M4.5 earthquake near Falls City felt as far as San Antonio, Texas

The epicenter was located 20 km (12 miles) ENE of Falls City (population 660), 56 km (35 miles) SSE of Seguin (population 27 864), and 132 km (83 miles) S of Austin (population 931 830).

More than 640 people reported feeling the quake.

According to USGS estimates, around 2 000 people experienced moderate shaking, 54 000 light, and more than 8 million weak shaking.

The USGS issued a Green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.

Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction.

The quake was followed by M2.6 at 06:17 UTC, at a depth of 5 km (3.1 miles).

According to the USGS, there is a 6% chance of aftershocks stronger than M4.0 and a 29% chance of M3.0 or stronger aftershocks within the next week. Aftershocks of magnitude 3.0 or higher are strong enough to be felt in the surrounding areas.

In the central United States, including Texas, earthquakes of this magnitude are relatively uncommon but not unprecedented, with many in recent years linked to human activities such as wastewater injection from oil and gas operations.

Wastewater injection, the primary cause of induced seismicity in Texas, increases underground pore pressure when large volumes of fluid are pumped deep into disposal wells. This added pressure can reduce the friction along pre-existing faults, making them more likely to slip and generate earthquakes.

Unlike hydraulic fracturing, which involves short bursts of fluid injection, wastewater disposal is continuous, allowing stress to accumulate over time.

When fluid migrates through underground rock formations, it can reach critically stressed faults that might not have moved naturally for thousands of years. If the pressure change is significant enough, these faults can slip, causing an earthquake.

The depth and location of these induced quakes often correspond to the injection sites, although sometimes they occur miles away due to the complex nature of subsurface fluid movement.

Seismicity in Texas has increased significantly in the past two decades, particularly in regions with extensive oil and gas activity. The Permian Basin in West Texas, the Eagle Ford Shale in South Texas, and parts of the Barnett Shale near the Dallas-Fort Worth area have all seen noticeable upticks in earthquake activity and studies by the USGS and Texas Seismological Network (TexNet) have confirmed that many of these events are likely induced.

While natural tectonic activity does occur in Texas, the rapid rise in seismic events since the expansion of unconventional drilling methods suggests a strong link between oil and gas operations and earthquake occurrence.

Regulatory agencies have responded by monitoring injection wells more closely and, in some cases, shutting down or restricting high-volume disposal sites linked to seismic activity. However, as long as deep-well injection remains a common practice, the potential for induced earthquakes will persist.

References:

¹ M 4.5 – 19 km ENE of Falls City, Texas – USGS – January 30, 2025