The owners of a common type of wood frame building vulnerable to collapse in an earthquake would have five years to shore up those structures under a mandatory retrofit plan unveiled by Los Angeles Mayor Eric Garcetti on Monday.
So-called soft-story buildings have few structural supports and large open spaces on their first floors, making them more likely to pancake during strong shaking.
There are an estimated 16,000 soft-story buildings in Los Angeles, and many of those are apartment buildings.
"The biggest risk to our lives is posed by our older buildings," noted USGS seismologist Lucy Jones, who advised the mayor's office on this topic.
The retrofit plan is part of a larger report also released Monday assessing L.A.'s ability to rebound from a major earthquake.
"Today ladies and gentlemen we make history," said Mayor Garcetti of the new plan, titled "Resilience by Design."
"For a long time Los Angeles has been the epicenter of seismic risk but today we are going to be at the epicenter of seismic preparedness as well."
A year in the making, the report was a collaboration among city officials, seismologists at the U.S. Geological Survey, engineers and representatives from private telecommunications companies, among others.
Along with soft-story retrofits, the report calls for mandatory reinforcement of so-called non-ductile concrete buildings.
These structures are considered among the deadliest types of buildings because of the way they are constructed.
They have less give than so-called ductile buildings, and therefore have less capacity to absorb major shaking. Under the plan, owners of these buildings would have 25 years to make necessary fixes.
Building owners have long resisted mandatory retrofits because of the costs associated with them. By some estimates it can cost hundreds of thousands of dollars to update larger non-ductile concrete buildings.
“We know it works,” Mayor Garcetti said of retrofit programs.
He noted that after the Sylmar earthquake in 1971, certain brick buildings were required to undergo retrofitting, and he said none of those buildings collapsed during the 1994 Northridge quake.
Garcetti estimated that costs for retrofits can range from $5,000 for simple soft-story structures to $15 per square foot for larger concrete buildings.
The mayor's plan includes possible ways to help building owners manage these costs and also calls for a state wide bond to help with preparedness efforts.
Among other findings in the report:
- The city should implement a voluntary seismic safety ratings system that would assign buildings anywhere from one to five stars depending on their ability to withstand earthquakes
- Develop an alternate water system for fighting fires, using recycled water and seawater
- Fortify the Los Angeles Aqueduct where it crosses the San Andreas Fault
- Use quake-resistant pipes when replacing aging water pipes
- Support efforts to pass a state bond measure to fund seismic upgrades
- Work with Internet service providers to share bandwidth during an emergency
- Shore up the power grid where it crosses the San Andreas Fault
- Develop a solar-powered citywide Wi-Fi backup Internet
- Fortify cell towers
"I think the mayor has taken a very bold and important step forward for the city," commented Ron Mayes with the U.S. Resiliency Council, the group that developed the rating system for the seismic safety of buildings.
Mayes was not part of the mayor's team, but he did advise Jones on how a rating system would work.
He noted that under a volunteer rating system, building owners with structurally sound spaces will likely promote their score similar to how LEED certified buildings tout their eco-friendly credentials.
However, owners of less sound buildings will likely display no rating what so ever.
"This report doesn't try to solve every earthquake problem in the city," noted Jones. "What we did was focus on the aspect that science has told us imperiled the future of Los Angeles."
She explained that the focus was insuring that people and businesses are able to stay in Los Angeles during the months long process of fixing critical infrastructure after a major quake.
This story has been updated.