April 18, 2006 9:50 PM PDT
Tracing the shadows of the Big One
In search of traces of the Big One, an international group of earthquake fanatics explored the streets, facades, basements and rooftops of downtown San Francisco.
A century after the catastrophe, its traces can still be seen. In the financial district, the few old survivors of the earthquake and fire--buildings with ornamented facades and a distinguished patina--stand cheek to cheek with light-reflecting skyscrapers that took the places of the survivors' less fortunate neighbors.
It was no coincidence that some houses survived while others collapsed, according to our guide, who wore a black suit and cowboy hat. Steven Tobriner, an architecture professor from University of California at Berkeley, knows every nut and bolt of the buildings that still exist and those that fell.
"I am a fourth-generation San Franciscan," he said. "I was brought up in one of the first houses that were rebuilt. My father and grandfather both lived through the earthquake."
But you don't have to be a San Franciscan to have a relationship to earthquakes. One man in the group came from New Zealand and works for a government organization trying to prepare that country's citizens for movements in the island's unstable fundament.
Kiwis are advised to keep an emergency kit in the house, place a sticky mat under the expensive TV and place heavy objects on low shelves. And don't forget to buy a garden table with raised edges, so the barbecued steak doesn't fall off when an earthquake interrupts the garden party.
Even those who have never felt a decent-size earthquake know someone who did, or someone who knows someone who did, or at least they have heard the myths.
Several of the tour participants work for building-insurance companies in London, where the seismic movements are too small for humans to feel. "I heard there was one in Birmingham once that made people fall out of their beds," one girl said.
On a corner at the intersection of Market and Third streets stands the Central Tower, a seismic retrofitter's dream. As you look at the tower's pinkish sandstone facade, its strengths are not apparent. But as the group descends into the building's basement, zigzagging between dusty ladders and forgotten cleaning apparel, the tower's steel skeleton comes into view.
The tower wears braces like a sprawl-toothed teenager, allowing it to sway but not collapse. It was built in 1898 and stood steady in the quake, although the top floors burned.
"An architectonic masterpiece," said Tobriner with a delighted smile on his face, pointing to the building's firm foundation and independent water pump backup system.
Next stop is a scavenger hunt at Jessie Street, a small alley between pre-1906 buildings. "Can you find the damages after the earthquake? There are at least six. I'll give you three minutes," the excursion leader commands.
When every crack and missing splinter have been found, scrutinized and explained, the expedition and discussions can continue. Should buildings be strong and stiff, or light and flexible? Rely on steel or wooden frames? Concrete or brick, tiles or plaster?
Three hours later, our necks are sore from gazing up at high-rise facades, our feet weary and our ears tired from listening. But everyone on the tour knows how to construct an earthquake-proof building.