USGS nearly doubles California's odds of massive, 8.0 earthquake

The chances that California will be rocked by a magnitude 8.0 earthquake or greater in the next 30 years was just bumped up to 7 percent, from 4.7 percent, the U.S. Geological Survey said on Tuesday. That would be really bad news, especially if the Big One hit near a population center — an 8.0 earthquake would produce 89 times the energy of a magnitude 6.7 Northridge temblor that shook Los Angeles in 1994, and similarly more powerful than the 6.9 magnitude Loma Prieta that rattled the Bay Area in 1989.

The reason for the boosted odds is that the USGS used to think "faults were separate and isolated," USGS seismologist Ned Field tells the Los Angeles Times, but it has become increasingly clear that California has a "vast interconnected fault system," and that a quake on one fault can jump to another. A 7.2 earthquake that hit Baja California in 2010 probably jiggled at least six faults, putting Southern California at greater risk.

The USGS isn't predicting when the Big One will hit, just that it's more likely to than previously thought. "The message to the average citizen hasn't changed," said Field, the lead author of the USGS's new report. "You live in earthquake country, and you should live every day like it's the day a Big One could hit." So why focus on the next 30 years? The LA Times explains: "It's the typical term a homeowner is paying off the mortgage on a house." Now you know.

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