In recent years the Fort Worth Basin located in North Central Texas has become a major shale gas production region. In order to extract oil and gas trapped in the rock, wastewater is injected deep into the ground and works its way into dormant faults and eventually forces the rock to crack and allow fossil fuels to seep out. While we’ve known for some time that wastewater injection causes earthquakes, new evidence shows that they continue to affect communities even after oil and gas exploration activities stop.
The Science: Researchers have observed that through water injection, previously dormant faults within the basin were reactivated and they continue to release leftover energy. Overall seismic activity in the Fort Worth Basin has been strongly correlated with wastewater injection activities and most earthquakes occur within 15 km of disposal wells. However, as a consequence of past water injection techniques, seismic activity is occurring at greater distances from injection wells over longer periods of time, suggesting that these techniques are causing leftover energy on all sorts of little faults being released and continue causing earthquakes.
Growing With Time: Between the years 1973–2008, there was an average of 25 earthquakes of magnitude three and larger in the central and eastern United States.
- Since 2009, the average number of magnitude 3 or greater earthquakes jumped to 362 per year.
- In 2015, there were 1010 magnitude 3 or greater earthquakes
Not Just a Texas Problem: In 2018, the state of Oklahoma experienced a series of magnitude 4 or greater earthquakes, which forced operators of the School Land 64 well to reduced well injection from 17,00 to 5,000 barrels a day. The situation has gotten so bad in Oklahoma that the earthquake threat level in some parts of the state may now be approaching the level for some parts of California
Why This Matters: In an effort to utilize America’s abundance of natural gas, fracking and wastewater injections increased tremendously in the past decade yet the industry and regulators didn’t fully consider the long-term effects of these practices in the communities where they occur. In order for proper regulations to be put in place, scientists need to understand these earthquakes better which will require industry releasing their injection data–something they haven’t done yet. If the people of North Texas are going to keep experiencing residual earthquakes, then they deserve to know the full truth of what they should be expecting.