Last November, a M5.0 quake caused some damage in Cushing, Oklahoma. A number of folks at the time were relieved that there wasn’t any noticeable damage to the nation’s largest oil storage facility. This was only a few months after the Oklahoma Corporation Commission ordered a cutback in disposal of wastewater in injection wells. Since then, seismicity has mostly quieted down, but it seems that recognition of the scale of the hazard has been seeping into the awareness of a broader part of the media, leading to a lengthy piece in Politico Magazine on the potential disaster lurking in Cushing from facilities not really designed to survive an earthquake. While most of the stories of earthquake hazards in Oklahoma have been more focused on falling chimneys and old brick buildings, this piece exposes a pretty critical flaw in Oklahoma’s infrastructure.
So we will hope that there isn’t another unrecognized fault slowly being lubed up under Cushing. But remember, the largest events from the infamous Rocky Mountain Arsenal injection adventure in the 1960s came more than a year after injection was totally stopped. Oklahoma hasn’t stopped injecting fluids, and the volume of water injected so far dwarfs anything that happened in Denver in the 1960s…
Its been awhile since Oklahoma earthquakes made news and so it seems timely to look in on the Sooner State to see how things are going.
Last we looked in, numbers of earthquakes were down but the moment release was still pretty high. Predictions from Stanford late last year were that the decreased injection of wastewater would lead to a decrease in earthquakes over the succeeding five years. The USGS, in contrast, has continued to note that the decrease in the number of events does not mean a decrease in damaging earthquakes.
So far, the news is good. Not too surprisingly, the number of earthquakes continues to drop:
So that continues the trend from 2016. What about moment release? Well, given the absence of news reports, you’d guess there is a decline there, too, and you’d be right:
And, indeed, 2017 has been dead quiet moment-wise as well.
Does this mean that the seismic risk is now gone? Well, no. That M5.7 earthquake in late summer last year was on an unrecognized fault. The fluids migrating in the basement could encounter another critically stressed fault and trigger a significant earthquake. But for now, this is good news for Oklahoma residents.
With 2016 coming to a close, GG thought we might want to see just how things are shaking out in Oklahoma, home of the great induced earthquake experiment. And there is something for everybody, depending on how you want to look at it.
For the optimists hoping that Oklahoma’s actions to slow wastewater injection will end the plague of induced earthquakes, we have plot number one: number of quakes with a magnitude of 3.0 or higher by month:
The rate of such earthquakes dropped from nearly 4 a day in January to about one a day this month. And you could hope that this had something to do with this:
The 25% reduction during the year in the rate of injection in the area where triggered seismicity has been observed might be responsible for this. But there are other things to watch as well. First, these are still pretty high volumes of water going back into the Arbuckle, and all the water that went down earlier is still making its way through the subsurface. Second, presumably a lot of produced water is going to other wells, either in the Arbuckle outside the area of interest or into other formations. Third, a decrease in the number of M3+ events is not the same thing as a decline in seismic moment:
The 9/3/2016 M5.8 Pawnee, Oklahoma earthquake put a big damper on any celebration of a decrease in seismicity. The overall moment release of 7.8 x 1024 dyne cm is the largest single year moment release in Oklahoma history. As we noted before, this isn’t unexpected: the Rocky Mountain Arsenal sequence in the 1960s produced its largest quakes after the injection ended.
So we enter 2017 on a note of caution. If you bought earthquake insurance in Oklahoma, don’t let it lapse just yet. You might get shaken a bit less often, but when you do get a quake, it might still be pretty big.
P.S.: there are a couple of nice visualizations out there. Tulsa World put together an interactive map a year ago showing how produced water injection was varying over time and by county. The Oklahoma state government has an interactive figure with recent earthquakes and disposal well locations.
Well, it appears that the state of Oklahoma finally bought into the connection of earthquakes to deep injection wells as the recent M5.6 earthquake led them to shut down injection wells in the vicinity of the epicenter [and once again we learn the national media still cannot discern between fracking, which is not the cause here, and injection of waste water, which is the likely culprit]. Interestingly, there are two views on how Oklahoma seismicity is varying: Dan McNamara of the USGS argues that seismicity is still on the rise, while Oklahoma Geological Survey director Jeremy Boak is quoted by the Tulsa World that “I still expect to see declining figures over the rest of the year just because we’ve decreased the (wastewater) injection so much.”
