as powerful as those in major seismic zones, these efforts are important for managing risks and promoting public safety.