At least one northwest Oklahoma resident found damage after an earthquake rattled the area early Monday.
Megan Heger, of Enid, discovered a crack in her ceiling between her dining room and kitchen. There also is a crack in the ceiling above a cabinet in her kitchen, closest to the dining room.
"It's not real big but certainly wasn't there before the earthquake," she said, referring to the crack between her dining room and kitchen. "This appears to be the only visible damage inside or out. I had some stuff fall on its side that was sitting upright on my washer and a couple books fell from the top of the dryer onto the floor. Nothing else was damaged and we've tried to 'quake proof' as much as possible, just in case we do get a big one.
"Our fridge is an older model and the door opened enough that a couple plastic condiment bottles fell out."
The quake, at 3:49 a.m. Monday, originally was reported to be a 4.5 magnitude, but U.S. Geological Survey has since upgraded it to a 4.7 magnitude. The magnitude may be revised further in the future, Oklahoma Geological Survey Director Jeremy Boak said Tuesday.
OGS calculated the earthquake was 4.2 magnitude.
"We're just in the process of reconciling that to try and have a conversation with (USGS) about what exactly that's based on, how many stations. We actually have a larger network," he said. "The (USGS) uses only its stations, which are five or so close by. We're using about 30. So, questions about depth and things like that get sensitive, and it sometimes takes a little while to shake out the actual magnitude for these earthquakes."
A 4.7 magnitude quake recorded on Nov. 19 is "pretty stable" now, making it the largest earthquake in Oklahoma since some recorded in 2011, Boak said. Another 4.7 quake was recorded Nov. 19 in Alfalfa County.
"There are uncertainties with all of these things," he said. "It's about trying to get the best estimate and sometimes it takes some refinement."
In January 2014, there was a fairly large pulse of earthquakes in Grant and Alfalfa counties, he said. At one point, those counties had a 45-day average of 2.5 earthquakes a day.
"It then tapered off, very substantially," Boak said. "And then pulsed again in July and then started down again. And now it's come back again. So this is really in the nature of earthquakes, that they come in pulses, that they come in groups, that the rates at which they happen are erratic, highly variable.
"We're just beginning to understand some of those things about that. I have a feeling that kind of pulse of earthquakes has seen less attention, in part, because it's more rural, so they took less notice of it."
Boak said he thinks Oklahoma Corporation Commission has moved forward in a "kind of staged and careful manner."
"What we're still trying to understand is the relationship to the amount of (wastewater) injection. We've only got partial data for this year. We did look at 81 wells that were injecting into the Arbuckle and what we'd seen was a one-third drop in injection, but a lot of that was concentrated in a fairly specific number of wells," he said. "Out of the 81 we were able to get a full record for, I think, about half of it was just three different wells that decreased very substantially."
USGS analyzed some magnitude 4 earthquakes in the Cushing area in 2014, he said.
"What they pointed out was that, at that time, the Corporation Commission reacted by asking someone else to shut-in. They then relaxed that restriction and injection started again, and then we had another pair of magnitude 4 ... (quakes) in the Cushing area. So, we still think there's a strong relationship there," Boak said.
The OCC's approach has resulted in addressing approximately 600 wells. The response has been relatively careful and cautious, "trying to pay attention to events as they happen," he said.
"So, to say that this state is doing nothing just shows a lack of understanding, a lack of attention, to what's actually being done," Boak said. "But, should there be more? It's a little hard to tell because, in fact, earthquakes are erratic in their behavior. While we attempt to say, 'OK, let's act where it's probably happening,' is probably a good idea, a total shut-in — as I understand it from the seismologists — a total shut-in would be likely to produce a kind of negative pressure pulse that might also induce a set of earthquakes."
He said the careful and staged response is "probably a good way to go."
If all injection wells in the state were to be shut-in, they would go from applying sort of steadily increased pressure to having the pressure pulse dissipate. As it dissipated, it might produce a few earthquakes itself, Boak said.
There has been a 25 percent decline in earthquakes — which has been eroded some by the pulse of quakes in November — since July, he noted. One possible explanation is "it was a lull."
"That seems to have been what was going on, at least in those two counties up there," Boak said.
There is a substantial team at OGS working on the issue, he said.
"It's just not an easy one to address. It's exciting to work on this because it truly does affect people's lives but, unfortunately, science can't move as fast as the news cycle," Boak said.
It is unusual to tie earthquakes to specific injection wells in Oklahoma, he said.
"It's sort of a big pattern of injections happening in this area at fairly high levels and earthquakes are happening in this area at fairly high levels. And that's partly a matter of the geologic features of the area, something we're just beginning to develop a good description of," Boak said.
He's looking to have staff members look at month-to-month injection rates.
"We think we see a decline but we'd like to see enough data to make sure that that's uniform, and is that partially what's responsible? Is it all about different pulses of earthquakes? What are the forces that are driving this? And we're scrambling to try and figure those things out because it does matter," Boak said.
On Tuesday, Gov. Mary Fallin announced she was forming a work group to study ways to recycle or reuse water from oil and gas operations, rather than injecting it into the ground.
The group will discuss the issues associated with treating the water for industrial uses or crop irrigation, Fallin said. J.D. Strong, director of Oklahoma Water Resources Board, will be chairman. Other members will come from agriculture, power generators, public water systems, oil and gas industry, Oklahoma Department of Environmental Quality and Oklahoma Corporation Commission.