The seismically vulnerable San Bernardino City Hall will be closed through Tuesday in response to a heightened earthquake risk in Southern California, city officials said.
The decision to close City Hall on Monday and Tuesday comes in response to a swarm of earthquakes in the Salton Sea area last week, which temporarily increased the likelihood of a major earthquake in Southern California.
According to the U.S. Geological Survey, as of last Tuesday, the chances of a magnitude 7 or greater earthquake being triggered on the southern San Andreas fault over the following seven days were as high as 1 in 100 and as low as 1 in 3,000. Without the swarm, the average chance for such an earthquake striking on any given week is 1 in 6,000.
That seven-day period ends Tuesday morning.
Mark Scott, San Bernardino's city manager, said the City Hall building, which is close to the San Andreas fault, has never closed before because of the possibility of an earthquake.
"But we haven't had an alert like this either," he added. "We're not trying to suggest that the alert is an impending catastrophe. We're just trying to use an abundance of caution. We care about the safety of the public and our employees."
The city has been actively working on plans to vacate the building within the next few months, because of longstanding worries over how the building would fare in an earthquake, Scott said.
"The problem we've got is that our City Hall has got some real seismic issues associated with it," he said. "We're actively working on getting our employees out of that building."
The City Hall building was constructed before the Sylmar earthquake in 1971, according to Scott. After that earthquake, he said, seismic codes changed significantly.
"Other earthquakes have changed California seismic codes even further, to the point where the current City Hall building in San Bernardino is an example of everything you would not build today," Scott said.
A 2007 report noted the potential instability of the seven-story building in the event of a major earthquake, Scott said.
The estimated cost of retrofitting the building is more than $20 million, Scott said.
"For a bankrupt city that's a tough challenge," Scott said. "We're looking at alternative approaches rather than doing $20 million worth of work."
The plan is to move staff out of the City Hall building and into temporary facilities for a year or two, before eventually moving into city-owned facilities, Scott said.
San Bernardino has one of the largest concentrations of unreinforced masonry buildings in the state that are at risk of particularly intense ground motion.
"I was shocked to hear that, because I've been in several other cities and a lot of cities did this 30 years ago," Scott said.
The City Hall building will reopen on Wednesday. A Monday council meeting was rescheduled to Oct. 10.
Times staff writer Rong-Gong Lin II contributed to this report.
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