For the last year, I and several others have covered the rise in seismicity in Oklahoma and Kansas. The earthquakes in these two states, coupled with earthquakes in Texas, Colorado, and Ohio, represent a significant increase in the background seismicity in the US east of the Rockies.
I’ve written a lot about this over the past year but here’s a recap in the off chance there’s someone here who hasn’t been paying attention. A sharp and substantial increase in seismicity in the central and eastern United States---half of it in Oklahoma ---began in 2008. It is almost certain that swarms in Ohio, Arkansas, Colorado, and Oklahoma have an anthropogenic cause and it is very likely that swarms in Texas and southern Kansas too have an anthropogenic cause.
In many cases, the anthropogenic cause is due to the disposal of wastewater either from hydrofracking or dewatering, the process used to extract previously inaccessible oil from fields considered to be no longer profitable. The salty briny water that comes up with the oil is reinserted back into the same formation.
That the process could be linked to some seismicity was and is settled science. Fluid injection increases the subsurface pore pressure. The increased pore pressure changes stress conditions that may be acting on subsurface faults that may be otherwise unknown because they have no surface markers. All continents have an overall stress and strain field due to their motions relative to each other, so the change in pore pressure on a fault that’s oriented in a favorable fashion may end up rupturing.
In most places, the seismicity that occurs is isolated and when the injection wells are shut down, the earthquakes eventually stop. This was seen in both Arkansas and Ohio and Ohio is one of the few states that actually has regulations regarding induced seismicity. Oklahoma, though, is a special case.
There seems to be no place in the United States where the scale of wastewater disposal is so vast, largely because the formations that yield up the oil that’s made billionaires out of people in Oklahoma are mixed with so much salt water. The salt water is then reinjected, billions upon billions of gallons of it, on a titanic scale. This sharply increased in 2009, and it neatly correlates with the rise in Oklahoma’s seismicity.
It’s dangerous now.
On November 8, 2011, an M5 earthquake occurred near the town of Prague. 24 hours after this quake, an even larger quake occurred, perhaps one that was one of the biggest in Oklahoma history. This quake destroyed a number of homes, injured at least one, and rattled the entire Midwest. A number of studies now indicate that the first quake was induced by almost 18 years of wastewater fluid injection—injection that sharply increased in 2009. The first quake than triggered the large and damaging mainshock and thousands of aftershocks that are still ongoing to this day. A 300 million year old fault system named the Wilzetta appears to have been activated.
Closer to Oklahoma City is the Jones Swarm. This swarm has been attributed to a truly immense amount of salty, briny fluid being injected into 4 wells along the downthrown side of the Nemaha fault system. By truly immense, I mean 4 to 5 million barrels per month, caused by the vast and immense growth in the oil extraction industry. Fluids can migrate in the deep subsurface and as they migrate, the increased pore pressure migrates with them. This has caused the swarm to migrate away from the wells a considerable distance—as much as 35 kilometers. The swarm appears to be migrating toward the Nemaha Fault which trends beneath the Oklahoma City metropolitan area, home to over one million people. This strand is roughly 50 kilometers long and is capable of hosting an M7 earthquake. The Nemaha itself isn’t oriented in the right way in the overall stress regime---but faults that are now illuminated by thousands upon thousands of earthquakes now are.
The swarms around Oklahoma City and off to the north near Stillwater have illuminated a complex tangle of subsurface faults. How this is done is via their focal mechanisms. What’s that? If you’ve ever taken a look at plots of earthquakes on a map, you may have noticed things that look like beach balls. That’s a focal mechanism. The “beach balls” depict fault planes and whether the faulting is strike-slip, reverse thrust, or normal. An analysis published in January of this year analyzed 3,639 quakes in Oklahoma, which you can read here. The study concludes a great number of the quakes occur on previously unknown blind faults that are relatively long, and relatively long is not something one wants to see. The study notes particular concern with the quakes occurring near Langston, another cluster near Cushing, and a cluster near Stillwater. All of these quakes in the aforementioned clusters are occurring on faults that are both long, therefore they can host large M6+ quakes, and optimally oriented, meaning they are both stressed and oriented with the continental stress field. In addition, the USGS’s National Seismic Hazard Map Project does not include human-induced seismicity (hazard maps are largely based on what has happened in the past—this is a bit of a problem for them according to a few seismologists out there). The hazard depicted on the most recent iteration of the maps, released in 2014, is underestimated for Oklahoma.
A presentation delivered at a Geological Society of America conference has great concern about this.
