USGS geophysicist: Edmond fault could produce large earthquake

FULL INTERVIEW: USGS Seismologist warns of larger Oklahoma quake

A USGS research geophysicist says the recently rediscovered fault under Edmond could produce a quake as large or larger than the Prague quake of 2011 that registered a 5.6 on the Richter scale. It's the state's largest on record.

Daniel McNamara, who works with the National Earthquake Information Center in Golden, Colorado, says the Edmond fault is very similar to the one near Prague.

"It's an old fault that hasn't been active for quite some time," McNamara said. "We identified it on a geology map produced by oil and gas industry consultants."

McNamara says it also exhibits similar events that led up to the record 5.6 quake.

"We look at the surface area of the fault, the length and the depth to calculate a possible maximum magnitude, and that fault could definitely produce an earthquake as large as the Prague 5.6 in 2011," McNamara said. "And again, it has similar characteristics, it's oriented the same way, it's had magnitude 4 foreshocks, the 2011 had two magnitude 4 foreshocks, so when we see magnitude 4's on faults that could host a larger earthquake, we become concerned."

"This is no way a forecast to say 'it will happen', but people should be aware that it could," McNamara said.

McNamara says it could be larger, but since none have been bigger, it's limited to observed quakes.

McNamara says there are a few pieces to the earthquake puzzle, including oil and gas activity, the fault and the recent winter storm.

He says the added extra pressure of two additional feet in Lake Arcadia could have enough force to cause a quake, but it alone isn't causing quakes.

"The Arcadia Lake reservoir had a two-and-a-half feet of water added to it in a two-day period that correlates temporally pretty well with the Edmond sequence, so it's possible there are many things contributing."

He adds there's a lot that seismologists are still looking at.

"Where are you most likely to generate an earthquake, and in the case of wastewater injection, and in reservoir management, they're both human activities that can be managed to potentially avoid large earthquakes," McNamara said. "Citizens should be aware they could go through strong shaking and just try to prepare your home. Tie down large bookshelves and computer monitors and televisions and things like that that could fall and fall on you or your children."

"If [shaking] were to occur, say, on the Edmond fault near Oklahoma City, or in a place like Cushing, where the large oil storage facility is, then you'd have considerably more damage," McNamara said.

With more and more action from the Oklahoma Corporation Commission, it does seem to have some affect, though it's not stopping activity completely.

"In very specific cases that we've looked at, like Cushing for example, we have seen a decrease in seismic rate when the OCC limits and shuts down wells in the vicinity, but we haven't looked at it across the state, just a few specific cases."

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