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.

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