Earthquake: How CA's seismic building codes compare to Taiwan's

118231 full
118231 full

Rescue crews in Taiwan are still searching for missing people after Saturday’s 6.4 magnitude earthquake near the city of Tainan that toppled about a dozen buildings, including a high-rise.

Experts say the damage would have been worse if it weren’t for Taiwan’s relatively modern building codes based on guidelines known as the Uniform Building Codes.

These seismic safety standards were developed in the U.S. and are used by California as well, says structural engineer Michael Cochran of Thornton Tomasetti Inc.  

The codes address which building materials and which designs are best for seismically active regions, he said.

However, not all governments use the codes in the same way. California for instance sometimes adds additional guidelines to its building standards, Cochran said.

Structural engineer Farzad Naeim studied Taiwan’s infrastructure after a major quake there in 1999. He said one problem in Taiwan is that not all contractors follow the codes accurately.

"The problem is implementation of the code, the problem is quality control," he said.

That means the guidelines may only be partially implemented, leaving buildings vulnerable despite codes' being in place.

Naeim also noted that for a time, Taiwanese construction crews used subpar materials like old oil cans to line columns and walls, though this was banned after the 1999 quake in  Nantou County, Taiwan.

"It seems that that was pretty common," he said, adding that many of the structures partly reinforced with oil cans are likely still standing and could come down in another quake.

Peter Yin is a Structural Engineer with the Port of Los Angeles and also studied the way buildings performed in the 1999 Taiwan quake.

He pointed out that buildings in Los Angeles are likely to do better during shaking in part because the city has good code enforcement.

"For example if you go to Building and Safety with a permit they are going to check your seismic design," Yin said. City inspectors are also supposed to follow up with contractors to make sure those designs are carried out properly.

One problem facing both L.A. and Taiwan though, is the number of older, vulnerable concrete buildings put up before the modern codes of the 1980s.

These are known as non-ductile concrete buildings and can collapse under strong shaking. Researchers from UC Berkeley said they identified around 1,500 such buildings in L.A.

The L.A. City Council passed an ordinance last year requiring retrofits of these structures, but it could take 25 years for the work to be completed.

L.A. Mayor Eric Garcetti said the recent Taiwan quake was a reminder of immense destruction a quake can cause.

"As we grieve, we must also remember how critical it is to prepare for the next big earthquake here at home, and take action now to protect Angelenos' lives and property," Garcetti wrote in a statement.

Assemblymember Adrin Nazarian also announced that he would be backing a series of budget measures for the 2016 - 2017 fiscal year centered on earthquake readiness.

Those include scaling up a prototype of an earthquake early warning system, increasing funding for the "Brace + Bolt"program that helps homeowners pay for retrofits and creating a five-year 30 percent tax credit for certain building owners looking to retrofit their structures.

There's no telling when Southern California might see a quake similar in size or larger than the one in Taiwan, but experts say it's only a matter of time.

A new study from UC Riverside added urgency to the matter, suggesting that earthquake ruptures can jump from one fault to another over larger distances than previously thought.

This could create "double quakes" that intensify damage across a region like Southern California.

blog comments powered by Disqus