New USGS Report Finds Risk of Damaging Earthquakes from Induced Seismicity is Low
For the first time, the United States Geological Survey (USGS) has released maps that illustrate the one-year outlook for the potential of both natural and induced seismicity in the central and eastern United States.
The map has already produced some misleading media coverage incorrectly linking induced seismicity to fracking as well as exaggerating the risk level of induced seismicity from wastewater injection.
But not only does the report and accompanying press release clearly state wastewater injection is primary cause of induced seismic events, rather than fracking, it also illustrates that the risk of damaging earthquakes from induced seismicity is low.
Here are three facts to know about USGS’s new report and maps.
Fact #1: USGS reiterates that fracking “only rarely” the cause of felt earthquakes
The USGS makes crystal clear in its press release that hydraulic fracturing very rarely causes felt seismic events.
“Many questions have been raised about hydraulic fracturing—commonly referred to as ‘fracking’—and USGS studies suggest that this process is only rarely the cause of felt earthquakes.”
In fact, fracking is never directly referenced in the report. This reinforces earlier statements by the USGS, which released a document last year to clear up the misrepresentation in headlines that too often link fracking to earthquakes:
“In the United States, fracking is not causing most of the induced earthquakes. Wastewater disposal is the primary cause of the recent increase in earthquakes in the central United States.”
Of course, a vast majority of seismicity in the central U.S. in recent years has occurred in Oklahoma. Of the 2,226 3.0 M earthquakes in the central United States between 2009 and 2015 identified in the study, 1,708 (77 percent) have occurred in Oklahoma since 2009. Expert after expert has reiterated that wastewater injection is the likely cause of Oklahoma’s spike in earthquakes.
For instance, Stanford geophysicist Mark Zoback, who has conducted numerous studies on earthquakes in Oklahoma, recently released a video explaining that earthquakes in Oklahoma have nothing to do with hydraulic fracturing:
“What’s happening in Oklahoma is unrelated to hydraulic fracturing. It’s unrelated to hydraulic fracturing flowback water. It’s caused by massive injection of produced water.” (marker 2:52)
USGS seismologist George Choy reiterated Zoback’s point in an Gizmodo.com story on the study.
“Most of the water does not come from fracking, it just comes from regular oil and gas.”
Dr. Matthew Hornbach, a scientist at Southern Methodist University (SMU) made similar comments last year regarding media coverage of North Texas earthquakes that were linked to wastewater injection:
“We’re not talking at all about fracking. In fact, it’s been driving us crazy, frankly, that people keep using it in the press.”
Fact #2: Very few injection wells have been linked to induced seismicity, and the risk from these wells is low
The report clarifies that although wastewater injection is the primary cause of induced seismicity, the number of injection wells tied to induced seismicity is marginal.
“Wastewater disposal is thought to be the primary reason for the recent increase in earthquakes in the CEUS (Central United States). While most injection wells are not associated with earthquakes, some other wells have been implicated in published scientific studies, and many states are now regulating wastewater injection in order to limit earthquake hazards.”
A 2015 EID report based on data from the USGS and peer-reviewed studies, found that fewer than one percent of wastewater injection wells has been linked to induced seismicity.
As the following map illustrates, the USGS report found risk levels for damaging induced earthquakes of one percent or less for most areas in Texas, Colorado, New Mexico and Arkansas, which is the same risk level assessed for states such as Minnesota, Iowa, Nebraska and other states with little to no oil and gas production. USGS found only a 2-5 percent risk level in very small areas of New Mexico, Colorado, Texas and Arkansas.
The USGS pointed out that the risk level illustrated in the western states shown on to the left on the map above (most notably California) is based on the presumption of naturally occurring earthquakes rather than induced earthquakes.
Only a very small portion of south-central Kansas was identified as an area with a 5-10 percent risk of experiencing a damaging induced earthquake. It is important to note that just 1.6 percent of Kansas’ 5,000-plus disposal wells have been potentially linked to induced seismicity, and as the USGS report notes, Kansas regulators have recently taken steps to extend reductions of wastewater injection in Harper and Sumner counties, areas where induced seismicity has been an issue.
Areas of Oklahoma, not surprisingly, make up a vast majority of the map in which the USGS believes there is a 5-12 percent chance of a damaging induced earthquake.
But for perspective, even when considering the highest possible number of injection wells that regulators have been watching closely, the vast majority of injection wells in Oklahoma are still operating without seismicity. And regulatory measures continue to be put in place in the Sooner State to address injection volumes in areas the USGS highlights. The Oklahoma Corporation Commission recently released a new regional seismicity response plan covering 5,200 square miles and affecting 406 disposal wells in central Oklahoma that will reduce annual wastewater volume disposed in the area by 40 percent below 2014 volumes. The OCC announced a similar plan in western Oklahoma early this year, with the two regional plans covering 640 disposal wells and 10,000 square miles.
The OCC has also expanding its “area of interest” (AOI) to include 118 additional Arbuckle disposal wells in areas that have not yet seen earthquake activity. It is believed the Arbuckle formation, which sits below producing formations, may be in hydraulic communication with the crystalline basement and therefore be re-activating previously unknown faults. The OCC’s recent efforts are just part of a continuing response from regulators and industry to address the issue of induced seismicity in the state.
Fact #3: Some areas with prior history of induced seismicity identified as low hazard areas
Interestingly, a handful of the 21 areas in which the USGS says scientists have documented potential induced seismicity are not highlighted as significant hazard areas on the USGS’s new map.
“Induced earthquakes have occurred within small areas of Alabama, Florida, Ohio, Pennsylvania and Utah, but a recent decrease in induced earthquake activity has resulted in a lower hazard forecast in these states for the next year.”
Areas of documented potential induced seismicity are shown in the USGS map below.
But the areas referred to in documented above in southern Alabama, Florida, Ohio, Pennsylvania and Utah are not indicated as increased risk areas in the USGS’s earthquake forecast map shown below.
In fact, areas such as the Bootheel of Missouri – where no induced seismicity has been suspected – are considered higher hazard areas for earthquakes due to natural conditions than the areas cited in the above paragraph.
“For example, the New Madrid Seismic Zone near Memphis has experienced a higher rate of natural earthquakes in the past two years, leading to a slightly higher hazard potential in small portions of Arkansas, Missouri, Illinois, Kentucky and Tennessee.”
Despite hyperbolic headlines, the new USGS map and report doesn’t really tell us anything we didn’t already know about induced seismicity. We already knew that wastewater injection – not fracking – was the likely cause. We already knew that induced seismicity was rare in most areas of the central United States, and that the potential for damaging quakes was minimal. And we already knew that regulators in areas in which induced seismicity is most prevalent – Oklahoma and southern Kansas – are working to address the issue.
The USGS also acknowledges that its map is anything but a forecast for certain earthquake activity.
“Of course there is a level of uncertainty associated with this and all hazard maps, as we are still learning about their behavior and can only forecast with probability—instead of predict with certainty—where earthquakes are likely to occur in the future. Testing these maps after a year will be important in validating and improving the models.”
That said, those who say the extreme measure of banning wastewater injection (and the U.S. oil and gas industry, effectively) based on this USGS report should consider what Bill Ellsworth of the USGS has said about the issue of induced seismicity in the past:
“What we’ve found is there is a link between disposal of waste water and earthquakes. And in many of these cases, it’s been fixed by either shutting down the offending well or reducing the volume that’s being produced. So there are really straight-forward fixes to the problem when earthquakes begin to occur.”