HAYWARD, Calif. _ The San Andreas long has been the fault many Californians feared the most, having unleashed the great 1906 earthquake that led to San Francisco's destruction 112 years ago Wednesday.
But new research shows that a much less well-known fault, running under the heart of the East Bay, poses a greater danger.
A landmark report by the U.S. Geological Survey estimates that at least 800 people could be killed and 18,000 more injured in a hypothetical magnitude 7 earthquake on the Hayward fault centered below Oakland.
Hundreds more could die from fire following an earthquake along the 52-mile fault. More than 400 blazes could ignite, burning the equivalent of 52,000 single-family homes, and a lack of water for firefighters caused by old pipes shattering underground could cause some to emerge into conflagrations, said geophysicist Ken Hudnut, the USGS' science advisor for risk reduction.
"This fault is what we sort of call a tectonic time bomb," USGS earthquake geologist emeritus David Schwartz said. "It's just waiting to go off."
The Hayward fault is so dangerous because it runs through some of the most heavily populated areas in the San Francisco Bay Area, spanning the length of the East Bay from the San Pablo Bay, through Berkeley, Oakland, Hayward, Fremont and into Milpitas. It is one of the most dangerous faults in the nation "because of the density of the population directly on or astride it, which would include San Francisco, and the amount of infrastructure that crosses it," Schwartz said.
As the potential hazards of the fault have become clearer in recent years, officials have begun to take action. Old city halls in Hayward and Fremont that have been abandoned because they lie on the fault. At Memorial Stadium at the University of California, Berkeley, seating was recently broken up and rebuilt so that the stadium's western half could move 6 feet toward northwest from the other side. In the hypothetical earthquake scenario, half of Memorial Stadium would move 2 feet northwest during the main earthquake, and another foot would move more slowly over the next 24 hours, and yet another foot or so over the next few weeks or months, Hudnut said.
But that still leaves much of the region vulnerable, experts said.
The so-called "Haywired" scenario envisions a scale of disaster not seen in modern California history _ 2,500 people needing rescue from collapsed buildings and 22,000 being trapped in elevators, Hudnut said. More than 400,000 people could be displaced from their homes, and some residents of the East Bay may face a loss of water from six weeks to as much as six months.
The report also highlights the weaknesses of California's minimum building codes, which are only designed to keep most structures strong enough to enable people to safely evacuate after an earthquake. Even if all of the 2 million buildings in the greater San Francisco Bay Area complied with the modern-era building code, a Haywired scenario earthquake would cause 8,000 structures to collapse, 100,000 to be red-tagged _ meaning they're too damaged to enter _ and 390,000 yellow-tagged, meaning occupancy is limited due to significant damage, said Keith Porter, a University of Colorado Boulder research professor who coordinated the Haywired report's engineering section.
In some respects, the Haywired scenario would be at least 10 times as bad for the Bay Area as the 1989 magnitude-6.9 Loma Prieta earthquake, despite the similar magnitude. The 1989 earthquake is blamed for about 60 deaths and produced $10 billion in damage; the Haywired scenario envisions $82 billion in property damage, and direct business losses and fire following the earthquake could add $30 billion more.
A Hayward fault earthquake could trigger significant aftershocks on other faults, and could happen as long as half a year after the main shock. In the Haywired scenario, a large late aftershock comes nearly six months later from the main shock _ a magnitude 6.4 earthquake close to Cupertino, the home of Apple's headquarters, and is followed in close succession by a magnitude 6.2 earthquake near Palo Alto, a key city in Silicon Valley, and a 5.4 back in Oakland.
The Hayward fault is one of California's fastest-moving faults, and on average produces a major earthquake about once every 150 to 160 years, give or take 70 or 80 years. The last major earthquake on the Hayward fault, a magnitude 6.8, will see its 150th anniversary on Oct. 21.
"Even given the uncertainties, we are definitely closer to the next one than we are away from it," Schwartz said recently, while showing off the giant crack in the floor of the Fremont Community Center in the city's Central Park that also was built on the Hayward fault, which has slowly grown since it was built in 1962.
Out of the Bay Area's population of 7 million, 2 million people live on top of the fault, Schwartz said. And strong shaking won't only affect the East Bay, but will also be felt in San Francisco and particularly strong in places like the San Ramon and Livermore valleys. "You can't hide _ there's really going to be places in the greater Bay Area that won't be affected," he said.
The location of the Hayward fault is so well known to geologists because in certain parts of the East Bay, it creeps along, moving slowly between earthquakes. That releases some of the seismic strain accumulating on the fault as the Pacific plate slides northwest relative to the North American plate, but not the lion's share.
A major quake on the Hayward fault directly under the East Bay would be much different than other great Bay Area quakes. The 1989 Loma Prieta earthquake was centered in the sparsely populated Santa Cruz mountains, and the shaking felt in the East Bay nearly three decades ago was actually quite mild to what can happen when an earthquake hits right underneath the urban center. The 1906 earthquake was centered off the coast of San Francisco.
Those close the actual fault rupturing in the Haywired scenario can experience such strong shaking that it can cause a grand piano to flip over, said seismologist Lucy Jones. That's why it's a mistake for Californians to think that their home or business is fine if they survived the 1989 Loma Prieta or 1994 Northridge earthquakes, neither of which was directly underneath a densely populated area with many old buildings.
"If you're right on top of the earthquake, it's really a lot worse," Jones said. "What you had in Oakland in Loma Prieta is much less shaking than you're going to get in this one."
The Haywired report has been more than four years in the making, and federal scientists say they hope spelling out the science of what could happen in a plausible earthquake will help inspire people to get prepared.
With decades passing since the 1989 earthquake, "some amount of complacency is to be expected, and it's the same in L.A. after Northridge," Hudnut said. But earthquakes, while rare, can still happen and "can be extraordinarily high impact. So it's not O.K. to forget. We have to remember."
Few people in the Bay Area know exactly where the Hayward fault is located, even in busy neighborhoods like Hayward's downtown.
On a recent weekday morning, two moms who routinely bring their children to a park next to the abandoned Hayward City Hall on Main Street had no idea that the building was closed down because it is slowly being ripped apart by the Hayward fault. There are no markings showing the path of the fault, and kids routinely run up to touch the building, and parents don't know of the risk.
"If it crumbles, that's really scary," said one of the moms, Melanie Koloto, at the park with her 6- and 8-year-old sons. "I think they should already have it blocked off, or try to get it knocked down."
"At least have some kind of public safety meeting _ a town hall or something _ to say this is where it is, and this is the dangers that comes along with sitting right on top of it," said Katie Crystal, 32.
Signs of the fault are evident, according to Schwartz, who recently showed a reporter a tour of the fault. A bent curb and a bent building wall can be seen on the northeast side of Mission Boulevard between A and B streets. In the parking lot behind Favorite Indian Restaurant shows a bump in the asphalt showing the boundary line of the Hayward fault as the western side creeps to the northwest, and the other creeps to the southeast.
Schwartz said the fault continues in a northwesterly direction, which would point it through the property to the northwest _ the St. Regis Retirement Center. The longtime owner, Gene Rapp, 80, said he was unconvinced.
"I don't think a bump in the parking lot ... means anything," Rapp said in a telephone interview. "There's only one way to know for sure. You have to dig a ditch. You can't just look at broken concrete and jump to a conclusion. It might be a wild-ass guess."
