New cracks appear in Elke DeMuynck's ceiling every few weeks, zigzagging across her living room, creeping toward the fireplace, veering down the wall. Month after month, year after year, she patches, paints and waits.

"It definitely lets you know your house is constantly shifting," DeMuynck said.

So do the gate outside that swings uselessly 2½ inches from its latch, the strange bulges in the street and the geology students who make pilgrimages to her cul-de-sac.

DeMuynck could throw her paint brush from her front stoop and hit the Hayward Fault, which geologists consider the most dangerous in the San Francisco Bay Area, if not the nation. Like others who live here, she gets by on a blend of denial, hope and humor.

It's the geologists, emergency planners and historians who seem to do most of the worrying, even in this year of heightened earthquake awareness for the 100th anniversary of San Francisco's Great Quake of April 18, 1906.

Several faults lurk beneath this region, including the San Andreas Fault on the west side of the Bay area, but geologists say the parallel Hayward on the Bay's east side is the most likely to snap next.

"It is locked and loaded and ready to fire at any time," said U.S. Geological Survey seismologist Tom Brocher.

The Hayward Fault runs through one of the country's most densely populated areas; experts say 2 million people live close enough to be strongly shaken by a big quake.

It slices the earth's crust along a 50-mile swath of suburbia east of San Francisco, from exclusive hilltop manors overlooking the bay to Hayward's humble flatlands. It snakes beneath highway bridges, strip malls, nursing facilities and retirement centers, and it splits the uprights of the football stadium at the University of California, Berkeley.

"A lot of these structures are going to come down," said David P. Schwartz, chief of the USGS's Bay Area Earthquake Hazards Project.

He spoke with one foot on either side of the fault, marked by a crack that snaked through a parking lot in Hayward's business district.

Before San Francisco's Great Quake of 1906, on the San Andreas fault, there was the Great Quake of 1868 on the Hayward, a magnitude 6.9 rumbler that killed five people. Severe quakes have happened on the Hayward Fault every 151 years, give or take 23 years, meaning it is now into the danger zone.

Experts forecast the next big one will be in the potentially lethal 6.7 to 7.0 range. The Association of Bay Area Governments estimates it would wipe out some 155,000 housing units, 37,000 in San Francisco alone.

The ground on each side of the fault could shift 3 feet, meaning two objects on opposite sides could be abruptly carried a total of 6 feet apart, Schwartz said.

The Hayward Fault runs directly beneath Eden Jewelry and Loan, but the men working in the pawn shop shrugged when asked if they fear a quake.

"Honestly, it's a non-issue," said Saul Gevertz, 64.

The building was renovated about five years ago and now is essentially an enormous steel cage, designed to flex in an earthquake without breaking, said one of the building's co-owners, Darrell Davidson.

"I'm not worried-worried. I've thought about it," said Davidson, 47. "I think we're in good shape. I hope to God we are."

Nickey Avila acknowledged some alarm when informed that the fractures in the pavement outside his house were caused by the fault.

"I'm thinking one day it's going to move, but if I survive it, I'll be able to say I survived one of the biggest quakes of all time," said Avila, 23.

The quake could come at any moment.

"If it moved while we were walking, it wouldn't surprise me," Schwartz said during a tour of Hayward's misaligned street curbs, warped concrete gutters and abandoned buildings. They include the former Hayward City Hall, deemed too dangerous to occupy because it's right on the fault.

The City Hall was built in 1930, during an unusually quake-free period after the Great Quake of 1906 released stress on all faults in the region.

A "virtual tour" developed by the USGS shows the Hayward Fault slashing through identifiable structures, like DeMuynck's house, but she is resolved not to worry.

"There's dangers all around us, all the time, so if we thought about those dangers all the time, we wouldn't have anything else to think about," said DeMuynck, 62. "We just come home and say, 'The house is still here.' We're OK for another day."