People who drill deep holes in the ground and shove or pull fluids through them have been causing earthquakes for at least 80 years. But few if any have been as big as the magnitue 5.6 quake that busted chimneys and scattered goods across the floors of stores in Oklahoma on Nov. 6, 2011. From the start suspicion was raised by the epicenter's location – right where an oil company has been injecting wastewater deep into the underlying rock.
This is not fracking for either natural gas or oil, by the way. It also is not a carbon capture and sequestration test to see if CO2 can be pumped way down yonder where it is unlikely it will leak up, at least not much. But the basic geophysics are similar enough that the new paper's conclusion will surely reverberate in public hearings whenever a new fracking field or CCS program is before regulators and watchful activists. The paper is in Geology, its authors are at the University of Oklahoma, Columbia U, and the US Geological Survey. The question regarding news coverage is whether the fundamental ambiguity of any one quake's cause is properly reflected, and whether the public gets a proper sense of the history and larger context of the conclusion that the well drillers likely done busted them chimneys.
We also have possible irony on offer. In the 1930s and 40s a series of earthquakes in California's Wilmington oil field near Long Beach badly damaged the drill rigs and associated oil lines. Not to mention damage to nearby streets, wharves, buildings, and bridges. The quakes were blamed on the dramatic subsidence of the field – 30 to 45 feet near the center of the large, resultant bowl – and on abrupt cracking of strata. So the oil companies started injecting waste water into the oil-bearing sand to replace the oil they took. Subsidence pretty much stopped. (old history paper here). Replacement of oil pumped up with waste water pumped down is now standard industry practice in areas prone to subsidence. So one wonders, while just guessing and having not tried to report this story oneself – was the Oklahoma injection program part of a tactic historically rooted in efforts to prevent quakes from oil operations? Or was it just a convenient way to get rid of some foul water?
The quakes – there were many of them aside from the main shock – if the paper's thesis is correct were a cascade of ever-larger ruptures. They started with a small fault near the drill site and riffled via a network of faults through more distant, tensed terrain. That means the quake's energy was not at all entirely from the built-up pressure of the injection. But that injection may have been the seed for release of preexisting stress – meaning that something like this was probably eventually going to happen anyway. But proximate causes that determine when it occurs are the ones that people care about and leave them thinking of filing suit.
It is some interest if not significance that coverage all gives the quake's magnitude as 5.6. But the Columbia press release as well as the one from the journal (see Grist br;pe) have it at 5.7. Dunno if that's moment, Richter, or some other among the confusingly similar scales of magnitude in use.
Anyway…
Stories:
- AP – Seth Borenstein: Report: Big OKLA. Quake in 2011 Likely Man-Made. ; Excellent on the context of this quake and the history of other but much smaller quakes. It acknowledges that state geologists think there is so much such injection in OKLA that a quake anywhere can't be too far from a well doing that kind of work. So, coincidence is easy to imagine. Borenstein notes that drilling, and waste water injection, has been underway in the state for decades, too. But other sources tell the reporter that the paper makes a strong case. This is solid wire service (ie, major outlet) reporting with some history and some back and forth.
- LiveScience via NBC.com News – Tia Ghose: Oil Extraction wastewater caused Oklahoma's biggest quake; One suspects a question mark belonged on that hed. But the lede confirms the lack of prevarication, declaring that the drilling=quake thesis is now confirmed. And the story quotes one authors as saying it is "shocking" that a quake big enough to be felt so widely hit Oklahoma, out there on the continental craton. The story includes a line saying that areas are more prone to such seisms if the injection site is not very permeable. Is that true? Could be, just never read it before.
- Dept of Investigation and Scoops – KJRH (NBC Affiliate) Marla Carter (Feb. 20, 2012): Could oil exploration be the cuase of earthquakes in Oklahoma ; This story (with video) from a year ago shows how well some media dug into the drilling and quake link. Much of her reporting was on fracking and clearly-related, smaller quakes in Arkansas, not Oklahoma. The station has out now an on camera report by Carter referring to her earlier enterprise reporting and to the new paper. Kudos.
Grist for the Mill: Columbia U. Lamont-Doherty Earth Observatory Press Release; Geology Press Release ; paper abstract;
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