Over the last week the state of Arkansas has experienced some fifty-plus earthquakes. In fact, over the past six months the state has recorded over 700 in the past six months. Some would say that the cause would appear to be a previously undiscovered fault line or an activity spike with the network of smaller faults that run under the state.
As it turns out, the earthquakes may very well be man made. Two areas which have experienced some of the most powerful (“powerful” in relative terms) quakes are Guy and Greenbrier, which are located near areas of natural gas extraction. According to University of Arkansas professor Hanan Mahdi, this natural gas extraction could be at least partially to blame for the quakes.
People say ‘well, there were earthquakes here before the natural gas companies started, why should it be different now?’ Really, it could be both [gas extraction and fault activity]. We need to study this more and get a better picture of the geology here.
So, how could natural gas extraction lead to earthquakes? One byproduct of extracting natural gas is salt water. This salt water is often toxic, so the easiest thing to do is to pump it back into the ground. The salt water could then lubricate the rock as it’s pumped, leading to easier sliding of the existing faults which would result in more earthquakes.
While the earthquakes in Arkansas have been a somewhat common occurrence as of late, Dr. Mahdi doesn’t expect them to approach the 5.5-magnitude earthquake that hit in Missouri thirty years ago.
If you were in the New Madrid Seismic Zone I might expect it, as it has happened in the past and might happen in the future. But it hasn’t happened here [in Arkansas].
So if you live in Arkansas and feel a bit of a tremor under your feet, try not to panic. It’s just a bit of a shake.