When the quake starts, duck or run?

I learned today that recognized seismic engineering experts are divided as to what people who find themselves inside an older concrete building should do if a big earthquake begins. Whether you decide to duck or to run out, you can cite at least one reputable engineer’s advice in your favor.

How can you maximize your chances if you are indoors when a major earthquake starts? The conventional advice given by most experts to residents of the United States is: Stay inside and crouch under a sturdy piece of furniture.

Residents of Berkeley Town House, a senior housing cooperative, got that advice from a highly qualified seismic engineer, David Ojala, during a March 2017 briefing that I organized. Ojala explained the basis of his opinion as a balance between risks. Residents could be killed or injured trying to flee the building, or, if the building were to collapse, by staying inside, but he estimated the risk from flight as substantially greater.

Until today, I had the impression that this opinion is consensual in the entire fraternity of expert seismic engineers.

Not any more. Now I’m aware that it is at least somewhat controversial when applied to buildings of the Berkeley Town House type, namely older non-ductile (i.e. stiff) concrete buildings. The dissenting opinion that I encountered today is that of H. Kit Miyamoto, set forth in his 27 September dispatch from a tour of earthquake damage in Mexico City. Here is the pertinent passage:

Old concrete structures are one of the most dangerous building types that exist on earth. Their inadequate reinforcing details make the concrete very brittle under seismic motion. All damaged buildings we saw today were this type. You know how we teach people to duck under a desk during an earthquake? We teach this in California. But if I’m in a nonductile concrete structure, I will run as fast as I can outside and so should everybody.

Miyamoto goes on to explain that this advice would not turn out to be right in every situation:

This earthquake was also different from the 1985 one. The Mexico City earthquake in 1985 was a long-distance earthquake with long, swaying motion. This affected taller structures, six stories and higher. But this earthquake had a much sharper and faster shaking motion, which impacted three- to six-story structures more. It’s what we called “resonance effect.” Every earthquake is different and affects different types of buildings. So, one cannot say that a building is safe if it went through one earthquake. Next one can be totally different.

So, unless you know in advance about the characteristics of the next quake, if Miyamoto is right then you can’t be sure whether it is better to duck or to run until it is too late to make the choice. But at least one thing is clear: You can’t do what all the experts recommend, because they don’t.

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