LOS ANGELES -- Americans viewing the devastation caused by last week's earthquake in Colombia might be tempted to knock on wood. Wood-frame houses, the type generally built in the United States, can stand up far better in quakes than the outwardly solid masonry homes that crumpled so quickly in Colombia.
But even wooden homes can fall down, and each new earthquake adds to the understanding of what more could be done to make residential housing more quakeproof. Indeed, the Northridge, Calif., quake of 1994, prompted a re-evaluation of building codes when wood-frame buildings suffered far more damage than had been expected."Northridge showed they don't perform as well as we thought," said Bob Reitherman, executive director of California Universities for Research in Earthquake Engineering.
Still, home construction makes a big difference. In Colombia and other developing nations, homes are often made of unreinforced masonry, adobe or mud, and there are few residential building codes. Homes in wealthier parts of Armenia, presumably with better construction, did better.
Wooden frames generally do better in quakes because they have some flexibility. "If the structure doesn't give during the earthquake, then it tends to be completely destroyed," said Tom Henyey, a geological sciences professor at the University of Southern California.
But merely having a wood frame isn't enough, experts say. In Kobe, Japan, many older houses with wooden frames collapsed in a huge 1995 quake because they were not built to withstand lateral forces and had extremely heavy roofs made of traditional Japanese tiles.
To better withstand a quake, experts say, homes must have shear walls, which are normally made from plywood fastened between the upright wooden beams to help withstand side-to-side forces. The frame of the home should also be bolted to the foundation to make sure it doesn't slip off. And upper floors and roofs should be securely attached to floors below.