NEW ORLEANS – A series of unusual earthquakes in northwest Louisiana, called an earthquake swarm, has prompted Tulane University geoscientist Cynthia Ebinger to deploy seismic monitoring equipment near Coushatta where at least 14 earthquakes with magnitudes greater than 2.5 have been recorded since December. According to the U.S. Geological Survey, the recent swarm of seismic activity included the largest inland earthquake ever documented in the state.
Ebinger, the Marshall-Heape Chair in Geology in Tulane University’s School of Science and Engineering, installed the equipment to help researchers better understand a sequence of tremors in Red River and DeSoto parishes. The most significant event occurred March 5 and measured magnitude 4.9.
The earthquake cluster has drawn attention in part because it lies within the Haynesville–Bossier Shale formation, one of the largest natural gas production regions in the United States and a major driver of Louisiana’s energy economy.
“Scientists at the U.S. Geological Survey have used new data from instruments we recently installed to relocate the earthquakes,” Ebinger said. “They are occurring in crystalline rocks much deeper than any of the industrial activity and along an ancient fault line.”
Researchers say the newly deployed monitoring array will help scientists determine the location, depth and movement of the faults responsible for the earthquakes as the sequence continues.
Five additional earthquakes were recorded in the most recent cluster, and scientists say the activity could continue as researchers collect more data.
Understanding Underground Activity
The investigation also highlights a growing scientific focus on how underground energy activity can interact with natural fault systems.
North Louisiana sits atop the Haynesville Shale, one of the nation’s largest natural gas production regions and a key supplier for the Gulf Coast’s expanding liquefied natural gas export industry.
Scientists have documented cases in other states where wastewater produced during oil and gas extraction and injected back underground can trigger earthquakes under certain geological conditions.
“Throughout the U.S. and elsewhere, we’ve learned that injecting wastewater produced during oil and gas extraction back into deep wells can cause earthquakes,” Ebinger said. “Over time, the added weight of the injected water can put pressure on ancient faults and cause them to reactivate.”
Researchers emphasize that determining whether human activity plays a role in the Louisiana earthquakes will require additional analysis.
“The question of natural earthquakes versus human-induced earthquakes does not have a simple yes-or-no answer,” Ebinger said. “But the increase in the number and magnitude of earthquakes over the past 15 years since we’ve had local monitoring suggests something is changing.”
Mapping Louisiana’s Subsurface
Ebinger leads Tulane’s Geophysics and Active Tectonics Research (GATR) Laboratory, which studies the forces that deform Earth’s crust and shape tectonic plate boundaries. Her team’s work builds on earlier monitoring efforts across Louisiana.
Between 2019 and 2022, geoscientists installed seismometers across parts of the state to track subtle ground movements and establish a baseline of earthquake activity.
“Those instruments measure vertical and horizontal ground motions so small they can’t be detected at the surface,” Ebinger said. “Our goal was to establish a baseline for earthquake activity to inform state planners and to better understand Louisiana’s subsurface structure.”
That monitoring revealed clusters of small earthquakes and suggested activity in some areas may be increasing. A new Tulane array of instruments installed in October captured the recent earthquake sequence, providing scientists with detailed information about the events. The instruments measure earthquake locations, depths, directions of fault movement and ground acceleration — the shaking people may feel at the surface.
“Owing to the quick USGS response, Tulane data are now monitored remotely and automatically transmitted to a national automated system that collates and uses information from Texas, Arkansas, Mississippi and throughout the United States,” Ebinger said. “That allows scientists to quickly analyze earthquake locations and ground shaking and then combine those results with older data to visualize the subsurface faults.”
Assessing Earthquake Swarm Risk
Researchers are now using aftershocks and other measurements to map the fault systems responsible for the earthquakes and improve hazard assessments.
“We are using aftershocks to map out the fault plane or multiple fault planes,” Ebinger said. “We’re also measuring ground acceleration so engineers can use that information for hazard zoning and improved ground-shaking maps.”
For residents and businesses, the key concern is not simply whether earthquakes occur but how strong the ground motion becomes.
“Earthquakes happen all the time,” Ebinger said. “The important factors are the magnitude of the earthquake and the ground acceleration it produces. Fortunately, we now have instruments in place to collect that critical information.”
As Louisiana’s energy sector continues expanding, from natural gas production in the Haynesville Shale to emerging carbon capture and storage projects that involve injecting carbon dioxide deep underground, researchers say a better understanding of the state’s subsurface geology will become increasingly important for both economic development and long-term land stability.
