(CNN) -- A 6.0-magnitude earthquake struck Northern California early Sunday, the U.S. Geological Survey said.
In Napa, at least 120 people were injured and treated in the emergency room of Queen of the Valley Hospital, said Hospital president Walt Mickens.
Six patients sustained critical injuries, including a young child, Mickens said.
The child was hurt when a fireplace collapsed and has been airlifted to UC Davis Medical Center, hospital spokeswoman Vanessa deGier told CNN.
"The majority of injuries that we are seeing are non-life-threatening, but still serious," she said. "Lots of lacerations and abrasions, obviously from fallen debris."
It was the strongest earthquake to hit the Bay Area since 1989, when a quake struck during the World Series. Gov. Jerry Brown declared a state of emergency.
Sunday's earthquake struck four miles northwest of American Canyon, six miles southwest of Napa and nine miles southeast of Sonoma, according to the USGS.
At least 60 minor water main breaks and leaks were reported, and 20 of those lines have been shut off, according to Napa public works director Jack Rochelle.
"None of our larger transmission mains appear to have been damaged. That is really good news," Rochelle said.
He said it might take up to a week to get the water system back to normal. The water that is still flowing is safe to drink, he said.
The earthquake triggered six major fires, including several mobile homes that completely burned down, (Napa Fire Chief John) Callanan said. The city has set up a shelter for those who have lost their homes.
People phoned in more than 100 reports of gas leaks and downed power lines, according Napa city officials.
Some historic buildings in downtown Napa showed extensive damage and at least 15,000 customers in and around Sonoma, Napa, and Santa Rosa lost power, according to Pacific Gas and Electric Company.
How did it feel?
The USGS estimated, based on their locations, that 15,000 people experienced severe shaking, 106,000 people felt very strong shaking, 176,000 felt strong shaking and 738,000 felt moderate shaking.
For those in Napa, close to the epicenter, the quake jolted downtown residents such as Karen Lynch.
"It was not like other quakes we have felt," Lynch told CNN. "This was a violent quake."
Farther south of the epicenter in San Francisco, CNN producer Augie Martin felt the quake differently.
"It was a fairly good shake, about 25 or 30 seconds. It was a softer rolling type earthquake " he said.
The quake struck about 7 miles deep and was considered "strong" by the USGS. Major quakes start at a 7.0 magnitude, according to the USGS scale.
The economic loss caused by the quake is likely to be more than a billion dollars, according to USGS pager data.
Wine country hit
"I've got a lot of broken wine, being here in Napa," said Emily Massimi, who was woken up by the quake. "We tend to collect wine, so I have wine all over my kitchen, and glass, and pictures off the wall and books off of bookshelves," she told CNN.
At Silver Oak Winery, owner David Duncan spent the morning cleaning up hundreds of broken wine bottles that fell off the shelves.
"Those bottles were very unique," he said. They were part of his private collection and worth hundreds of dollars. Duncan said he plans to open the winery today.
There have been over 60 aftershocks, according to the USGS, ranging from 0.6 to 3.6 magnitude.
CNN's Rick Martin contributed to this story
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