The 2014 South Napa earthquake occurred in and around the city of Napa, California on August 24 at 3:20 a.m. local time, measuring at 6.0 on the moment magnitude scale. The tremor’s epicenter was located south of Napa, approximately 3.7 miles (6.0 km) northwest of American Canyon near the West Napa Fault, beneath the Napa Valley Marina on Milton Road, just west of the Napa County Airport.
The earthquake was the largest in the San Francisco Bay Area since the 1989 Loma Prieta earthquake. Significant damage and several fires were reported in the southern Napa Valley area, and there was also damage in the nearby city of Vallejo, in Solano County. The quake killed one person, injured about 200, and interrupted power to more than 69,000 Pacific Gas and Electric Company customers. An experimental earthquake warning system alerted seismologists ten seconds before the quake. On September 11, 2014, U.S. President Barack Obama declared the earthquake a major federal disaster. Early estimates by California officials indicated that the earthquake caused over $400 million in damage.
The main earthquake was magnitude 6.0, with a depth of 10.7 km. The United States Geological Survey (USGS) estimated 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. The earthquake lasted 10 to 20 seconds, depending on location. At least twelve aftershocks followed, including one of magnitude 3.9. The earthquake was the largest earthquake in the Bay Area since the magnitude 6.9 Loma Prieta earthquake of 1989. Governor Jerry Brown declared a state of emergency shortly after the earthquake due to the severe damage and the possibility of aftershocks.