The USGS is studying the data and looking at earthquakes that have happened in Oklahoma. While researchers can’t pinpoint a cause at this time, the Saturday 5.6 Earthquake near Pawnee has some similarities to the 2011 quake that shook up Prague.
Daniel McNamara, a Research Geophysicist with USGS, says the recent earthquake was not on a fault known by the USGS. Instead, it happened on a fault perpendicular which intersected the fault. Based on aftershock patterns, this one is an unknown fault that has now been activated.
“At this point, we don’t know if it is related to waste water injection, but it’s very similar to other sequences that have been, so it’s highly likely,” said McNamara.
McNamara said, however, this earthquake also looked natural in some ways based on the before-shock behavior. There were only a few two to three magnitude earthquakes leading up to the big shake. This is compared to 2011 in Prague when there were three and four magnitude earthquakes before the major one.
A Big Aftershock Could Be Looming
There have already been dozens of aftershocks near Pawnee since the Saturday quake. Most of them are magnitude three or less; some that people can’t even feel.
McNamara is warning Oklahomans that something bigger may be on the way.
“There could be a high-magnitude four aftershock, so people should be prepared,” McNamara said.
McNamara said the number of damaging earthquakes in Oklahoma since 2011 is unusual.
“Magnitude fives occurred in Oklahoma maybe once every 50 to 100 years, naturally occurring earthquakes,” said McNamara. “But in the last five years, you’ve had three earthquakes over magnitude 5.”
In 2011, a 4.8 magnitude aftershock happened two days after the Prague quake. He said something similar may happen in Pawnee.
“Look at the FEMA webpage and learn what to do in case of an earthquake,” said McNamara.
FEMA outlines the drill to drop, cover, and hold on until the shaking stops.
The Largest Earthquake In Oklahoma History
McNamara confirms Saturday’s earthquake is the largest earthquake in Oklahoma history, even though the magnitude was initially rated the same as the 2011 earthquake in Prague.
He said magnitudes are rounded numbers. The Pawnee temblor was larger because the energy level of the earthquake was higher.
“It’s 10 percent more than the Prague 5.6, so that was the largest earthquake you’ve had so far. This one is slightly larger,” said McNamara.
McNamara said they may boost the magnitude of Saturday’s earthquake up to 5.7.