Disposal by subsurface injection of wastewater derived from energy technologies poses a risk of induced seismicity but, relative to the large number of operating disposal wells, few events are documented over the past decades. However, where large net volumes of injected fluids are involved, the potential exists for inducing larger seismic events. In Oklahoma, an exponential increase in seismicity coincides with a comparable increase in economic benefit from enhanced oil recovery (EOR) operations, from which an intrinsic by-product is up to an order-of-magnitude greater volume of saline wastewater. An initial (2008-2011) cycle of accelerating seismic-moment release (ASR) culminated in the Mw5.6 Prague earthquake. Since 2012 Oklahoma experiences a second ASR cycle, during which Mw4+ earthquakes - rare in 2013 - have become an almost weekly occurrence in the latter part of 2014. On a 0.02-yr analytical basis, extrapolation of the exponential ASR trend into 2015 and beyond indicates that an Mw5+ threshold may be breached by 2016. The spatial distribution of epicentres illuminates hidden faults, some favourably oriented for re-activation in the roughly WSW-ENE direction of maximum horizontal crustal stress. An epicentral alignment, extending SW-NE through the areas around Guthrie, Langston and Stillwater (GLS), is also recognizable in the pattern of aeromagnetic anomalies, and may be related to splay and transfer structures from the larger Nemaha-Wilzetta fault system. If a major part or the whole of the GLS structure is accidentally re-activated in a low-stress-drop regime by wastewater injection, it is capable of generating a significant earthquake in the range Mw5.5-6.5 or greater, for fault length in the range 20-70 km and fault slip 5-10 cm. The current seismicity gives rise to concern and restlessness in the general population, not easily allayed by calming rhetoric based on standard probabilistic seismic hazard and risk assessment (PSHA). Quantitative loss-modelling of reasonable worst-case (Mw6.5?) scenarios, and motivation of the population to prepare for them, may be psychologically and practically better. In this regard, Oklahoma hydroseismicity provides lessons for other regions (e.g., Karoo Basin, South Africa) where unconventional hydrocarbon development is contemplated.
(bold for emphasis, and it’s mine).
With all this bad news I was wondering if anyone has actually modeled what a large earthquake would do to central Oklahoma, including Oklahoma City. The answer is yes—but not recently.
Every state has an all-hazards mitigation plan and in each state, every county has one too. State plans often get aid from FEMA in their construction.
Oklahoma County (PDF) and Oklahoma City each have their own all-hazards plans and both consider earthquakes. (Tulsa's is here, in case you're curious.) The County developed a plan in 2013 and the City appears to have last updated their plan in 2006. Prior to 2009 Oklahoma had one known large quake source and that is the Meers Fault in the state’s southwest. They both considered a large quake centered on that as their Big One scenario.
Scenarios were run using HAZUS, which is a modeling tool developed by FEMA. HAZUS is able to calculate loss estimates, economic and human, from any disaster you can throw at it. These estimates are used in risk mitigation, emergency response and recovery and emergency preparedness. They’re a model, not a prediction, and are rife with uncertainties, but you can get a good idea.
Hazard Plans take a long time to develop—as soon as one’s released to the public the next one is already in draft. So Oklahoma City’s earthquake scenario was run in 2004. They modeled 5 earthquakes, 4 based on historical quakes and one an arbitrary M7 occurring on the Meers fault to the southwest. Only one was a local source. . In 1952, a moderately large quake (Mw 5.5-5.7) occurred near the city of El Reno. It was damaging enough that it cracked the dome of the Oklahoma State Capitol. The results of that model were a bit startling (but note that the HAZUS manual for earthquakes, which can be downloaded here indicates that damages from smaller than M6 quakes may be overestimated).
The city concluded in its 2004-2006 study (Appendix H in the plan) that an Mw5.7 quake, a repeat of the 1952 El Reno quake, would damage over 25,000 buildings (most of them homes). 847 would be destroyed. The scenario doesn’t destroy any essential structures and leaves the transport network intact. But it does model damage to utilities including at least 44 water main breaks, 35 sewer breaks and 38 natural gas breaks. Where those happen, you’ll have fire, and at least 44 major fires would break out. 25,000 households would lose their power. Depending on the time of day at least 27 would die (remember---this is a model with a tendency to overestimate with some data) and would cause in Oklahoma City alone, $2 billion (in 2004 dollars) in damage. It’s interesting that this local quake, a moderate one at that, appears to cause more damage to the city than the larger M7 farther away.
The county’s study, which did not include the city of Oklahoma City, ran similar scenarios based on “mean return period” quakes at 100 years, 500 years, and 2500 years. The 500 year quake was similar to the 1952 El Reno quake and the 2500 year quake was an M7 somewhere in the state, not necessarily in Oklahoma County. This scenario indicated in the county, almost a thousand displaced households and up to, depending on the time of day, 56 deaths, and $884 million in damage. This does not include the city of Oklahoma City (yes, I know this is absurd, but such is the jurisdictional BS that pervades the entire country) or the rest of the state and beyond, who would be affected by a quake of this magnitude. The county’s scenario does, in detail, go into building inventory and assigns a percent probability of sustaining damage to all major structures and this, for the 2500 year MRP quake, was not a small percentage. Communication infrastructure takes a particularly significant hit.
(I suppose it is worth noting here that tornadoes still remain the most destructive—as of now--- hazard in Oklahoma. The 2013 Moore tornado destroyed over 8,000 homes alone.)
The GSA talk linked above stated that it’s time to update those scenarios because of something called “Accelerated Seismic Moment Release.”
