USA Update Aftershocks rattle Napa Valley: What causes them?

As many as 65 aftershocks occurred in the first 24 hours following Sunday’s quake, and four minor temblors were reported in Napa County Tuesday morning.

By , Staff writer

Eric Risberg/AP Photo

The 6.0-magnitude earthquake that rocked the Napa Valley in California over the weekend, causing dozens of injuries and extensive damage in the city of Napa, delivered several encore performances Tuesday in the form of aftershocks.