Winemakers in California's storied Napa Valley woke up to thousands of broken bottles and barrels as a result of the earthquake.
The earthquake couldn't have come at a worse time for the region, which has just started harvesting the 2014 crop.
"It's devastating. I've never seen anything like this," said Tom Montgomery, a winemaker for B.R. Cohn Winery in Glen Ellen, California.
The epicentre of the 6.0-magnitude earthquake that struck Northern California, the strongest in the area in 25 years, was just six 10 kilometres southwest of Napa, California, the centre of California's winemaking region.
B.R. Cohn lost "as much as 50 per cent" of its wine, Montgomery said. The winery focuses on high-end, single estate wines that retail between $US40 ($A43.30) and $US100 ($A108.20) a bottle.
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"It's not just good wine we lost, it's our best wine," he said.
At Dahl Vineyards in Yountville, California, a rack full of wine barrels was teetering and in danger of coming down.
One barrel containing $US16,000 worth of pinot noir fell and was lost as a result of the quake.
The owners were trying to save the rest, removing the barrels with a forklift.
Elsewhere in the region, red wine stains were visible outside the doors of a warehouse - indicating there was damage inside.
Other wineries reported more modest damage.
In Oakville, Silver Oak Winery lost "a couple hundred bottles" of wine, said Ian Leggat, a spokesman for Silver Oak, as well as three barrels full of wine.
Most of the product damaged at Silver Oak was single-vineyard wines the winery uses for testing. None of the wines sold to consumers were damaged in the quake, Leggat said.
Even the wine in barrels that wasn't damaged by the quake may have problems, however, because wines aging in barrels are supposed to be kept as still as possible, Montgomery said.
Napa is California's best-known winemaking region. While it produces only four per cent of California's total wine crop, Napa's wines are considered among the best in the world and sell for a premium price.
The Napa Valley does $US50 billion in economic activity a year, or roughly a quarter of wine industry for the entire US, according to Napa Valley Vinters.
The earthquake adds to what has already been a difficult year for California winemakers.
California is in the middle of its worst drought in decades, and the earthquake comes just as winemakers in the region are getting ready to harvest the 2014 crop.
Winemakers were reporting modest damage to equipment, which could affect harvesting.
