A magnitude-6.0 earthquake hit the Napa Valley at 3:20 a.m. Sunday — the strongest temblor in the San Francisco Bay Area in a quarter century — destroying both opulent and modest homes, rupturing dozens of water and gas mains and causing injuries — mostly minor — to more than 100 people.
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At least 120 people had been treated at the emergency room at Queen of the Valley Medical Center in Napa, said Vanessa deGier, a hospital spokeswoman. Most of the injuries were minor lacerations or abrasions caused by falling debris. But three patients were in critical condition, including a child who had been crushed by a falling fireplace. No deaths had been confirmed as of Sunday evening.
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Despite the widespread damage, scientists said California was fortunate to escape greater devastation from the earthquake, which exposed gaps in the state’s preparedness. The historic 1906 San Francisco earthquake was about 500 times larger than Sunday’s temblor.

“It is truly small — small compared to what California has experienced in its recorded history,” said Ross S. Stein, a geophysicist at the United States Geological Survey.