It could hit 2 million near Bay area with magnitude 6.7, more

New cracks appear in Elke DeMuynck's ceiling every few weeks, zigzagging across her living room. 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 21/2 inches from its latch, the 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.

Several faults lurk beneath the region, including the San Andreas Fault on the west side of the Bay area, but geologists say that 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 Tom Brocher, a seismologist with the U.S. Geological Survey.

The Hayward Fault runs through one of the country's most densely populated areas; experts said that 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 hilltop manors overlooking the bay to Hayward's humble flatlands. It snakes beneath bridges, strip malls and nursing facilities, and it splits the uprights of the football stadium at the University of California at Berkeley.

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

The last great quake on the Hayward Fault was the Great Quake of 1868, a magnitude 6.9 rumbler that killed five people. Severe quakes have happened on the Hayward every 151 years, give or take 23 years, meaning that it is now into the danger zone.

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