A new study published this month purports to link seismic activity in Kansas to wastewater disposal associated with hydraulic fracturing. Justin Rubinstein, the lead researcher, suggested that further research was needed to examine the effects of wastewater injections, stating that this study was “the tip of the iceberg as far as what we’re going to learn.”

The study examined ongoing seismicity in two counties in southern Kansas from 2013-2016, observing correlations between increases in seismic activity subsequent to increases in wastewater disposal via deep-injection wells. Additionally, seismic activity appeared to decreased at the same time as economic and regulatory forces reduced wastewater injection. Analyzing over 6,845 earthquakes, the study also identified six earthquakes of magnitude 4 or greater in Kansas since 2012, the first such earthquakes in the state.

Importantly, the study notes that hydraulic fracturing and oil production do not correlate in space or time with seismicity. The study’s conclusions instead attribute increases in seismic activity solely to wastewater injection. Moreover, the researchers indicated that not all wastewater injection disposal sites are associated with earthquakes because some areas may be more susceptible to the purported geological effects of wastewater injection than others.

Similar studies on wastewater disposal have failed to explain why other areas of the country have experienced few earthquakes despite having disposal wells with high injection rates. Rubinstein’s study reflects this important discrepancy, observing an absence of seismicity near the largest injection operations in the study area. The researchers attribute this observation to differences in local geological conditions. However, this inconsistency potentially undermines the study’s conclusion that higher levels of wastewater injection can lead to increased earthquakes.

Many state lawmakers have increased regulatory restrictions as a result of similar observations regarding wastewater injection. The Kansas Corporation Commission, for example, promulgated regulations in 2015 to limit wastewater injection. These regulations reduced wastewater injection in the area monitored in Rubinstein’s study by nearly 50%. Still, Rubinstein stated that it is difficult to tell how much economic shifts or new regulations concerning wastewater disposal contributed to decreases in seismic activity.

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