This is based on observations elsewhere that a large earthquake is preceded by a lot of smaller ones. There’s some doubt about the hypothesis. Unfortunately, earthquakes can’t be predicted—even ones induced and/or triggered by people. At best, they can be forecasted---and predictions and forecasts are two different things. Predictions are conditional statements about the future (“this will happen.”) Forecasts are judgmental statements about a possible likely future (‘this might happen if these things happen”).
But it’s sobering to use Google Earth Pro (now free!) and fly around Oklahoma City. Like most places, there’s a 3d model for most large structures in the city. Flying around the densest part of the city (downtown) it’s sobering to see large concrete multi-storied structures that could possibly be heavily damaged in a large quake centered on one of the optimally oriented strands of the Nemaha that run beneath the city. A neighborhood called “Bricktown” has lots of brick facades—these would be in the street. “Driving” through the low-density sprawl surrounding the business district using Google Street View one sees many homes with brick facades and chimneys and these will come down. Apartment buildings with soft first floors—these too will collapse as Californians are all too aware. I suspect the brand new glass-clad Devon Tower would survive just fine---just without all its glass. I also wonder how a large structure like the Chesapeake Arena would survive. Both Devon Energy and Chesapeake are oil industry giants in the state of Oklahoma. And I haven’t even begun to discuss dams. The state, county, and city hazard mitigation plans make note of almost 2 dozen high-hazard dams and, although this is perhaps a limitation of the HAZUS model, no scenario makes note of any failure of these structures. Their failure is discussed in other sections of the plans, so one can get an idea as to how bad it could get if any, especially a large dam far upstream on the N. Canadian River, fail.
A real-life example of what a moderately-large quake beneath a major but not prepared city can do is Christchurch, NZ, where in February of 2011 a M6.2 quake killed almost 200 people and did catastrophic damage to the city, so much so that parts of the city will have to be abandoned and the cost of rebuilding likely will have long-term effects on that country’s economy. This quake was part of a swarm that began in the previous year and finally appears to have mostly tapered off. New Zealand is seismically active and is considered to be a leader in preparedness, and these quakes rather shocked them.
There are quite a few dire FEMA studies out there, for any disaster you can think of, that cover many states. I find this is a limitation of many all-hazard plans---they don’t consider that regions are affected, not just one locale. I dug through FEMA’s site—lots of studies on what a major quake will do to the region to Oklahoma’s east (OK would be barely bothered). At present, none for Oklahoma.
This may sound like fear-mongering but what the talk linked above suggests, and what I’m suggesting, that it is time to run such a scenario, if someone somewhere isn’t doing so already. Thousands of miles of critical infrastructure from oil and gas pipelines to major interstates and major railroads cross the state and region. We have a pretty good idea as to what an M7 will do a 7 state region centered on Memphis. We don’t for Oklahoma, and that’s not acceptable. I am on a couple listservs about the New Madrid region and I’ve grown to almost resent the yearly drills done for that region. They’re very important, but they’re for a hazard that’s forecasted to be a couple centuries off in the future if they even recur).
I feel the growing concern for Oklahoma is valid. There needs to be a major preparedness drill because the hazard doesn't just include Oklahoma, it includes north Texas and a great deal of Kansas too.
It’s equally unacceptable that the state’s government has its head in the sand as to the glaringly obvious cause. I rather resent the calls for Oklahomans to purchase earthquake insurance (despite an indication that the insurance industry will not pay out because the quakes aren’t “natural”) .
Everyone should have a preparedness and disaster kit and while I think the global ShakeOut movement is great, I can’t help but feel cynical when Gov. Mary Falin declares October 16th “Earthquake Preparedness Day” while her cabinet and the state legislature continues to hem and haw as to the reasons why this preparedness day is now necessary. And I have to laugh that finally—FINALLY—as of today, the Oklahoma Geological Survey states that “Based on observed seismicity rates and geographical trends following major oil and gas plays with large amounts of produced water, the rates and trends in seismicity are very unlikely to represent a naturally occurring process.” I guess they couldn't stay silent anymore.
I also have to state that I’m willing to entertain any hypotheses the oil industry is willing to put forward—provided they aren’t bullshit and I’ve read some that are bullshit. So if they want to say “this isn’t our fault” there are a lot of ways to go right ahead and prove that. If, in prehistory, massive swarms of minor quakes led to a series of very large ones in central Oklahoma, there’d be evidence left behind even if the causative fault or faults did not break the surface. This is, despite the previously linked Dr. Stein of Northwestern University, why the USGS continues to rate the New Madrid Seismic Zone as very hazardous. Ancient very large quakes left considerable traces across many states, from Louisiana to Indiana over the last 10,000 years. Paleoseismic studies are one of my favorite type of study to settle in with and give a good deep read. So go, Devon and Chesapeake, find me some sandblows. Find me another fault scarp like the Meers. Show me the evidence that this is not your fault.
I suspect they won’t be able to.
3:27 PM PT: The State is giving some indications it's doing a bit more than hem and haw. They've set up this portal today: http://earthquakes.ok.gov/ and the state geological survey's statement is linked in the diary.