Texas does experience earthquakes, although it is not situated near a major tectonic plate boundary. The state’s seismic activity has historically been low, but it includes both naturally occurring events and an increasing number of tremors linked to human industrial activity. Texas geology features ancient, deep-seated fault systems that can become active under certain conditions. Understanding the nature of these tremors requires looking at where they occur and the specific causes that trigger movement along these faults.
Historical and Geographical Seismic Activity
Naturally occurring earthquakes in Texas are generally infrequent and of lower magnitude compared to quakes in plate boundary regions. The most significant historical natural event was the 1931 Valentine earthquake in West Texas, estimated to have reached a magnitude of 5.6 to 6.4. Another large natural quake, a magnitude 5.7 tremor, occurred near Alpine in the same region in 1995. These larger quakes are often associated with the Rio Grande rift zone, a region of crustal extension that affects the Trans-Pecos area of West Texas.
Other areas with natural seismic risk include the Panhandle, where ancient faults underlying the Amarillo Uplift can be reactivated. Earthquakes in these zones are caused by the slow, long-term movement of the Earth’s crust along existing zones of weakness in the basement rock. Historically, natural quakes in the Texas Panhandle have been recorded up to a magnitude of 5.4. Minor tremors have also occurred along the Gulf Coastal Plain, potentially linked to the growth of salt domes and regional sediment loading.
Understanding Induced Seismicity
Induced seismicity refers to earthquakes caused or triggered by human industrial activities, which have become the dominant source of tremors in modern Texas. The primary cause is the disposal of massive volumes of produced water, a toxic brine that is a byproduct of oil and gas extraction. This wastewater is pumped deep underground into saltwater disposal wells, often reaching depths near or into the crystalline basement rock where ancient faults lie. This process is distinct from hydraulic fracturing, or fracking, as the disposal of wastewater is the main mechanism driving induced quakes.
Injecting this fluid increases the pore pressure within the rock formation, which acts to decrease the friction on pre-existing faults. If the pressure increase is sufficient, it can cause a fault that was already under tectonic stress to slip. Since 2008, the rate of earthquakes with a magnitude of 3.0 or greater in Texas has increased significantly, largely attributable to this wastewater disposal.
The Permian Basin, particularly the area around Midland and Odessa, and parts of North Texas, have been the most affected by this induced activity. These areas, which include the Fort Worth Basin and the Delaware Basin, have seen a sharp rise in seismic events coinciding with the high-volume injection of produced water annually. The induced quakes tend to occur within a few kilometers of the deep disposal wells. Scientific analysis has established a clear temporal and spatial correlation between high-rate injection and the onset of seismic swarms in these regions.
State Monitoring and Regulatory Measures
The state of Texas tracks and investigates seismic events through a coordinated effort involving scientific and regulatory bodies. The Texas Seismological Network (TexNet), managed by the Bureau of Economic Geology, monitors earthquake activity using a network of seismometers across the state. TexNet collects precise data on the location, depth, and magnitude of tremors, helping to distinguish between natural and induced events.
The Railroad Commission of Texas (RRC), which regulates the state’s oil and gas industry, uses TexNet data to inform its regulatory decisions regarding disposal wells. The RRC has established specific protocols, including the creation of Seismic Response Areas (SRAs) in high-risk zones, such as the Gardendale and Stanton areas in the Permian Basin. Within an SRA, the RRC can issue mandates to operators to reduce or cease injection volumes to mitigate seismic risk.
When an earthquake of magnitude 3.5 or greater occurs, the RRC takes immediate action to investigate and may require operators to adjust their disposal well permits. These regulatory actions are aimed at lowering the pressure buildup on faults contributing to induced seismicity. The state’s monitoring and regulatory framework is a direct response to the increase in induced earthquakes, using scientific data to manage industrial activity and reduce the seismic hazard.