Given how long the Oklahoma survey dragged its feet on acknowledging the problem, their credibility is kind of at a low point. McNamara in November said that more M5s were likely, and two more have happened since. McNamara made a plot of seismic moment over time that is pretty damning:
The big decrease in seismicity Boak was excited about is the somewhat shallower slope of moment increase in early 2016, a decrease now obliterated by this latest quake.
The problem is that fluid injection of this magnitude over this amount of time has probably not reached any kind of equilibrium yet. The overall upward concavity of this plot suggests that we aren’t at the end of increasing rates of moment release. Hopefully it will come as a boatload of small-impact M4s and low M5 events, but M6 events don’t seem implausible. If you look at a much smaller example, the likelihood of earthquakes continuing for decades is substantial–even if injection stops.
Back in the 1960s the Army injected wastewater at the Rocky Mountain Arsenal into basement. This caused a bunch of earthquakes and eventually the injection was stopped–but two years later some of the largest quakes in the sequence happened. At the time the interpretation was that the pressure wave from the injection was propagating outward and so could have a substantial time lag. Regardless of mechanism, it should concern Oklahoma residents that in a similar case with much, much smaller volumes of water being injected that earthquakes continued long after injection ceased.
It is great that the Corporation Commission in Oklahoma has acted to shut down a number of injection wells. Too bad some of this didn’t come before the billions of barrels of produced water were injected into the Arbuckle Formation. We will see if this closing of a barn door caught the horse or not. The problem may be that the pasture gates need closing too: the production of oil is not likely to shut down at the same rate as injection well capacity; produced water will probably be rerouted to wells that have not yet been shut down. And while many wells probably pose no risk of inducing earthquakes, some probably do. So this might simply migrate the problem even farther afield.
One reality is that the duration of time needed to really see if this helps–probably on the order of years at this point–is almost certainly beyond the ability of government overseers to keep operators from applying political pressure to resume operations at some level. The only really good solution is some kind of processing of these waters so they can be released at the surface, but such purification is expensive and would require creation of infrastructure that doesn’t yet exist.
Well, of course, there is another solution: quit pumping oil. Don’t hold your breath wait for that one. And if you live in Oklahoma, you might just want to see how much that earthquake insurance is. And find those webpages Californians have perused for years on how to make your house more quake-proof.
First, there was Oklahoma’s Senator Inhofe throwing snowballs in Congress to attempt to show that climate change wasn’t happening (the Daily Show slugged it Grumpy Cold Men). (“Embarrassing” shows up in many headlines on this antic).
Then there was the revelation by Environment and Energy Publishing that strong arm tactics from the oil industry kept the Oklahoma Geological Survey from openly identifying wastewater disposal wells as the cause of earthquakes in Oklahoma for many years. Doesn’t exactly make the OGS look good (and frankly, at the time many seismologists outside the state were wondering what the OGS was doing). A Tulsa World article covers this as well.
The good news is that the largest earthquake in Oklahoma this past week was only a 3.4. (California actually managed a 3.7, though Kansas was in the lead with a 3.8. Oklahoma did retain a lead in number of earthquakes larger than 2.5).
A few quick notes:
In contrast, the Greeley earthquakes died down while the injection company stopped injecting and plugged the part of the well that was directly connected to a fault. But as they resumed injecting, a M2.1 showed up, so this probably isn’t the end of the story…
And finally we get the odd news from USGS scientist Sue Hough (why does the WSJ deny her her doctorate?–she is quoted as “Ms. Hough”)) that induced earthquakes seem to cause less shaking for a given magnitude than tectonic earthquakes (and by the ways, if you see headlines including the phrase “fracking-induced earthquakes” then you know the headline writer is ignorant, and if it is in the article, then the writer is ignorant; these earthquakes are induced by wastewater injection). Something seems kind of fishy, but as the article doesn’t seem to be online yet (presumably will be posted later today); right now this seems most likely to GG to be because all the attenuation models are keyed for earthquakes in the basement rocks and not in the more attenuative sedimentary rocks, though there are hints in some of the online stories that Dr. Hough (we’ll give her her doctorate) proposes that the stress drop is lower because of fluid pressures, which in turn reduces the peak accelerations. Anyways, hard to be sure when working from an AP article; will update when the BSSA article goes online.
Update is in the full post. Read More…