Some of Oklahoma’s most-powerful earthquakes in the past year gave Kansans a shake in the past week, and a research geophysicist says it is safe to assume these quakes were due to wastewater injections in Kansas and Oklahoma.
“This is not particularly surprising — we’re not surprised by this,” said Justin Rubinstein, who is also the deputy chief of the United States Geological Survey's Induced Seismicity Project.
While the cause of these quakes has not been confirmed, Kansas Geological Survey senior scientist Rick Miller agreed that they were likely “human-induced earthquakes.”
“There’s no way to be absolutely confident, but there’s no question that it’s very likely that the injection of water has been a catalyst in the increase of earthquakes over the last 4-5 years," he said.
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Since the spike of potentially human-induced earthquakes began shaking the borders of Oklahoma and Kansas, tightened restrictions on wastewater injections have been put into place.
But the earthquakes haven't stopped.
“Even if you stopped all injection immediately, earthquakes will persist — probably for years,” he said. “Just because you stop it, it doesn’t mean you change the conditions.”
However, Rubinstein said that with tightened restrictions on the underground injection of oilfield wastewater in Oklahoma and Kansas — in addition to less oil production — there has been a gradual trend of fewer earthquakes that can be felt.
Should we expect more quakes?
“There’s no question — we’re going to continue to have earthquakes,” Miller said.
As for how many earthquakes, and at what scale, both Miller and Rubinstein said it is nearly impossible to predict what kind of earthquakes Kansans may experience.
“In general, the earthquake rate has been going down, so larger earthquakes are likely going down with it, but I wouldn't say the possibility (for larger quakes) isn’t there," Rubinstein said.
Rubinstein said earthquakes tend to cluster in place and time, which is likely what Kansas and Oklahoma are experiencing right now.
But neither Rubinstein or Miller can predict if the cluster will continue.
So far in 2018, five earthquakes with a magnitude of 2.5 or above have been reported in Kansas by the USGS. In most cases, a magnitude of 2.5 is needed for a local quake to be felt.
In 2017, 120 earthquakes with a magnitude of 2.5 or above were reported. And from 2014 through 2016, 427 of those quakes were reported.
To put those numbers into perspective, 33 earthquakes with the same criteria were reported to the USGS from 1977 to 2012.
Many of the earthquakes were reported in south-central Kansas, including Sumner and Harper counties. This includes the largest recorded earthquake in Kansas history — a 4.9 magnitude earthquake in 2014, which was likely connected to injected wastewater, according to a study by the USGS.
This week’s quakes
The March 4 quakes, reported at 4.2 magnitude, were the strongest in Oklahoma since September, when a magnitude 4.3 struck in the northwestern part of the state, Oklahoma Geological Survey seismologist Jacob Walter told the Associated Press.
The quakes were felt by those in south-central Kansas.
“The key thing to keep in mind is, as alarming as the earthquakes are, in Kansas they haven't escalated to significant damage levels,” Miller said. “They are a nuisance and unnerving, but the ground shaking is very minimal ... and it’s good to know what the source of these things are."