Chilean earthquake hints at dangers of 'Big One' for USA
By William M. Welch, Dan Vergano and Chris Hawley, USA TODAY
One of the really "Big Ones" to shake the United States was a magnitude-9.0 earthquake along the Pacific Northwest coast more than 300 years ago, before the arrival of huge numbers of people and development, that sent a catastrophic tsunami to Japan.
Were something like that 1700 quake to occur today — and it certainly could, seismologists say — enormous destruction and loss of life would result in a region that is home now to big cities and millions of people.
The magnitude-8.8 earthquake that rocked Chile and sent tsunami fears across the Pacific on Saturday — nearly seven weeks after the enormously deadly quake that destroyed parts of Haiti— serves as a vivid reminder of the perils posed to the United States by countless fault lines and shifting plates.
"It's not a matter of if, only of when an event like this strikes the people of the United States," says Marcia McNutt, director of the U.S. Geological Survey. "Shame on us if we don't prepare."
As of Sunday, the death toll from the earthquake in southern Chile stood at about 700.By comparison, the Jan. 12 earthquake in Haiti killed about 230,000 people, the Haitian government says.
Chilean officials said 500,000 houses were destroyed or badly damaged, and President Michele Bachelet said "a growing number" of people were listed as missing. Looters ransacked stores, and a curfew was imposed in Concepcion, where an estimated 60 people were trapped in a collapsed apartment building.
Haiti's earthquake was shallower and closer to a major city, Port-au-Prince, than was the Chilean quake, which accounted for much of the devastation in Haiti. Stricter building codes and better enforcement of them played a major role in reducing the loss of life in Chile, says Andres García, manager of AGR Analysis, a construction and building management company in Viña del Mar, Chile.
"Chile has been building according to the best standards in the world for at least 20 years," García says. "As the technology and techniques have gotten better, the rules have gotten stricter. And that's what has minimized the loss of life this time around."
Chile sits on the so-called "ring of fire," a system of geological faults that circles the Pacific Ocean, and is frequently rattled by earthquakes. In 1906, a magnitude-8.6 quake near Valparaiso killed 20,000 people. A magnitude-7.8 quake near Chillan killed 28,000 people in 1939.
The quake on May 22, 1960, near Valdivia shattered the records for the strongest quake ever. With a magnitude of 9.5, it sent tsunami waves racing through the Pacific to as far away as Japan and the Aleutian Islands of Alaska. About 5,000 people were killed.
After that quake, Chile imposed strict rules about the quality of building materials, García says. It also invested heavily in research to find weak points in the soil under major cities.
"Chile has one of the most modern building codes in the world, and now we're seeing how the rules pay off," says Juan Felipe Heredia, a Mexican civil engineer who has designed buildings in South America.
Chile's economic strength also gives it an advantage. It is the wealthiest country in Latin America, with a per-capita income of $14,700.
"In Chile, they've been preparing for this moment for a long time," says Uriel Texcalpa, an architecture professor at Mexico's Iberoamerican University. "Haiti is just beginning. They're starting from zero."
Chile offers more lessons for U.S. planners than Haiti does, McNutt says, given similarities in building codes and earthquake awareness. Although the U.S. has made preparations more stringently than anywhere else, McNutt sees an Achilles' heel in the aging U.S. infrastructure of bridges and overpasses.
"I look at the reports of collapsing bridges and highways in Chile and worry what would happen here," she says.
In 2009, the American Society of Civil Engineers warned that 26% of the nation's bridges "are either structurally deficient or functionally obsolete." The engineers' report, based on Department of Transportation figures, showed that one in three urban bridges are either broken or obsolete, and suggested a $17 billion yearly shortfall in maintenance spending nationwide.
"Clearly infrastructure is a legitimate worry," says geotechnical earthquake engineer John Christian of Waban, Mass., a member of the National Academy of Engineering. "Engineers worry that we have plenty of buildings that fall down on their own, even without earthquakes."
California's San Andreas fault poses a much-worried threat. Californians have focused on preparing for a Big One for more than a century, since a 1906 quake in Northern California motivated people to take the hazard seriously, says Susan Hough, geologist at the U.S. Geological Survey in Pasadena. A 1933 quake centered at Long Beach led to passage a year later of tougher building requirements for schools.
"Since that time, the building codes have continued to evolve as we learn more about what buildings are dangerous and how the ground shakes under earthquakes," she says.
State and local building codes have prevented new construction of the most vulnerable building styles, unreinforced brick or concrete structures, she says. The 1994 Northridge earthquake in the San Fernando Valley of Los Angeles exposed weaknesses in steel welds and buildings.
Now the biggest worry is widespread use of apartments built atop ground-level parking, with supporting poles that can give way in a quake of sufficient size, she says.
"People may be complacent about California," Hough says. "We haven't really seen a big earthquake that really tests the infrastructure."
Such a big quake may be overdue in the heavily populated Southern California region, says Jim Goltz, earthquake and tsunami program manager for the California Emergency Management Agency.
"We have hundreds of faults in Southern California, and we could have a really large earthquake on any of them," Goltz says.
Officials in California are also focusing on non-structural hazards that can be deadly in big quakes, such as big-screen televisions, water heaters, furniture and bookshelves that can become missiles in violent quakes.
This Oct. 21, California officials will hold their third annual "Great California Shakeout" event aimed at informing people what to do in such a quake. Their advice —"Drop, cover and hold on" — suggests people take cover under furniture to protect themselves from flying objects....
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