A strong, magnitude 6.0 earthquake that occurred at 3:20 a.m. Sunday near Napa, CA, caused no fatalities but damaged a lot of older wineries and led to a loss of a lot of wine.
It was the largest earthquake to strike the San Francisco Bay Area since the 1989 magnitude 6.9 Loma Prieta Earthquake. However, on the Modified Mercalli Intensity (MMI) Scale, that means Sunday’s earthquake was only a little more than 1/10 as violent as the Loma Prieta Earthquake.
According to the natural hazard risk assessor CoreLogic, the earthquake was located about 6 miles southwest of Napa, at a depth of 7 miles on a yet-to-be identified northwest-oriented strike-slip fault production.
Napa Valley is one of the premier grape growing regions in the United States. Almost the entire valley is covered by a patchwork of vineyards and wineries. Representing 99% of the production of all Napa Valley appellation wines, the 500-member Napa Valley Vintners trade association estimates that Napa County annually contributes over $13 billion of economic activity.
CoreLogic expects that insured losses could range from $500 million to $1 billion, however, there is a fair amount of uncertainty.