Earthquakes Induced by Hydraulic Fracturing and Wastewater Disposal in the Appalachian Basin

Dr. Mike Brudzinski's research group at Miami University has published several studies showing a clear link between oil and gas related operations and earthquakes in the Appalachian Basin. We have identified over a dozen cases since 2010 where hydraulic fracturing (“fracking”) has produced earthquakes above a magnitude of 2.0. This is based on nearly all of the earthquakes occurring when the fracking was within a mile of a fault in deeper, older rock. Nearly 10,000 other wells that were fractured since 2010 did not induce earthquakes. In the cases that did, only certain stages of the operations that were closest to the fault caused earthquakes, while hundreds of other stages did not. So our studies suggest that fracking needs to be very close to an existing fault for it to have a chance to induce earthquakes. This helps explain why earthquakes induced by fracking are rare. Considering how rare this is, we are not advocating to ban fracking. Instead, our studies suggests that we can use better monitoring techniques to help provide early warning if an operation is causing a nearby fault to slip, so those operations might be adjusted to limit the induced earthquakes.

Figure 1. Map summarizing our analysis of earthquakes in the Appalachian Basin from Brudzinski and Kozlowska (2019). The small symbols are all hydraulic fracture wells (pink) and wastewater disposal wells (cyan). The large symbols are earthquakes correlated with fracking (red) and wastewater injection (blue). The open circles are earthquakes that appear to be natural. The Y labels the Youngstown case where a magnitude 4.0 earthquake occurred due to wastewater disposal.

At this point, we would not recommend that companies be required to find the existing faults beforehand, because many of the faults that are being activated could be very difficult to find. This is because the advanced (and expensive) scans the industry already does to identify the target rock layer for drilling reveals the layering of rocks below the ground. These scans have a hard time seeing the small east-west side-to-side motion faults that are being activated in places like the Appalachian Basin and would not cause much offset in the rock layers. The lack of a definitive technology to find this type of fault before drilling is why we advocate for seismic monitoring of fracking operations to help identify these faults on the fly.

It is important to point out that the scientific community is more concerned about the potential for earthquakes from wastewater left over after fracking or oil and gas recovery in general. The wastewater is typically injected into deep reservoirs, often below the rock layer that is fracked to avoid contamination of much shallower drinking water. But that water pressure can leak into faults in the deeper, older rocks that are more faulted. The water can create more space between the two sides of a fault, making it easier for the fault to slip. There are some indications that the more water is injected, the larger the earthquakes could become, including some recent magnitude 4 and 5 events in Ohio and Oklahoma that caused some damage. Yet in the Appalchian Basin we have only found 4 cases where wastewater disposal is correlated with earthquakes, while over 300 deep injection wells do not cause detectable earthquakes. This leads us back to a similar recommendation: we should monitor to see which injection wells are problematic, and adjust the amount and rate of injection to limit the number of earthquakes.

Figure 2. Plot of showing the strong correlation between the number of earthquakes (blue) and wastewater injected (green) in the Youngstown case that eventually resulted in a magnitude 4.0 earthquake.

From a scientific perspective, the key advance in our approach to detecting earthquake induced by human activities is the development of a so-called earthquake fingerprint scanning technique. On TV shows like NCIS, they often show a fingerprint being scanned through a database to look for a match with a similar pattern. Our approach is similar in that we take the signals recorded from a particular earthquake and then scan through the database of all recordings looking for similar signatures. We use this method to find many smaller earthquakes that were previously undetected, we typically find 10 to 100 times more earthquakes than the official catalog of recorded earthquakes. These extra earthquakes are important for detecting unusual swarms of earthquakes occurring during nearby oil and gas related operations.

Video 1. Video explaining how the earthquake fingerprint scanning method we developed works.

For a List of Peer-Reviewed Publications of our Scientific Studies on Induced Seismicity: (Google Scholar)

For a Folder with PDF copies of our Peer-Reviewed Publications: (Google Drive)