7.1 Mexico quake picked up on Washington seismographs

7.1 Mexico quake picked up by seismometers in Washington's Olympic Peninsula (Photo: Pacific Northwest Seismic Network)

SEATTLE -- A major 7.1 earthquake that struck central Mexico Tuesday was powerful enough to be felt by sensitive seismology equipment in the Pacific Northwest.

"Oh yes, all of them," said Bill Steele, with the Pacific Northwest Seismic Network, based at the University of Washington. "An earthquake of this size is recorded all over the planet."

Steele said the quake that hit Mexico was somewhat similar in the plate tectonics that triggered the 6.8 Nisqually Quake that hit near Olympia on Feb. 28, 2001.

"The difference here is primarily that there are more poorly built structures that are not suited to withstand that kind of shaking produced," Steele said, adding the Mexico quake was also a little bit stronger and wasn't as deep.

But while we have an advantage in the Northwest of modern building codes, some of the older buildings around here are still quite vulnerable to a large earthquake.

"We know that the unreinforced masonry buildings we see in the U-District, in Pioneer Square and Ballard and other parts of the city are extremely dangerous and can collapse during strong shaking," Steele said.

But even some of the buildings built in the past 40 years or so could have issues during quakes.

"What people are less aware of is that the earlier reinforced concrete buildings built in our case before the mid 1970s don't have enough rebar; don't have enough confinement of the cement," Steele said. "So when it begins to crack up from the building rocking back and forth, chunks of cement can fall out and then the building loses its ability to support its weight and it can collapse. And in some cases, the quality of cement can vary greatly."

Steele recommends keeping that in mind when choosing a place to live.

"I can't emphasize that enough," he said. "It seems the market rate for renting an unreinforced masonry building is almost as high as renting a safe building. So to me it's kind of a no brainer: You don't want to put yourself or your kids in danger in poor buildings."

And as always, a large quake can be a call to action to be prepared for whenever the next one strikes the Northwest. Steele noted that those near the Mexico quake center will be dealing with power outages, possible lack of fresh water and other capabilities, so family and personal preparations are really critical.

"Most people survive even these terrible quakes that collapse buildings," Steele said. "But how you survive over the next two weeks depends on how ready you are for that sort of thing. And if you have food and water, you can ride it out and be a support for your family and neighbors; if you don't -- you're part of the problem."

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