Saturday, April 01, 2006
Coming soon, an anniversary
On April 18, you are likely to be seeing a multimedia showcase in every news source available about the 1906 San Francisco Earthquake. It was a magnitude 7.7 to 8.3 (disagreement abounds on this one, due to it occurring before the science of seismology was as advanced as it is now, and the magnitude being determined by historical accounts, rather than seismograph readings). It affected some 300 miles of the San Andreas fault, resulted in 700 recorded deaths (though the USGS says that there were probably 3 times as many deaths), and caused the great San Francisco Fire. By comparison, the Loma Prieta Earthquake of 1989, which caused such damage to the SF Bay area, was a 7.0 magnitude. Thus, the 1906 earthquake was anywhere from 7 times as intense to 13 times as intense. Think of that. Anyone who was in SF during and after the Loma Prieta quake, and recalls the great damage that was done by that, should stop and think just how devastating an earthquake of the magnitude of the 1906 quake would be. The USGS has a fantastic website about the 1906 quake. But even more interesting, in a horrific and amazing and intriguing way, are the simulations of the ground movement on another USGS website, passed on to me by OmegaGranny via email this morning. The main simulation at the top shows waves of movement rippling outwards from the San Andreas Fault, a great overview, but it's the regional and local views that are staggering. The simulations exaggerate the ground movement by 1000 times, so that it's easy to see over large areas, and the effects are awe-inspiring. You can watch the ground move horizontally and vertically, as each ripple sweeps past. Even the low-resolution clips are big (5 MB, for example), so don't click on them unless you have a good broadband connection. When I moved to the Bay Area in 1990, many friends and relatives all gasped: "Aren't you afraid of earthquakes??" they asked. Well, a little bit, but you don't really grasp what it's like until you've been through one, I'd surmise, and besides, it had been 73 years between biggies so I figured I was safe for quite a while. There were ongoing aftershocks still hitting after I moved there, and it made for interesting moments when I was out hiking and a small earthquake would hit--one moment I'd be striding along, the next, the ground wasn't quite where my body was expecting it; it leaves you feeling somewhat surreal and staggering to find the proper rhythm again for a few seconds. OmegaGranny spent much of her youth in California, and she recalls her grandmother rushing to stand in front of the highboy, arms outstretched to keep her precious china in place, during earthquakes. This is, of course, not the proper thing to do during a big earthquake, but it illustrates the mindset that human beings get into when confronted with ongoing natural phenomena that become just part of doing business and getting on with life. I became quite blasé about little 5.5-ers in much the same way that folks who live in hurricane country become blasé about hurricanes (pre-Katrina)--it's just something you live with and deal with, most of the time. Earthquakes come out of the blue, there's no way (currently) to predict them, so you get on with life and don't let the worry preoccupy your mind. Living in California, I soon learned to be much more concerned with fires, floods and mudslides; these are natural phenomena that occur with much more frequent regularity. September, October, November--those are fire months. January, February, March--those are flood and mudslide months. Having missed the Loma Prieta earthquake, I was there for the Great Oakland Firestorm; it's very sobering to come to work realizing that everyone you know knows someone whose safe, cozy home was wiped out in 20 minutes... No matter where you live, even in these highly technological times, Nature trumps all. Where the Omegas live now, in the midst of a nice, toasty-dry Ponderosa pine forest, the stupidity of a Valley camper leaving a campfire unattended or the strike of a bolt of lightning in a dry tree could ignite a fire that would leave us homeless. But we still live here...just as folks in Tornado Alley still live there...just as folks in earthquake country continue living there. You make the preparations you can, and live your day-to-day life, and don't let the knowledge that out of the blue, Nature can make it all come crashing down, overbear you. Keep on keeping on, and keep an eye out for more articles about the 1906 earthquake.