August 7, 2008

Stringent standards help Chino Hills community withstand recent earthquake

CHINO HILLS, Calif.

If an earthquake had to hit somewhere in densely populated Southern California, this relatively new suburb of 80,000 people was about the best place possible.

Buildings in the community boast the latest in plywood-reinforced walls, tied-down foundations, strengthened concrete and stronger welds.

Chino Hills is just a few kilometres from the epicentre of the recent magnitude-5.4 quake, yet it withstood the shaking with almost no damage at all. Other communities farther away saw fallen bricks, cracked walls and windows, warped door frames and broken water mains and gas lines.

One big reason: Chino Hills went up mostly in the 1990s and was built to the stringent earthquake standards that the state wants to see adopted everywhere across California before the Big One strikes.

“I was wandering around out there after the quake and it struck me that there’s no building there that’s more than 10 years old. They’re all built to the most recent codes, and I think that’s true of the whole Chino area,” said Lucy Jones, a seismologist with the U.S. Geological Survey.

Since the 1930s, California has gradually boosted its building standards. Each severe quake has prompted new rules, with the most recent major overhaul coming after the 1994 quake in the Northridge section of Los Angeles that killed 72 people.

After that disaster, the building code was amended to require, among other things, the use of plywood to reinforce sheetrock walls in homes. The new rules also prescribed a different way of welding steel that makes the welds less likely to become brittle and crack.

The quake last month proved to structural engineers that their work is paying off.

In Chino Hills, 50 kilometres southeast of Los Angeles, about 70 per cent of the homes date to the mid- to late 1990s, and the city doesn’t have a single unreinforced mortar building, said Winston Ward, the city’s chief building official. Most commercial buildings are no more than four storeys tall.

Some, including a newly built Hindu temple, have foundations that rest on a type of rubber-and-metal bumper to lessen swaying, he said.

Experts said the quake could have produced more damage if it had been centred elsewhere.

Only about 20 per cent of buildings statewide are constructed to the standards used in Chino Hills. Of the remaining 80 per cent, 40 per cent would suffer major damage during a severe earthquake and 10 per cent would collapse, said Chris Poland, chief executive at Degenkolb Engineers in San Francisco.

Associated Press

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