Nov. 1 (Bloomberg) -- San Franciscans shaken by the earthquake two days ago are even more unnerved by seismologists' warning that they should be ready for a bigger temblor soon. ``I'm leaving town this Friday, and that makes me happy,'' said resident Michelle Clemensen, who works for a hedge fund. ``I'm not prepared in any way for an earthquake.''
The 5.6-magnitude earthquake that rattled the Bay Area significantly increased the likelihood of another damaging seismic shift in the next few days, a panel of scientists said yesterday. The quake broke windows and tossed items from shelves in San Jose but didn't cause major damage. It was centered near the junction of the Calaveras and Hayward faults, making them more prone to shift soon.
The Hayward fault, which runs under heavily populated Richmond, Oakland and Berkeley, is due. The fault has shifted about every 140 years, seismologists said. Its last big quake, 139 years ago, was estimated at magnitude 7, leveled buildings and killed 30 people.
``We're pretty sure it's ready: It could be tomorrow or it could be in 10 years,'' said Roland Burgmann, geophysics professor at the University of California, Berkeley. ``The Hayward fault is considered to be the biggest risk in the area.''
Even seasoned earthquake survivors were startled by the bluntness of the warning from the California Earthquake Prediction Evaluation Council, a panel of scientists that advises Governor Arnold Schwarzenegger's Office of Emergency Services.
``This is very scary,'' said Marylou Luckhurst, a suburban resident who works in the city and had a close call in the 1989 Loma Prieta quake. ``I hope I can get home. I have two dogs, and they would be terrified.''
Apocalypse Box
Some people in the Bay Area are prepared for a disaster in their high-risk zone. Seamus Giffen, who works in San Francisco's financial district and lives in the northern suburb of San Rafael, has an earthquake- preparedness kit he calls his apocalypse box. It holds canned food, water, flashlights, a radio and extra clothes.
``It was Katrina that gave me the idea of a disaster where somebody wouldn't be able to bail me out,'' Giffen said. ``It made me want to be a little more self-reliant.''
The next event could be worse than the 6.9 Loma Prieta, 75 miles (120 kilometers) south of San Francisco, which killed dozens of people and severely damaged structures around the Bay Area, scientists said.
``You would have buildings literally torn in half, roads and freeways that would be offset, railways that cross the fault would likely be damaged and impassable,'' said Steve Walter, a seismologist for the U.S. Geological Survey.
Relatively Low Risk
While this week's event makes a major earthquake more likely, the probability nonetheless is low, the panel of scientists said in its statement.
It called the probability above normal along the Hayward, the Calaveras or both. Before this warning, the U.S. Geological Survey estimated the probability of an earthquake on the Hayward fault at 27 percent by 2032. It hasn't updated the long-term forecast.
``It's a significant increase statistically in the scientific world, but it is still a very low probability,'' said John Parish of the California Geological Survey. ``It's as if you know one number in the state lottery. You still have to guess the next seven.''
On Oct. 21, 1868, the Hayward fault shifted about 6 feet (2 meters). The resulting earthquake caused five deaths in rapidly growing San Francisco, which then had a population of 150,000, and caused as much as $100 million of damage in today's dollars.
Danger of Landfill
One lesson scientists learned in 1868 was that the damage tends to be most severe to buildings constructed on ``made ground.'' Even more of the Bay Area rests on landfill today, including the Oakland International Airport.
A magnitude 6.9 earthquake along the Hayward fault could leave 155,000 homes uninhabitable, 360,000 people homeless and more than 110,000 people in need of public shelter, according to the Association of Bay Area Governments. Magnitude indicates how much energy an earthquake releases, based on the physical area of the moving fault.
Power outages would be widespread, more than 1,600 roads would be closed, and phone systems would be overwhelmed, the group said.
More than 600,000 employees earning $8.2 billion in quarterly payrolls work along the Hayward fault, the U.S. Bureau of Labor Statistics said in a September report.
Some residents aren't any more worried about earthquakes than they were before the warning.
``It's really no big deal,'' said Larry Nelson, 55, a banking executive who has lived in the area for 30 years. ``It's what we expect when we choose to live here.''