The magnitude-6.0 earthquake struck around 3:20 a.m., and for some awakened residents the temblor revived memories of the last big quake to strike the San Francisco Bay Area 25 years ago, which did major damage.
Gov. Jerry Brown declared a state of emergency for Napa, Solano, and Sonoma counties. Schools in Napa Valley were ordered closed Monday.
Mike Parness, city manager, said 15 or 16 buildings in the central downtown were "red tagged" after inspectors found damage left them too dangerous for people to enter. Several dozen other buildings were awaiting further evaluation.
"We've got a lot of workers out checking out homes and buildings,'' Parness said.
In the city's downtown section, a 10-foot chunk of brick and concrete was shaken from the corner of the old county courthouse building. Big pieces of rubble littered the lawn and street in front of the building.