Oklahoma's seismic activity may not be over, experts say

By Matt Dinger and Tiffany Gibson Published: November 7, 2011
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The 5.6 magnitude earthquake that shook the state Saturday night did not cause significant damage nor have any serious injuries been reported — but the seismic activity may be far from over, scientists said.

The brunt of damage has been reported in Lincoln County, the epicenters of recent quakes, and in adjacent Pottawatomie County.

Minor damage to 12 homes was reported, and a stretch of U.S. 62 buckled in Lincoln County, said authorities. One building on the campus of St. Gregory's University in Shawnee also was damaged.

After the main shock, there were 12 temblors registering at magnitudes of 3.0 or higher and more than 70 quakes with magnitudes of 1.0 to 2.5, Oklahoma Geological Survey research scientist Amie Gibson said Sunday.

Those quakes — often known as aftershocks — are defined after the fact. A 4.7 magnitude earthquake that hit at 2:12 a.m. Saturday was initially thought to be the main shock until the 5.6 magnitude quake struck later in the day. That defined the earlier event as a foreshock, Gibson said.

“They're all individual earthquakes. People like to lump them in. It kind of helps people understand the sequence of events,” she said.

While scientists cannot predict earthquakes, Gibson said she would be surprised if they suddenly stopped considering the high amount of seismic activity over the weekend.

“With the pattern we're looking at, I don't see it stopping anytime immediately soon. I'd like it to stop, but I don't see that happening right now,” she said.

“We really hope that the 5.6 was the main shock because I don't want to see anything like that again, personally. It would be ignorant to assume anything right now, because who would assume that we'd have the two biggest ones in one day?” Gibson said.

Record-breaker

Before Saturday night, the strongest earthquake recorded was April 9, 1952, in El Reno, according to the geological survey. Its magnitude was 5.5.

U.S. Geological Survey geophysicist Don Blakeman said the agency doesn't know why Saturday's quakes struck so close together.

He said Oklahoma sits in the middle of the North American plate, which sometimes can build up pressure that would trigger an earthquake.

Oklahoma Natural Gas spokesman Don Sherry said that no ruptured gas pipelines have been reported.

“Pipelines are designed to withstand a lot of that stress. It doesn't appear that we've had any significant operation difficulties,” Sherry said.

Gas pipelines are monitored remotely 24 hours a day from the Oklahoma City office, he said.

ONG supplies about three-quarters of the state with natural gas, including Lincoln County.

“If we did experience some sort of damage associated with pipelines, we'd know about it pretty quickly. Just because they're buried beneath the ground doesn't mean we don't know what's going on,” Sherry said.

Engineers consider seismic activity when the pipelines are designed and installed, and pipelines routinely undergo inspection, Sherry said.

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Did you know?

WHAT to do

• Check for injuries and provide necessary first aid

• Check for gas, water, downed power lines and shortages, then turn off utilities if necessary. If you shut off the main gas valve, wait for the gas company to check leaks and make repairs and do not turn it back on yourself.

• Turn on the radio for safety instructions and recovery actions.

• Only use the telephone for emergencies.

• Follow your family emergency plan, be cautious when opening cabinets and stay away from damaged areas.

• Be prepared for aftershocks.

Source: Oklahoma Department of Emergency Management

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