Sunday, February 28, 2010

Earthquake Preparation

Tale of Two Quakes: Chile Was Ready, Haiti Wasn't - International News | News of the World | Middle East News | Europe News -

There is a difference between governments being prepared and people being prepared. I used to live in California where there are many earthquakes. We were constantly harangued on the TV, on radio and print that we should be prepared for "The Big One". Which one? The 8.0 or bigger earthquake that is going to wipe out everything. As horrifying as that prospect is, most Californians are at least mentally prepared and somewhat physically prepared.

Chilean Leadership told their people that for three days everyone was on their own. Emergency crews would be concentrating on rescues. Anyone who was moderately OK was not going to get much in terms of help. That squares with what I recall in California during the Sylmar Earthquake. I was just a boy but I remember my father being gone (and out of communication with us) for three days. He was a telephone lineman with a priority job in reestablishing phone lines.

From a mental point of view, since small earthquakes are common in California we were given gentle reminders to prepare. Chili was the same way but not Haiti. The last major earthquake in Haiti was over 200 years ago. Their building codes were not in line with surviving a major earthquake. Many buildings are not.

I remember watching a "This Old House" episode where the guys were sprucing up an old colonial house. As they gutted the interior walls they exposed the framing and pointed out a number flaws in old building practices. What they failed to point out was that there was no cross-bracing. Then to my horror they began cutting out a space in the wall for a picture window TOO CLOSE TO THE CORNER of the building. From an earthquake point of view that picture window weakened the corner of the building and when it swayed in an earthquake, that corner was going to tip over because it had very little lateral support. I assume the house was not in an earthquake-prone area because a proper building inspector would insist on cross bracing and the window further away from the corner.

Local building codes incorporate lessons learned from the last time something terrible happened. Thus, Chilean building codes no doubt incorporated any number of requirements for a building to survive an earthquake. Deeper foundation footings means they won't pull out of the ground while the building sways back and forth. Proper cross-bracing means your walls won't fold up like a house of cards. If you are inside, it is deadly. The only thing worse may be going outside.

Remember that no matter how bad it gets inside, it is probably deadly outside. Building facades peel off if they are not secured properly to the walls (building codes!). As you run outside you can get hit with a brick in the head. Remember that if your home is built properly, the whole building facade could be thrown into the street and the rest of the structure should still be standing.

The other mistake people make with buildings is cranking down on the j-bolts that hold the sill plate in place. Your home is attached to the foundation with a series of bolts embedded into the concrete and then a sill plate (a long board that the wall is build upon) has holes drilled into it where these bolts stick out. A washer and nut are used to keep the sill plate locked down and basically keeps the walls from slipping off of the foundation. However, if you tighten those bolts too much, the walls cannot slide around during an earthquake. Without that "give" the energy from an earthquake is transferred from the foundation into the walls and the walls will crack. This may make the difference between cosmetic damage that can fixed with a little plaster and paint or structural damage which will render your home uninhabitable. Don't crank on those bolts. The building codes will advise how tight to make them.

That is off the top of my head. I may have other thoughts later on.

I used to be a soils technician in Southern California representing the civil engineer in the field. I am not an engineer and if anyone thought I was giving them specific advice... I was. I told you to follow your local building codes. Don't blow them off. They are as an important preparation as anything. You will have a difficult time surviving a disaster if your house collapses. Make sure it will hold together.

Alex Shrugged.