Quake Watch: is America Next on the List

　　Two major earthquakes have caused devastation in Haiti and Chile. Is America likely to get hit by a "Big One" anytime soon?
　　The devastating earthquakes in Chile and Haiti this year have North American seismologists looking again at the potential for similar quakes here at home. After all, the U.S. lies on several major fault lines, and has suffered strong earthquakes throughout its history. Following is a run-down of what we know about the likelihood of a major seismic event hitting the continental U.S.:
　　Is the USA at risk from a high magnitude quake?
　　Yes. According to former FEMA director James Lee Witt, an earthquake happening in the United States "is not a matter of if, it is a matter of when." The US Geological Survey (USGS) says the same thing.
　　What areas are most at risk?
　　According to geologist Thomas L. Holzer, two faults in the USA have the capacity to cause earthquakes of a similar magnitude to the Chilean quake. They are the Aleutian fault zone in Alaska and the Cascadia fault zone, which runs from northern California to Washington.
　　What about the San Andreas fault?
　　The other major Californian fault, which famously provoked the 7.1 magnitude earthquake in Santa Cruz in 1989, is a smaller fault which "appears to rupture along shorter segments and generate slightly smaller earthquakes," according to Holzer.
　　I don't live on the West Coast or in Alaska. Am I safe?
　　Not necessarily. Some seismic experts say the New Madrid fault, which runs along some of the main commercial ports on the Mississippi, "will move again in the next 50 years." If the result is anything like the quake of 1812 that was centered in New Madrid, Missouri, it could cause widespread destruction in Illinois, Indiana, Missouri, Arkansas, Kentucky, Tennessee, and Mississippi.
　　Have we had earthquakes as strong as Chile before?
　　Yes — stronger, in fact. The quake that hit Prince William Sound, Alaska in 1964 was 9.2 magnitude - the second strongest on record, according to the USGS. Since 1900, three of the world's ten strongest earthquakes have occurred in Alaska.
　　When is the next serious quake likely to happen?
　　There's no easy answer, unfortunately. One USGS expert, Brian Atwater, puts the risk of an earthquake in Washington at "about one in 10... across the next 50 years." Another study says there is a 99.7% chance of California suffering a quake of 6.7 magnitude over the next 30 years.
　　How much warning will we get?
　　If we're lucky, a few seconds. "We don’t have any good way to predict earthquakes," says Jim Dieterich, chair of the USGS National Earthquake Prediction Center. “In terms of short-term warning—from a few days or weeks—with high reliability, we’re just not there at this point." California's 2004 temblor occurred without a single precursive quake. But even seconds can be useful: In Japan, thanks to an innovative early warning system, trains stop as soon as a quake begins.
　　Are U.S. buildings earthquake-proof?
　　Not enough of them. Even though California instituted one of the "best building codes and construction practice in the world" after quakes in the 70s and 80s, more than 80% of its buildings were constructed before then. An Oregon study found that more than 1,000 state buildings — including schools and hospitals — would be vulnerable to collapse in a major quake. And the impact of even a "moderate" (i.e 6.5 magnitude) quake in the Central and Eastern US is of "real concern," according to seismologist Mary Lou Zoback. In the unlikely event of one hitting New York City, it could cause "more than $1 trillion" in damages and an untold number of deaths.
　　Can our infrastructure withstand a quake?
　　No, and this would be where a large earthquake would have the most effect. The American Society of Civil Engineers said last year that 26% of the nation's bridges are "structurally deficient," which means that many would be destroyed by even a minor quake. "We have plenty of buildings that fall down on their own, even without earthquakes," one engineer told USA Today.
　　What are doing to make ourselves more prepared?
　　Oregon and Washington are both spending millions on retrofitting schools, bridges, highways and state buildings to withstand earthquakes. Meanwhile seismologists are working to improve their "earthquake forecasts."
　　Do the recent earthquakes increase the chances of one in the USA?
　　Experts say no, though evidence suggests that severe earthquakes may provoke temblors some years later. The Chilean quake last weekend might well have been caused by deep stresses in the earth's crust caused by the 9.5 quake that hit the country in 1960.