SPENCER MICHELS, NewsHour Correspondent: San Francisco, April 18, 1906. One hundred years ago, a devastating earthquake shook the city like nothing before or since, and set it on fire. Today, San Francisco is ablaze with remembrances of the catastrophe and warnings of future quakes.
At least three major art museums have earthquake shows featuring photos of the devastation, some taken by writer Jack London. Tourists walk through downtown on an earthquake tour.
TOUR GUIDE: That was the call building that I showed you a picture of that burned.
SPENCER MICHELS: Many San Franciscans look upon the legacy of the 1906 earthquake and recovery with pride, rather than with fear. Here in Golden Gate Park, they are celebrating the '06 quake with an intricate floral display.
This is the park where thousands of San Franciscans, including my own grandparents, came after the earthquake to live temporarily in tents, while their own homes were damaged or burned.
As director of emergency services, Annemarie Conroy knows how deadly the '06 quake was: her own great, great grandmother died, along with an estimated 3,000 people, 490 city blocks were destroyed. A quarter of a million people were made homeless.
Conroy is concerned that San Franciscans don't take earthquakes --past and future -- seriously enough.
ANNEMARIE CONROY, Director of emergency services: I think we do find a sense of complacency, that we think about '06 and the city survived and it went on and what a beauty she is now. That was a horrible, devastating event. Thousands of people were killed, 225,000 were left homeless. Half the city was gone. We don't really look at it from that perspective and people need to remember that was a horrible, horrible, catastrophic event and that could happen again to San Francisco.
SPENCER MICHELS: With seven major fault zones throughout the bay area, scientists say there's a 62 percent chance of a major damaging earthquake in the next 25 years.
If the quake were a repeat of 1906, 7.7 with the epicenter just offshore -- there would be almost no time to escape, says seismologist Mary Lou Zoback of the U.S. Geological Survey.
MARY LOU ZOBACK, Seismologist: Within two or two and a half seconds, San Francisco would be enveloped by strong shaking. Within seven seconds, the strong shaking would hit Berkeley and in 20 seconds, it would hit San Jose. So within 20 seconds, the entire bay area would be shaking violently.
SPENCER MICHELS: Zoback estimates the number of deaths in the thousands.
MARY LOU ZOBACK: Most people in the urban parts of the bay area live in homes built prior to modern building codes.
SPENCER MICHELS: And they could collapse.
MARY LOU ZOBACK: They could collapse, particularly the homes that are built over open garages. And many deaths will occur in those homes.
SPENCER MICHELS: This simulation --based on scientific data, shows that the ground shook for 300 miles along the San Andreas Fault, and would again in a similar quake, creating havoc far from the epicenter.
Engineer Chris Poland chairs an earthquake conference, which commissioned the video.
CHRIS POLAND, Engineer: It shows that we expect strong ground shaking, stronger than we really experienced in any of our memories. It shows us that buildings are going to be damaged more than we would have expected, especially the older buildings. The newer buildings will not be usable for a few weeks, a few months, even a few years while they're being repaired. And that's of great concern to us.
SPENCER MICHELS: Poland says today's advanced building techniques can cut down damage, but may be very expensive, especially for old buildings. What's key, he says, is preserving the area's economic vitality, by deciding what buildings must be seismically upgraded, and how to fund such work.
CHRIS POLAND: I think we have a long ways to go to recognize which buildings we need, which pieces of infrastructure we need. And those are the ones that need to be strengthened so that we don't get caught in a situation like they have in New Orleans right now, where the economy just won't start. The city has no money because there's no base, there's no economic, there's no business running, there's nothing going on.
SPENCER MICHELS: Key portions of the bay area's infrastructure are threatened. Engineers and scientists agree that structures built on filled-in land, near San Francisco Bay are the most vulnerable to damage, just as they were in 1989, when a quake much smaller than '06, and centered 60 miles away, collapsed homes and started fires in neighborhoods.
MARY LOU ZOBACK: Those areas, when subjected to strong shaking, often the ground liquefies and then it can just drop away.
SPENCER MICHELS: Whatever is built on such soil is at high risk, including freeways and the San Francisco Airport. The bay bridge, part of which collapsed in '89, is still being reconstructed. And the Bay Area Rapid Transit system needs to reinforce elevated tracks, and attempt to beef up tunnels, some of which traverse earthquake faults.
