Napa Earthquake Shows Urgency of Building Retrofits
"Experts have long known that three types of construction common in the state don't hold up well in quakes: brick or stone, those with "soft" stories—floors not well-reinforced—and certain kinds of concrete structures. In California, new construction of such buildings has been banned," writes Alejandro Lazo.
But such buildings haven't disappeared, and efforts to retrofit those remaining aren't uniform. The state leaves enforcement of such measures in the hands of local jurisdictions.
Lazo describes the retrofit required for each type of aforementioned construction. Napa had passed a 2006 ordinance requiring retrofit of unreinforced masonry. All but about six of these types of buildings had undergone retrofit when the quake hit.
Building damage was widespread nevertheless. "On Monday (August 25), the city of Napa said that 64 buildings had been tagged 'red' by inspectors as unsafe to enter. More than 100 were tagged 'yellow, meaning they require further inspection," notes Lazo.
Lucile Jones, a seismologist with the U.S. Geological Survey, who has been hired by the city of Los Angeles to evaluate its buildings, said the structural damage from Sunday's quake "was extremely predictable." Dr. Jones, who advises the state commission on risk reduction, added: "We now have to make a choice to do something about it before the next earthquake hits."
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