August 24, 2014 Earthquake: Napa, Vallejo, California, United States

One person killed and at least 208 injured, 150 buildings severely damaged and 1,000 moderately damaged in Napa County. At least 49 people injured, 10 buildings severely damaged and 34 moderately damaged in Solano County. Minor damage to several roads and several water main and gas line breaks in Napa & Solano Counties. Electricity and water services disrupted in Napa, Solano & Sonoma Counties. Six fires occurred in Napa County destroying at least 4 buildings. At least 8 km of surface faulting with at least 46 cm of right-lateral and 15 cm vertical displacements observed. Total economic loss estimated at 400 million U.S. dollars. Felt (VIII) at Napa; (VII) at American Canyon, Vallejo and Yountville; (VI) at Crockett, Deer Park, Glen Ellen, Port Costa, Rodeo and Sonoma. Felt in many parts of central and northern California from Arcata to Bakersfield. Felt (II) at Reno, Nevada. Also felt at Carson City, Glenbrook, Incline Village, Minden and Sparks.

Tectonic Summary

The earthquake lies within a 70-km-wide set of major faults of the San Andreas Fault system that forms the boundary between the Pacific and North American tectonic plates. The persistent northwestward movement of the Pacific plate relative to North America primarily causes right-lateral slip across the major faults, but also causes deformation between the major faults. The ongoing complex deformation field is revealed by modern geodetic surveys and earthquake patterns as well as the regional geologic structure. The earthquake is located at the eastern shore of San Pablo Bay between two major active fault systems: the Hayward-Rodgers Creek Fault system on the west and the Concord-Green Valley Fault system on the east. The earthquake occurred near the well-known West Napa Fault, and the less well known Carneros-Franklin Faults, which juxtapose different suites of rocks.

Historically, in this region shaking sufficient to seriously damage structures at Mare Is occurred during the M6.8 1868 Hayward Fault earthquake, the M7.8 1906 San Andreas Fault earthquake, and particularly during the M6.3 1898 Mare Is earthquake. The 1898 earthquake may have occurred about 20 km to the northwest on the southern Rodgers Creek Fault.

The 1999 Working Group on California Earthquake Probabilities (WG99, 1999) concluded that Hayward-Rodgers Creek Fault system has a 32% probability of generating a large earthquake (M6.7-7.4) by year 2030, and the Concord-Green Valley Fault system has a 6% chance of generating a large earthquake (M≥6.7) in same period.

The earthquake occurred near the north shore of San Pablo Bay. The bayshore areas in the region are underlain by landfill and bay mud and have experienced disproportionately greater damage during historic earthquakes. Such damage is caused by soil failure in the fills and amplification of ground shaking by soft bay mud.

(above ref #13456)

M6.0 earthquake hit near Napa Valley Sunday, injuring at least 172 people and causing extensive damage, including fires sparked by burst gas lines...spokesman said that ~70,000 customers in Sonoma & Napa counties lost power during the earthquake (ref #11055)

Napa County officials Thurs […] placed damage estimates at $362 million in building, infrastructure and economic losses...More than 120 businesses in the wine and agriculture industry suffered $48 million worth of damage, according to a county news release. The estimate does not include loss in revenue due to business closures or lost inventory (ref #11057)

A 65-year-old woman suffered a head injury when a television struck her during last month's earthquake in California's wine country has died.(ref #11072)

$700 million damage (ref #1250)

$87 million of disaster losses, one death, and 200 injuries. (ref #13955)

$1 billion economic losses (ref #13727)