Scientists have computed a table of quake odds that will help emergency officials in Southern California warn the public quickly that the Big One may be imminent.

The U.S. Geological Survey scientists figured out the chances that a moderate jolt along the San Andreas Fault will be followed by a catastrophic quake. It computed those odds for jolts of different sizes and locations.When a moderate jolt does occur, the scientists will consult their canned forecasts and will warn state officials if the odds of a catastrophic quake striking within the following three days fall between 5 percent and 25 percent.

Armed with such a warning, state officials can tell the public and get emergency equipment in place, said scientists who unveiled the quake-prediction system Tuesday at a meeting of the American Geophysical Union.

"The idea is to let people know when the possibility exists of a larger earthquake on the next several days," said Jim Davis, California's state geologist.

A 1988 Geological Survey report said the Big One is at least 60 percent likely within 30 years somewhere along the southern San Andreas Fault, which runs past Los Angeles.

A 1980 Federal Emergency Management Agency report said such a quake could kill up to 14,000 people, hospitalize 55,000 and cause up to $17 billion in damage.