What Will Happen When "The Big One" Hits California?

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What happens when a big earthquake - or "The Big One" - hits Los Angeles depends on where the earthquake hits and how strong it is. Still, scientists have developed models and speculated on what could happen in a worst-case scenario - and it's not very pretty.

The term "The Big One" can mean a lot of different things, so it's important to separate the hyperbole from the facts. The danger of a large earthquake in Los Angeles, aside from its strength, is the shape and makeup of the L.A. basin. Essentially, Los Angeles is surrounded by mountains that form a large bowl of bedrock. Over millions of years rock and sand have collected in that bowl - and that's the compacted surface on which Los Angeles rests. It?s a bit like a bowl of Jell-O.

When an earthquake hits, its waves will reverberate, sway and jiggle a lot more on L.A.'s type of loose ground. This phenomenon, a recent MIT and Stanford study claims, could be the most disastrous aspect of an earthquake in Los Angeles. They estimate that Downtown L.A. - the area with the most skyscrapers - will feel the shaking three times as much as other areas.

In 2008, hundreds of scientists worked in a comprehensive report detailing the impact of a 7.8 scale earthquake. They estimated that it would last three minutes, or 15 times longer than the legendary 1994 Northridge earthquake. There would be close to 1,800 casualties, 50,000 injured, 1,600 fires, and about $200 billion in damage - on scale with Hurricane Katrina. In other words, it might not be the "San Andreas" movie, but in some respects it?s not far off, either.

While seismologists can't yet predict earthquakes, they can certainly help cities prepare. And this report, without a doubt, has pushed leaders to overhaul Los Angeles's preparedness. As they say: it's not a matter of "if," but "when."