But upgrading buildings, or replacing them, takes time and money. Chris Poland's engineering firm is working on a new hospital, and is studying schematics showing how various designs would behave in an earthquake.
City-run Laguna Honda Hospital for low income, long-term care is being entirely rebuilt, in accordance with a state law mandating that all hospitals be safe in earthquakes.
The huge TV broadcasting tower, which could collapse with devastating results, is being strengthened. The city is rebuilding reservoirs. And City Hall, which had been destroyed in 1906, was closed for three years, following the '89 quake. The building was retrofitted with devices that isolate the base from the ground, and structural supports.
SPENCER MICHELS: It is a myth to say San Francisco -- even in 1906 -- had been complacent about earthquakes, says Stephen Tobriner, an architectural historian at the University of California. He pointed to several buildings that survived the '06 quake and still exist today. The old Call newspaper building caught fire after the earthquake, but it remained standing, and is in use as an office building.
In its basement are 100-year-old structural steel braces that flex when the ground shakes.
STEPHEN TOBRINER, Architectural historian: They're supposed to dissipate energy as they move back and forth. They can't be too stiff or they can shake themselves to pieces because of that stiffness.
SPENCER MICHELS: Despite such innovative construction, buildings collapsed and fire raged. In fact, 90 percent of the deaths in '06 were caused by uncontrolled fire. Fearing a repeat of such a holocaust, 11,000 residents have volunteered for training to help the likely-overwhelmed fire department, like some residents did spontaneously in the '89 quake.
LUDWIG HERRMANN: We've come to realize that we can't depend on the federal government to protect us anymore, especially in light of the Katrina disasters. So this is - that's been a real motivation for us to do hands on, and do the best we can to take of ourselves, our neighbors and our community.
SPENCER MICHELS: Firefighters and police have also gotten extra training, thanks to money given for homeland security. Exercises like this mock bioterrorism attack are becoming frequent throughout the area.
But the fire department will need water. In 1906 the underground pipes broke. As a result, San Francisco pioneered an auxiliary water supply system, the only one in the nation that provides high pressure water separate from the drinking water supply for use against fires.
Assistant deputy chief Lorrie Kalos says the city also installed these pumps to suck salt water from the bay, in case freshwater mains break or there isn't enough fresh water.
LORRIE KALOS, Assistant deputy chief: We also have fire boats and we have portable hydrant systems that we can put into place so that we can bring water to where we need it.
SPENCER MICHELS: Kalos says the department -- with 340 people on duty every day -- has improved its communications, provided adapters for its hydrants so other departments can use them, and has planned for a major disaster.
LORRIE KALOS: When we get to that 10-point earthquake and the streets sever and there's a separation of four feet, do we think water mains are going to hold in their place? No. Do we have auxiliary plans? Absolutely.
SPENCER MICHELS: But, as many experts have said, older, single family homes built over garages may be the worst problem in a big quake, leaving thousands homeless, perhaps unnecessarily so.
HOWARD COOK, Contractor: It's an absolutely horrible problem. I see Hurricane Katrina repeating itself here in the San Francisco Bay Area. I see houses that I can look at from the outside and I can say, "This house is going to fall down." I know that.
SPENCER MICHELS: Howard Cook, a contractor specializing in retrofits, has inspected hundreds of bay area homes. Homeowner Jay Tibits (ph) asked Cook to check out his house, on Twin Peaks.
HOWARD COOK: This is the edge of your floor, right here, of your house. And if you look, there's nothing really supporting it for back and forth motions like this except air.
SPENCER MICHELS: Cook says California's building codes for homes barely address retrofitting, and that many contractors don't have the training he does to protect homes.
HOWARD COOK: When the floor starts to rock back and forth like that, we're going to hold it right here. And if we hold it right here, the whole front's not going to move.
HOWARD COOK: So you're really lucky. Most houses in San Francisco are not like this.
UNIDENTIFIED MALE: OK.
SPENCER MICHELS: Still, Cook says, it will cost Tibits (pH) about $10,000 to retrofit his home. Some San Franciscans scoff at all the concern, saying their city hasn't had a direct hit in a century. But emergency officials and engineers are hoping that the focus on the '06 anniversary, plus Katrina, will wake up the city.