Texas reported its fifth earthquake in just 48 hours, sparking concerns about what could have caused the spate of quakes.
The 2.5 magnitude tremor was believed to be an aftershock from a 4-magnitude event that hit around 10:30 p.m. CST Wednesday.
All five earthquakes have stemmed from the town of Hermleigh in northern Texas, which unleashed a 4.9 magnitude on Tuesday.
The mysterious spate of earthquakes have caught the attention of scientists who believe the state's oil and gas business is to blame.
'We can say with confidence that these are related to oil and gas extractions,' Justin Rubinstein, a geophysicist with the US Geological Survey (USGS) in Menlo Park, California told USA Today.
The quake was felt 200 miles away from the epicenter, affecting 1.6 million people as far away as Austin, southern Oklahoma and New Mexico.
A 4.4 magnitude aftershock hit the area less than 10 minutes later and a third 3.1 magnitude struck on Tuesday morning.
Hermleigh experienced another 4.0 magnitude earthquake shortly before 11 p.m. CST on Thursday and about an hour later experience a 2.5 magnitude aftershock.
Scientists are now speculating that the recent string of earthquakes is largely due to hydraulic fracturing - also known as fracking - which injects wastewater into the earth to release natural gas for energy.
Texas is listed as the number one state for fracking, and as of February 2017, it was home to 279,615 oil and gas wells but by 2023, that number had increased to 373,133 active wells.
The area near where the tremors hit has seen a significant increase in seismic activity since 2019, which the US Geological Survey (USGS) believes is linked to the techniques used to extract oil and natural gas from the ground.
Fracking involves miners drilling deep into the earth's surface and releasing high-pressure water that creates a small explosion to release natural gas and oil that can be used to create energy.
The action brings groundwater to the surface and when it is injected back into the ground, it puts pressure on fault lines, resulting in more earthquakes.
'There are some weaknesses in the bedrock up there,' Moira Plantier, a geology professor at Hardin-Simmons University told 12ABC News in response to the recent quakes that have hit the northern Texas region.
'Most of it is starting to be attributed to a lot of human activity, wastewater injection, different things like that, and that's when we're starting to see a lot of those weaknesses begin to form.'
Colorado, Oklahoma, Ohio and Arkansas have also experienced earthquakes in recent years that have been tied to hydraulic fracturing.
The US Environmental Protection Agency (EPA) has recognized the link between earthquakes and fracking since at least 1990.
It recorded just 21 earthquakes above a 3.0 magnitude per year in Oklahoma between 1967 and 2000, but since the start of the fracking boom in 2010, the state has seen an average of more than 300 quakes.
Although much of the US experiences naturally occurring quakes, the USGS reported that 'in some regions, such as the south-central states, a significant majority of recent earthquakes are thought by many seismologists to have been human-induced.'
The Railroad Commission (RRC) — which oversees and regulates Texas' oil and gas industry - can suspend or terminate saltwater disposal permits if they determine it's contributing to an influx of seismic activity.
In January, the commission suspended 23 permits that allow oil and gas companies to inject wastewater into the ground after it found their practices were causing fault lines to rupture, inducing earthquakes.
The RRC has also introduced a plan that will prohibit operators from injecting wastewater for two years if the area experiences an earthquake of 4.5 magnitude or higher.
It is also exploring other water filtration alternatives to use the wastewater for 'beneficial purposes,' Dr Peter Hennings, a research professor at Austin's Bureau of Economic Geology told KXAN News.
'If we understand why faults rupture in some places and not in others, we can better manage where the injection occurs,' he continued.
'Maybe in the area that experienced the earthquakes in the last few hours, maybe the amount of injection has exceeded the amount that should be injected per day in that area.'
DailyMail.com has reached out to the Railroad Commission and the Bureau of Economic Geology for comment.
