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Napa Earthquake Reconnaissance Report

A magnitude Mw 6.0 affected the northern portion of the San Francisco Bay Area at 3:20 AM on 24 August 2014. SPA’s Charles Scawthorn visited the affected region, examined buildings and lifelines, spoke with fire departments, utility operators, and others. Shaking in some places reached design-level (fairly rare) motion, up to 5 times what would have been calculated for an earthquake of this magnitude. The earthquake caused one fatality and about 13 hospital admittances in Napa, with several hundred people requiring medical assistance.  In the historic city of Napa, it caused substantial damage to ordinary buildings, and very heavy damage to a number of historic masonry buildings, although some retrofitted masonry buildings had very little or no damage.  Approximately 116 buildings were red-tagged (unsafe to enter or occupy) and over five hundred yellow-tagged (limited entry), meaning that 2% of the Napa building stock was impaired by this not-very-rare earthquake.  Infrastructure was variously affected, with perhaps the water system having the most damage, with approximately 160 water main breaks.  Similar damage has been observed in several historic California earthquakes; some of it could have been readily prevented. See our publications page for the report.