The Enid News and Eagle, Enid, OK

December 7, 2013

Can quakes hurt tornado shelters?

By Dale Denwalt, Staff Writer
Enid News and Eagle

ENID, Okla. — With the recent onset of more noticeable earthquakes in Oklahoma, one part of the state’s disaster preparedness may be faltering — literally.

Earthquakes above a certain magnitude are known to cause damage. Even smaller quakes can separate bricks and mortar, and even concrete slab foundations.

And with many tornado shelters built from concrete, those same types of cracks might cause structural instability. There also may be effects on more rigid structures if they are pulled from their moorings.

Storm shelter design codes warn against deterioration, but there are few instances of researchers discussing the effect of earthquakes on them.

The consensus among scientists is that damage is more likely to occur when an earthquake registers stronger than a magnitude 4 or 5. According to data from the Oklahoma Geological Survey, these have been rare, although there was a magnitude 4.8 temblor near Edmond Saturday.

Enid/Garfield County Emergency Management Certified Director Mike Honigsberg said it’s a good idea for a person to check out their shelter after an earthquake. Every time he visits his shelter, he looks at it to make sure there are no signs of structural instability.

“If I feel a good rumbling, I would have it inspected,” he said. “Common sense tells me if I have a structure and I feel a really good rumble through there, I want to get it looked at.”

His own shelter is below ground, in his garage. It’s rated to hold the weight of his pickup as it’s parked above it.

“If there was cracks running through there, I would probably re-think that protocol,” Honigsberg said.

In his day job, Honigsberg plans and prepares for major disasters. Earthquakes are an obvious one of those possible hazards, but he concedes there’s not much to be done in advance of a damaging quake.

“There’s not much we can really do to prepare for it other than it may cost you to add earthquake insurance. To me, that’s money well spent,” he said.

There are theories as to why there has been an uptick in earthquakes that are felt by Oklahomans, including one that suggests injection drilling following hydraulic fracturing could be a cause. Honigsberg dismisses that idea.

“What people don’t realize is we have several fault lines going through Oklahoma. We always have. They just haven’t been really super active,” he said. “Something is causing them to become active.”