From the Newsroom: Feeling a Little Shaky after the ‘Ultimate Seismic Jolt’

Ever sit back and watch an earthquake? Not a bad spectator sport, although you may come away feeling a little shaky yourself.

On June 21, I joined a group of earthquake experts, contractors, students and journalists at University of California San Diego’s “shake table” to watch an event touted as the “Ultimate Seismic Jolt”: a two-story wood-frame house being demolished by a simulated 6.7 magnitude quake (the same as that which caused $12.5 million worth of damage in Northridge in 1994).

The surprise was, the house itself wasn’t demolished. It was the non-reinforced furnishings that caused the most damage during that intense 20-second period. Flower pots came careening down from window ledges, bookshelves dropped off the walls, a file cabinet spewed its contents across the floor, chandeliers danced crazily.

The test was part of the California Universities for Earthquake Engineering (CUREe)-Caltech Woodframe Project, funded mainly by FEMA, and was intended to test the performance of woodframe housing during an earthquake. Ninety-nine percent of Californians live in woodframe homes, yet little research has been done on how to improve their safety.

“The structure is built according to current building codes—this validates whether these codes are adequate,” said the project’s principal investigator, Professor Andre Filiatrault, speaking to the crowd minutes before the shake. “We want to quantify what the influence of stucco is on the overall performance. Inside, we have well-anchored items versus non-anchored items. There are two of everything: entertainment centers, water heaters, bookshelves, filing cabinets.”

The house was also wired with 300 sensors connected to walls and cross-beams, inside and out, to provide data for researchers.

“This is the ground motion that was recorded in the Northridge quake in 1994—we are exactly reproducing that,” Filiatrault said. “This is a very severe, very intense ground motion, 6.7 Richter magnitude. You will feel a pulse—if you were standing on the first floor, you would experience a force equivalent to roughly 100 percent your body weight. If you were on the roof, it would be double that.”

After much build-up of suspense, I held my breath along with the waiting crowd for one minute of complete silence. Then the shaking started.

Twenty seconds later it was quiet again, and the house was still standing. The windows did not blow out, no tiles came crashing down off the roof, no walls buckled or ceilings collapsed.

“I expected a lot more damage,” said one member of the Valentine Construction team who built the house. “I don’t think they got much out of it, although the flower pots were a nice effect.”

What did happen was a sizeable shift in the house’s contents in a way that could be extremely dangerous to its inhabitants.

“In terms of structural components, the house performed very well,” Filiatrault said. “The problem was the contents—it was an example of what to do, what not to do. Obviously, what you should do is secure your contents. On the unsecured items, such as the water heater, it threatened to break off the wall.”

The verdict? “[The test] was a success from the standpoint that the structure appears to have been strong,” said Jill Andrews, manager of education and outreach for the project. “We did a test on June 30 that was the same thing except there was no stuff—no contents or stucco. This time the house itself performed well because of the stucco—there was four times more damage in the previous test.”

Andrews pointed out that the test didn’t quite resemble a real quake in that “this was just a single degree of movement, also there was no aftershock activity. In a real quake, there would be prolonged shaking.”

The real deal is a harrowing experience, one elderly bystander recounted. “That 15 seconds feels a lot longer when you’re in it… it’s horizontal and vertical all at once. I was in the 1937 Long Beach earthquake, let me tell you, it was 10 times worse than that. It dropped every school building around. Really scary—I never want to live through that again.”

The California Earthquake Authority (CEA) is funding part of the project in an effort to develop new standardized guidelines for adjusting insurance claims post-quake. Spokesman Mark Leonard said the CEA-funded portion of the study will ask insurance-specific questions. “Some questions concern the stucco: ‘how do you repair it?,’ ‘when repaired, will it hold?’ Also the claims adjusting guidelines: ‘when do you bring in the claims adjusters?’ We want to establish guidelines to simplify the process and to avoid disagreements.”

Perhaps most importantly, watching the house’s furnishings fly around like a scene out of Poltergeist, the seismic test illustrated the importance of adequate contents coverage.

“The contents themselves are an incredible safety hazard,” Leonard emphasized. “Insurers should be more proactive in telling policyholders how to retrofit their homes. There are things such as big velcro patches to put the TV on that are so easy but can make a big difference.”

I tried to picture myself in such a situation, probably crouching in a doorway as I had been taught way back in grade school. Is that still the best place to go in an earthquake? Nope, Leonard said. “Your best bet is to get under a heavy table or similar shelter. If you’re in a doorway, that door can blow shut and smack you with a 1-G force.”

Hmm, I think I’d rather sit back and watch the action on a shake table.