Nevada is strengthening highway bridges to make them safer in earthquakes, but older brick buildings continue to be unsafe in temblors as large as those that recently hit central California and devastated Iran, officials said.
"No bridge or structure is ever really earthquake-proof," said Todd Stefonowicz, assistant chief bridge engineer at the Nevada Department of Transportation.
"For the last three years we've been working on retrofitting highway overpasses on Interstate 80. We want to keep them standing in moderate quakes and keep the damage to areas that are easily identified and repaired."
In 2001 and 2002, Nevada spent $2.4 million to retrofit nine bridges over I-80 through Reno.
Crews are working on five overpasses and ramps near the Spaghetti Bowl - the interchange of I-80 and U.S. Highway 395 - and next year are scheduled to begin a $1.3 million project to retrofit five I-80 bridges between Verdi and northwest Reno.
Nevada ranks third in the nation in earthquake activity, behind Alaska and California.
In 2001, researchers said there was a 34 percent to 98 percent chance that an earthquake of magnitude 6 or greater likely will rock the Reno-Carson City corridor within 50 years. A temblor of that magnitude likely would cause significant damage to unreinforced masonry buildings.
Unlike highway bridges, older buildings aren't being reinforced unless the owners decide to do so. Nevada, unlike California, doesn't require that local officials survey at-risk buildings and adopt laws requiring the structures be reinforced or torn down.
In Nevada, older buildings are not covered by newer building codes unless their use changes.
A 1993 University of Nevada, Reno study predicted that most Truckee Meadows commercial buildings erected after 1970 would sway but survive a magnitude 6.5 temblor like the one that rocked California's central coast recently, but many older masonry structures would crumble.
"Old masonry buildings are a problem anywhere," said Manos Maragakis, the chairman of UNR's civil engineering department. "They are the first to collapse."