"Obviously it's going to be a rough Christmas for people here in Paso Robles and the economic impact on the city has yet to be felt," said Paso Robles Mayor Frank Meacham on Tuesday.

Meacham and Dallas Jones, director of the state Office of Emergency Services, showed Schwarzenegger the scene where the quake demolished a historic clock tower building, a landmark in the community of nearly 27,000.

Schwarzenegger pointed to a severely damaged building on one side of a street and an intact building on the other side

"Here you can see very clearly the difference in a building that hasn't been retrofitted and one that has been retrofitted," said the governor, who stopped to shake hands with firefighters.

"Did you go to bed yet?" he asked them. "A couple of hours? Oh, that's good."

The fault system that unleashed the quake about 20 miles to the northwest of Paso Robles remained active: There had been more than 100 magnitude-3 or higher aftershocks by Wednesday morning.

The aftershock sequence was likely to continue for months and perhaps upward of a year, the US Geological Survey said. There was a 90 percent or greater probability that aftershocks of 5.0 magnitude or greater would follow in the next week.

Bad weather prevented helicopters from taking USGS scientists on aerial surveys Tuesday and there was no definitive evidence of a surface rupture of the fault, geologist Davis Schwartz said.

There was no immediate estimate of the total value of quake-related damage. A detailed analysis of damage was being developed, said Office of Emergency Services spokesman Dale Chessey.

Schwarzenegger's declaration of an emergency in San Luis Obispo County directs state resources to be made available to help. It also means inspectors will come to determine whether assistance should be sought from the Federal Emergency Management Agency or the Small Business Administration for low-cost loans for repair and recovery.

The quake's two fatalities, Jennifer Myrick, 20, of Atascadero, and Marilyn Zafuto, 55, of Paso Robles, were found on the street outside the 1892 clock tower, which pitched into the street and crushed a row of parked cars.