Napa County rattled by series of aftershocks

NAPA, Calif. (KABC) -- Napa County was rattled by a series of aftershocks Tuesday morning, the largest being a 3.9 that struck one mile northwest of American Canyon.

The 3.9-magnitude aftershock struck at 5:33 a.m. It was followed by a 2.7-magnitude aftershock at 5:35 a.m., a 2.8-magnitude aftershock at 6:12 a.m. and a 3.2-magnitude aftershock at 6:45 a.m.

California's wine capital is still recovering from Sunday's 6.0-magnitude earthquake, which is estimated to have caused at least $1 billion in property damage. Dozens of homes and buildings were destroyed or have been ruled too unstable to enter.

Building inspectors are now going door to door, tagging each structure and assessing every crack and crumble. Engineer Bob Glasgow says another jolt could easily collapse damaged buildings.

State officials like California Sen. Dianne Feinstein are pushing for an early warning system.

"Officials in Washington and along the West Coast should partner with the private sector to make an interoperable earthquake early-warning system a reality, and we should do so as soon as possible before a much larger earthquake strikes," Feinstein said.

The Associated Press contributed to this report.

PHOTOS: Damage from 6.0-magnitude earthquake in Napa