Cat Firm Issues Update on August Napa Quake in California

A brief issued on the August 2014 South Napa earthquake shows damage estimates of insured losses likely to be less than $100 million, yet total damages from the event approached $1 billion.

Catastrophe modeling firm Karen Clark & Co. issued a brief on the quake, which updated earlier estimates on damage released by the Boston-based firm.

“Downtown Napa experienced the highest ground motion and the most damage from the South Napa earthquake,” the brief states. “Damage was exacerbated by the fact that many of the homes are older construction and not built to the current code.”

Cripple walls without adequate bracing led to homes shifting off their foundations, and according to the City of Napa more than 1,500 residential units were damaged with close to 10 percent suffering severe damage or complete destruction. In total, 130 buildings were red tagged and 1182 yellow tagged by Napa building inspectors, the brief shows.

Many commercial buildings experienced significant damage to façades and building ornamentation, according to the brief.

“Perhaps most surprising in this earthquake, several newly constructed commercial buildings suffered more extensive damage than nearby older construction due to exterior decorative finishings that are particularly vulnerable to earthquake ground motion,” the brief states. “In addition, retrofitting was not as effective as expected in numerous cases. Even if a building is retrofitted, the deterioration of the mortar between bricks can cause weak joints within the (unreinforced masonry) walls resulting in partial wall collapse.”

Significant damage was also reported in Brown’s Valley, another town close to the fault rupture.

Peak ground motions were nearly as high as downtown Napa, but the nature and extent of damage were less likely do to the newer construction present in the area, the brief states.

Further from the rupture, in American Canyon and Vallejo, damage was primarily confined to minor wall cracks and chimney damage, according to the brief.

The City of Napa alone has estimated the damage from the earthquake at $362 million with an additional $80 to $100 million in losses to the wine industry, and the firm estimated $800 million for the entire county of Napa and $150 million for the city of Vallejo in Solano County.

South Napa Earthquake Report