(NAPA, Calif.) -- Northern California is cleaning up Monday, one day after suffering its strongest earthquake in 25 years.
A state of emergency remains in effect following the South Napa Earthquake, which struck about 3:20 a.m. local time Sunday, according to the U.S. Geological Survey -- catching many people sound asleep, sending dressers, mirrors and pictures crashing down around them.
The jolt injured more than 100 people, buckled roads and damaged historic buildings in the heart of the state’s wine country. A 13-year-old was critically injured by a crumbling fireplace.
Damage from the earthquake could reach $1 billion, according to EQECAT, a company that studies catastrophe risk.
The earthquake’s epicenter was located about six miles south-southwest of Napa, California, and 51 miles west-southwest of the state capital, Sacramento. Officials have variously referred to the earthquake's magnitude as 6.0 and 6.1.
The earthquake was the largest one to shake the Bay Area since the 1989 6.9-magnitude Loma Prieta Earthquake. Dozens of aftershocks followed.
Residents remain worried about the potential for further aftershocks. Many people stayed outside Sunday night, not wanting to go into their homes for fear of a follow-up tremor.
Pacific Gas and Electric Company initially showed more than 15,000 customers without power, primarily in Napa, Sonoma and Santa Rosa Counties.
Several buildings in Napa were damaged or on fire in the wake of the earthquake, ABC News station KGO in San Francisco reported. Fires also flared in a mobile home park where four homes were destroyed and two others were damaged, officials said.
Napa City Manager Mike Parness said at least 15 buildings will need to be inspected or repaired before they can be occupied again.
John Callanan of the Napa Valley Fire Department said firefighters received more than 100 calls from people who smelled natural gas.
"Our resources are exhausted as far as quantity of on-duty personnel," he said.
Dozens of water main leaks were also reported, although city officials said the water was safe to drink.
At least 120 people were treated at Queen of the Valley Medical Center in Napa, hospital officials told ABC News. Only a handful of patients needed to be hospitalized.
Six of those people suffered critical injuries, including the teen hurt by the fireplace, who was flown to UC Davis Medical Center for further treatment, said hospital president Walt Mickens. The teen was in serious condition as of Sunday night.
All schools in the Napa Valley Unified School District will be closed Monday. Justin Siena High School will also be closed.
Historic buildings damaged by the earthquake included Sam Kee Laundry, Goodman Library and the Napa County Courthouse, the city said, adding that two commercial buildings also suffered severe damage.
Napa County Supervisor Bill Dodd said he believed the county courthouse had been retrofitted for earthquakes.
"I've been through a few of these and I've never seen anything like this, particularly in downtown Napa," Dodd told ABC News. "The county building is just in total disrepair, and they've moved it down to the sheriff's office -- so that's where the coordinating all the emergency services for the county."
President Obama was briefed on the earthquake, a White House spokesman said.
The earthquake’s impact was especially powerful on the region’s wine industry, with vineyards reporting busted barrels and smashed bottles. Andrew Brooks at Bouchaine Vineyards says the damage is costly.
“Fifty barrels worth of wine, 3,000 gallons,” Brooks said of the damage. “It’s expensive, in the tens of thousands of dollars for sure.”
Dozens living in the region reported falling dishes and violent shaking inside their homes.
"I was alone in the house so I didn't know what to do -- and the first thing when it stopped I ran under the table and tried to get cover because it's the first thing they say to do for an earthquake is get under the table," Diana Martini, who lives in Vallejo, California, told ABC News.
Martini said her television crashed to the ground, along with some of her dishes.
"I'm on the first floor, so that was the scariest thing. I thought the building was going to come down," she said.
Anne Whitlock, who lives in Napa, says her family’s home may have collapsed on them if not for earthquake retrofitting.
“We spent thousands of dollars putting in a 25-foot steel beam, and $50,000 worth of piers under the house to make it earthquake-safe, and I do think that's what saved us,” Whitlock told ABC News.
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