Architects and engineers who worked on John Wayne Airport's Thomas F. Riley Terminal had to design a building to serve 8.4 million passengers a year that sits virtually on top of the Newport-Inglewood earthquake fault, one of the most feared in California.
Located about 5 miles from the offshore fault, the new, $62-million terminal exceeds all state and local seismic safety standards, according to John McCarney, project manager for HPV, a consortium hired by Orange County to manage the $310-million airport expansion program.
Does that mean the building can withstand a magnitude 7.0 temblor?
"It's difficult to translate the standards we work with into something on the Richter Scale," McCarney explained, "but I think that's about right."
McCarney said the standards involve four types of earthquake zones, with Zone Four being the most dangerous. The new airport terminal is in Zone Four, so it had to meet the strictest standards, he said.
One way to think of it, he said, is that Zone Four buildings must be able to withstand quakes that generate lateral forces equal to 13.3% of their total mass. The new terminal was built to exceed that standard by 50%.
This means that if an object 20% as heavy as the building were to hit it on the side, it would not collapse but might have some cracking, according to Robin Shepherd, professor of civil engineering at UC Irvine.
"This is similar to the approach used for hospitals and fire stations," McCarney said.
To achieve such standards, oversized steel components were used in construction, providing additional structural resistance.
Also, although the terminal building looks monolithic, internally it consists of several independent, free-standing structures to minimize earthquake damage.
McCarney pointed to how well skyscrapers survived the October, 1989, Loma Prieta earthquake in the San Francisco Bay Area. They suffered only minor damage.
"Steel has the ability to yield and still retain a higher percentage of its structural strength," McCarney said.