Wednesday, August 24, 2011

When the earth moved

This image from the US Geological Survey shows you the most recent earthquakes in the "lower 48" of the USA. I know that some of you find us Californians unsympathetic, especially to those of you more distant from the epicenter, but if you look at how often the earth moves here, you'll realize why. I lived away from CA for many years and shortly after I came back, I remember being awakened one night by a shaker. My internal Richter scale calibrated it as around a 3.5 or 4 so I rolled over and went back to sleep.
There are a couple of big differences that make this experience very different for the East than the West. We build for quakes out here; I remember when I moved to the east coast I was discomfited that the labs didn't have "earthquake strips" across the shelves--these are wires strung across to keep the bottles from leaping off in a temblor. Brick isn't used here as a major building material in CA. Public buildings are built with quakes in mind, and not to survive long term, but to protect the inhabitants. Retrofitting is continuous, with big steel cross beams obvious on older structures. Cautious Californians strap their water heaters to the wall, use earthquake-resistant cupboard latches, keep water and emergency gear nearby and the camping gear accessible. We have regular earthquake drills. The east coast is simply not prepared for the once-in-100 years event; for one of us, a 5.9 is once every couple of years. (On the other hand, you know how to deal with hurricanes, which probably would freak out most left-coasters.)

The geology is different too. The younger crust in the west dampens the shake sooner, so (for example) the 7.2 Mexicali earthquake in 2010, more than 10x the magnitude of yesterday's Virginia quake, was dampened to a long, long roll in San Diego, just 100 miles away. Very noticeable, enough to roll some things off tables, but not with the sharp jerks and pitches of a nearby earthquake. Mexicali was badly damaged, but it was localized. On the other hand, a 7.0 earthquake in Haiti caused national devastation there.

Now, let's go to the doorway thing. Turns out that standing in a doorway is NOT the preferred spot. Experts recommend getting under something sturdy, like a table. On earthquake practice days, I've been known to insist that 15 people in a meeting with me crawl under the table to continue the conference when the "event" occurs. The biggest danger (particularly in houses) is stuff coming off shelves and breaking on you, not the house coming down. Keep shoes around so you aren't walking in broken glass. But running outside is much worse, because of collapsing glass and masonry. So stay inside till the shaking stops! Be prepared to survive 2-3 days with no help, and known how to turn off the water and the gas. Remember, the worst destruction in 1906 San Francisco was due to fire. (Oh yes, both my grandmothers went through that one.)

I am very glad, given the different geology, and different building codes, that everyone came through safely. I'm sad about the National Cathedral and other damaged buildings, but buildings aren't important: people are. I' m amused that the epicenter was in uber-Republican Eric Cantor's district. Remember he wants to cut funding for the USGS, along with other scientific research. Now, has anyone blamed it on the gays yet?


it's margaret said...

It was ummm amusing to say the least to witness the reactions to the quake. People were running outside in a panic!!!

And, it did indeed feel different here --honestly --I was out in the street and it was not the shaking that got my attention (I don't feel 'em until they are over 5.0 anyway!) -I thought it was a huge truck or perhaps an airplane overhead that was going to crash --the NOISE was incredible. The only other time I have heard such a racket was an earthquake in the desert that caused friction in the sand and made noise.

But our old over-built homes in this neighborhood all fared well --very glad I was in the street already and not in one of the downtown buildings!

Brother David said...

Yes, it really seems strange when folks no where near a tectonic convergence zone experience a quake. The faults are likely remnants of the breakup of the most recent supercontinent, Pangea, 260 million years in the past, as she rears her head to ask that she not be totally forgotten!

Brother David said...

And in answer to your final question dear IT, yes. But not having a male member to shake, (unless you have bought one somewhere!) I am not sure how this really applies to you women.

Rabbi Yehuda Levin Blames Washington, DC Earthquake On Gay Marriage

Counterlight said...

Since 1996, New York has earthquake specific building codes as strict as San Francisco's. There remain a lot of older buildings, especially tenements, that need to be retrofitted.

California is not alone in experiencing regular seismic activity. The Mississippi Valley still shakes from the New Madrid fault. I experienced window-rattling tremors in St. Louis twice in 3 years.

The earthquake precautions sound a lot like tornado precautions. The biggest hazard is from flying debris. The safest place is under something heavy away from windows.