Damage to the Earth’s Crust and Our Water Supply

Most of the writing about fracking and its effects on humans focuses on health (see Part 1). There is another aspect that appears episodically in the news and that is its effects on the earth itself. This comes to the public mind when earthquakes are reported in association with fracking. The response often is that fracking is responsible for only about 1-2% of these. This is disingenuous. The majority is due to the injection of large volumes of wastewater below the ground water table.  It usually is pooled from many wells before injection below ground. The volumes are large enough to disturb the rock formations. These, in turn, shift and resettle causing earthquakes generally of a Magnitude (M) of 4.5 or less. But that wastewater is recovered fracking fluid and, therefore, is part and parcel of the fracking process and to pretrend that it is unrelated is sophistry.

We have learned over the past few years that earthquakes are caused by fracking itself to a larger degree than previously thought. They can be differentiated from natural earthquakes by their locations and association with fracking activity. Usually they occur where earthquakes do not normally appear, they cluster in a relatively small area, and are temporally associated with increased fracking in that same area. They occur almost anywhere fracking is carried out, but among the best studied are those in Oklahoma, northeastern Ohio, and Arkansas.

At a meeting of the Seismological Society of America in 2019, researchers reported that small earthquakes in Ohio, Pennsylvania, West Virginia, Oklahoma, and Texas can be linked to fracking in those regions. They are of M 2.0-3.8 and may be underappreciated relative to those caused by wastewater disposal. Over the past two decades, there has been a dramatic increase in natural gas production in eastern Ohio and parts of the Appalachian basin. This has been accompanied by a rise in natural gas production from fracking wells. Because of the geology of the area, fracking wells are more prevalent than wastewater disposal wells, so the increase was related to the fracking process itself. Many of many of these studies were carried out by Michael Brudzinski and his colleagues of Miami University in Ohio, who have identified more than 600 small earthquakes in these states. Seismologists have identified these earthquakes as being caused by fracking because of their close link in time and space to fracking operations. Moreover, according to Brudzinski, fracking-related seismicity tends to look different from that caused by wastewater disposal, and this aids in making the distinction. (ScienceDaily, 26 April 2019. <www.sciencedaily.com/releases/2019/04/190426110601.htm>.) 

Similarly, Yoon and al., published in 2017, (https://doi.org/10.1002/2017JB014946) studied an earthquake that occurred in Arkansas in 2011, after months of smaller earthquakes that started about a year before. These were thought to be due to the injection of wastewater but, subsequently, were shown to be a result of the fracking process. They reached the conclusion by identifying as many earthquakes as possible, using seismological methods, and showed that fracking, with its high-pressure injections of fluid, produced many small earthquakes that go unnoticed - as was the case in the studies of Brudzinski and colleagues. 

The central and eastern United States has an intraplate region with very low levels of seismicity. However, central Arkansas experienced a strong increase in earthquake activity after fracking began that lasted about a year.  These were thought to be caused by injection of wastewater, but the investigation by Yoon et al. showed that fracking itself produced several moderate strike slip earthquakes of M 4.0 and then several months later a large earthquake of M 4.7. These earthquakes migrated southwest over several months and demonstrated the existence of a fault that was previously unknown. After the large earthquake, injection was halted at the wells near the fault and the seismic activity decreased but remained higher than the background rate for at least the next seven months.

Oklahoma has had the most induced earthquakes in the United States. There has been a surge since 2009, and all are related to the fracking process in some way. It appears at this time that a minority, about 2%, are due to fracking and most are due to wastewater disposal. However, I believe it is sophistry to pretend that wastewater-induced earthquakes are unrelated to the fracking process. Wastewater is a byproduct of fracking. 

Quakes have decreased since 2016 because the Oklahoma Corporation Commission has been shutting down wastewater disposal wells or cutting wastewater disposal amounts. The Oklahoma University Geology and Geophysics Department believes that the decrease in earthquake frequency came from the reduction of wastewater injections. Wastewater disposal wells are created to hold water from many fracking wells. Therefore, much more water goes into them than into a fracking gas or oil well. They also operate longer than hydraulic fracking which makes them more likely to induce earthquakes, according to the United States Geological Survey.

Although the seismic activity in Oklahoma is decreasing, the earthquakes may continue. According to Professor Chan of the Oklahoma Department of Geology and Geophysics, in an area of Colorado earthquakes lasted for 10 years. This was decades following the shutdown of a fluid injection site. In Texas, seismic activity continued for about seven years after wastewater disposal was decreased. So, probably there will be continued seismic activity in Oklahoma due to the fracking process for some years.

The fracking process has brought about inexpensive natural gas and decreased carbon emissions compared to the coal it has displaced. However, it has levied a cost in human and animal health, caused much environmental damage, and created seismic activity where there was little or none before. Has it been worth it? 

 Next, we will look at the cost/benefit relationships of fracking.