San Francisco shook twice yesterday, and it wasn’t from a Giants game.
Almost 22 years to the day after the Loma Prieta earthquake rattled the Bay Area during the 1989 World Series, two quakes occurred yesterday along the Hayward Fault, with epicenters several miles below the UC Berkeley campus. At 2:41p, I felt the first one (4.0) from our lab in the SoMa district of San Francisco – a rumble that jiggled parked cars on the street. At 8:16p, I felt the second one (3.8) from our much closer second story apartment in Oakland and did a mental double-take as I truly felt the house shake for a moment. Of course, Facebook and Twitter had a flurry of status updates as people all across the Bay Area shared their experiences.
When my wife and I moved here from Boston three years ago, we traded snow for earthquakes. I personally don’t mind these relatively small earthquakes, in that by relieving fault pressure they delay “The Big One“. Even when that one hits, I have some faith that it may not be as bad as what I saw in Haiti last year.
Here you can see a bit of earthquake physics you might not have realized – that on multi-story buildings, it is actually safer to be higher up. Notice that the first floor has been completely crushed and the third floor is comparatively unscathed. My faith that California will weather a large earthquake better is due primarily to the three following things that Haiti does not have;
- Higher quality building materials – What I saw in Haiti was cement that crumbled to the touch and woefully thin rebar
- Better building techniques – California in particular practices seismic design principles
- Adherence to building codes – Perhaps most important, for without this the other two become meaningless
This is not to say that Californians should be complacent, but our awareness and continued engineering advances should give us a decent chance of avoiding the devastation that I saw in Haiti.
(Related pictures of Haiti 2010 can be found here.)